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Leptin released by adipocytes has been implicated in the control of food intake but recent detection of specific leptin receptors in the pancreas suggests that this peptide may also play some role in the modulation of pancreatic function. This study was undertaken to examine the effect of exogenous leptin on pancreatic enzyme secretion in vitro using isolated pancreatic acini, or in vivo in conscious rats with chronic pancreatic fistulae. Leptin plasma level was measured by radioimmunoassay following leptin administration to the animals. Intraperitoneal (i.p.) administration of leptin (0.1, 1, 5, 10, 20 or 50 microg/kg), failed to affect significantly basal secretion of pancreatic protein, but markedly reduced that stimulated by feeding. The strongest inhibition has been observed at dose of 10 microg/kg of leptin. Under basal conditions plasma leptin level averaged about 0.15 +/- 0.04 ng/ml and was increased by feeding up to 1.8 +/- 0.4 ng/ml. Administration of leptin dose-dependently augmented this plasma leptin level, reaching about 0.65 +/- 0.04 ng/ml at dose of 10 microg/kg of leptin. This dose of leptin completely abolished increase of pancreatic protein output produced by ordinary feeding, sham feeding or by diversion of pancreatic juice to the exterior. Leptin (10(-10)-10(-7) M) also dose-dependently attenuated caerulein-induced amylase release from isolated pancreatic acini, whereas basal enzyme secretion was unaffected. We conclude that leptin could take a part in the inhibition of postprandial pancreatic secretion and this effect could be related, at least in part, to the direct action of this peptide on pancreatic acini.

Background: Recent studies clearly demonstrate that Helicobacter pylori (H. pylori) infection of the stomach causes persistent elevation of ammonia (NH3) in gastric juice leading to hypergastrinemia and enhanced pancreatic enzyme secretion., Methods: The aim of this study is to evaluate the influence of NH4OH on plasma gastrin level and exocrine pancreatic secretion in vivo in conscious dogs equipped with chronic pancreatic fistulas and on secretory activity of in vitro isolated acini obtained from the rat pancreas by collagenase digestion. The effects of NH4OH on amylase release from pancreatic acini were compared with those produced by simple alkalization of these acini with NaOH., Results: NH4OH given intraduodenally (i.d.) in increasing concentrations (0.5, 1.0, 2.0, 4.0, or 8.0 mM/L) resulted in an increase of pancreatic protein output, reaching respectively 9%, 10%, 19%, 16% and 17% of caerulein maximum in these animals and in a marked increase in plasma gastrin level. NH4OH (8 x 0 mM/L, i.d.) given during intravenous (i.v.) infusion of secretin (50 pmol/kg-h) and cholecystokinin (50 pmol/kg-h) reduced the HCO3 and protein outputs by 35% and 37% respectively, as compared to control obtained with infusion of secretin plus cholecystokinin alone. When pancreatic secretion was stimulated by ordinary feeding the same amount of NH4OH administered i.d. decreased the HCO3- and protein responses by 78% and 47% respectively, and had no significant effect on postprandial plasma gastrin. In isolated pancreatic acini, increasing concentrations of NH4OH (10(-7)-10(-4) M) produced a concentration-dependent stimulation of amylase release, reaching about 43% of caerulein-induced maximum. When various concentrations of NH4OH were added to submaximal concentration of caerulein (10(-12) M) or urecholine (10(-5) M), the enzyme secretion was reduced at a dose 10(-5) M of NH4OH by 38% or 40%, respectively. Simple alkalization with NaOH of the incubation medium up to pH 8.5 markedly stimulated basal amylase secretion from isolated pancreatic acini, whereas the secretory response of these acini to pancreatic secretagogues was significantly diminished by about 30%. LDH release into the incubation medium was not significantly changed in all tests indicating that NH4OH did not produce any apparent damage of pancreatic acini and this was confirmed by histological examination of these acini., Conclusions: 1. NH4OH affects basal and stimulated pancreatic secretion. 2. The excessive release of gastrin may be responsible for the stimulation of basal pancreatic enzyme secretion in conscious animals, and 3. The inhibitory effects of NH4OH on stimulated secretion might be mediated, at least in part, by its direct action on the isolated pancreatic acini possibly due to the alkalization of these acini.

Objectives: To determine whether detrusor muscle strips from a male rat with infravesical outflow obstruction model demonstrate supersensitivity to parasympathomimetic and neurokinin NK-1 and NK-2 selective agonists., Methods: Bladder instability developed after 6 weeks of partial urethral obstruction. The micturition frequency and voided volume were determined in unanesthetized animals. Detrusor hypertrophy was confirmed by evaluation of bladder weight. In vitro organ bath was used to compare the affinity and maximal activity of bethanechol and neurokinin NK-1 and NK-2 selective agonists on strips from the detrusor muscle of sham and obstructed rats. Bethanechol, N-Ac[Arg6, Sar9, Met(O2)]-SP(6-11), and [beta-Ala8]-NKA(4-10) were used to characterize cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Results. No significant differences in affinities and maximal responses were found using 10-mg detrusor muscle strips with each of the three agonists., Conclusions: Bladder instability produced by outlet obstruction does not involve changes in the affinity or maximal activity of cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Furthermore, detrusor supersensitivity to neurokinins or bethanechol was not seen. This suggests that bladder instability is not due to an increased affinity or maximal response to neurokinins or parasympathomimetics.

Conclusion: Stimulation of pancreatic sensory nerves by capsaicin produced secretory effects probably caused, at least in part, by the release of CGRP., Background: In the pancreas calcitonin gene-related peptide (CGRP) has been localized in the sensory nerves, but its physiological role is unknown. This study was undertaken to compare the changes of pancreatic enzyme secretion produced by CGRP and by stimulation or destruction of sensory nerves., Methods: To stimulate sensory nerves, low doses of capsaicin (0.25-0.5 mg/kg) were given intraduodenally to the conscious rats with chronic pancreatic fistula. To inactivate sensory nerves high doses of capsaicin (100 mg/kg) were given subcutaneously 10 d before tests. For the in vitro experiments pancreatic slices and isolated pancreatic acini were prepared from intact and capsaicin-denervated rats., Results: In conscious rats, CGRP given subcutaneously (5-10 micrograms/kg) and low doses of capsaicin given intraduodenally reduced basal pancreatic secretion. In isolated pancreatic acini, CGRP (10(-10)-10(-6) M), but not capsaicin, increased basal or secretagog-stimulated amylase release. In pancreatic slices (containing nerve fibers) capsaicin (10(-10)-10(-6) M) increased enzyme secretion, and this secretion was abolished by previous inactivation of sensory nerves by this neurotoxin. Capsaicin deactivation did not affect the secretory response of pancreatic acini to CGRP, cerulein, or urecholine. Sensory denervation by capsaicin did not change basal protein secretion, but reduced that produced by feeding or diversion of pancreatic juice to the exterior during first 2 h of the tests.

The effect of intravenous administration of baclofen, a GABA(B) receptor agonist, on gastric acid secretion from perfused stomach was studied in vagotomized rats anesthetized with urethane. Baclofen did not stimulate acid secretion by itself. In contrast, baclofen dose-dependently potentiated acid secretion induced by pentagastrin, bethanechol and direct vagal stimulation, but not by histamine. Baclofen-potentiated acid secretion induced by pentagastrin and bethanechol was not influenced by pretreatment with atropine or cimetidine, respectively. Baclofen-potentiated acid secretion evoked by direct vagal stimulation was prevented by pretreatment with proglumide which is a gastrin receptor antagonist. Baclofen-potentiated acid secretion evoked by bethanechol was partly prevented by bicuculline methiodide which is a GABA(A) receptor antagonist, but not by phaclofen which is a GABA(B) receptor antagonist, suggesting an involvement of peripheral GABA(A) receptors. Baclofen-potentiated acid secretion induced by direct vagal stimulation was not affected by the change of body temperature. These results suggest that baclofen stimulates acid secretion under certain conditions, and that two mechanisms are involved in this effect. The effects of baclofen on acid secretion may be mediated by increasing the release of histamine by pentagastrin, bethanechol and direct vagal stimulation. In addition, baclofen would also be effective if muscarinic agents were already occupying muscarinic acetylcholine receptors on parietal cells.

L-Arginine (L-Arg), that is a substrate for nitric oxide (NO) synthase, stimulates the release of pancreatic islet hormones but the mechanism of this stimulation is unknown. The aim of this study was to determine the role of NO in the control of endocrine and exocrine pancreatic secretion in response to sham feeding (SF), ordinary meat feeding (F), duodenal perfusion with nutrients and i.v. infusion of gastrin releasing peptide (GRP) or urecholine in conscious dogs with chronic pancreatic fistulas. SF1 F, duodenal nutrient and GRP and urecholine resulted in the stimulation of pancreatic secretion reaching, respectively, 50%, 50%, 40%, 85% and 20% of maximal response to caerulein (200 pmol/kg-h i.v.). Infusion of L-Arg (50 mg/kg + 5 mg/kg-h i.v.) almost doubled the basal pancreatic protein secretion and significantly increased the secretory response to SF, F, and duodenal nutrient. After i.v. administration of L-NNA (2.5 mg/kg + 0.5 mg/kg-h), an inhibitor of NO synthase, the pancreatic secretory responses to SF, F, duodenal nutrient, GRP and urecholine were significantly inhibited by about 74%, 70%, 70%, 80% and 30%, respectively. When L-Arg was combined with L-NNA, the reduction in pancreatic secretion induced by L-NNA was significantly attenuated. SF resulted in a marked rise in plasma insulin and glucagon and this response was completely abolished by L-NNA infusion. Insulin and glucagon levels were 2-3 folds increased by F and L-NNA infusion inhibited these responses while the addition of L-Arg partly reversed this inhibition. Duodenal nutrient produced several fold increase in plasma insulin and glucagon levels that were significantly reduced by L-NNA and this reduction was partially reversed by L-Arg. GRP also caused moderate rise in plasma insulin and glucagon levels which were significantly reduced by L-NNA and this was partially restored by L-Arg. We conclude that SF, F, duodenal nutrient, GRP or urecholine stimulate both the exocrine and endocrine pancreatic secretion and that these effects are mediated, at least in part, through the NO pathway.

1. We investigated the influence of strip length and dorsal or ventral location of rat urinary bladder strips on contractile responsiveness. 2. No differences occurred in the contractile responses of 0.5, 1.0 and 2.0 cm strips to field stimulation, carbachol, ATP, substance P or to KCl when the data were expressed as either absolute tension or as tension per cross-sectional area. However, correction for strip mass resulted in significant decreases in the contractile responses of the 2.0-cm strips compared with the 0.5-cm strips. 3. No differences occurred in length-tension curves for ventral and dorsal bladder strips, even though the strips from the dorsal surface appeared thinner than those from the ventral surface. 4. Strips from the ventral surface exhibited more variability in response to field stimulation and were less sensitive to atropine pre-treatment than were those from the dorsal surface. They were also less sensitive to the contractile effects of carbachol than dorsal strips. Dorsal and ventral strips were equally responsive to ATP, substance P and KCl. 5. Our data indicate that the contractile responsiveness of rat urinary bladder strips is independent of strip length. Although there are some differences between the cholinergic responsiveness of strips from the ventral and dorsal surfaces of the bladder, the differences are so small that for most studies they will probably have no influence on data interpretation.

Previous studies showed that nitric oxide (NO), synthesized from L-arginine (L-arg) by NO synthase (NOS) in vascular epithelium and nerve terminals, affects exocrine pancreatic secretion, but its role in control of endocrine pancreas has not been studied. In this study, the role of NO in the control of pancreatic secretion in response to vagal-cholinergic stimulation and duodenal infusion of nutrients was determined in conscious dogs with chronic pancreatic fistulas. Sham feeding (SF), urecholine iv infusion, and duodenal perfusion with nutrients were used to stimulate the pancreatic protein secretion, and insulin and glucagon release in tests without and with iv infusion of NG-nitro-L-arginine (L-NNA), an inhibitor of NO synthase, L-arg, a substrate of NOS, or their combination was used. SF, urecholine, and duodenal nutrient resulted in the stimulation of pancreatic protein secretion reaching, respectively, 50, 20, and 42% of cerulein maximum. Infusion of L-arg almost doubled the basal protein secretion and tended to increase the secretory response to SF and duodenal nutrient. After infusion of L-NNA, the pancreatic secretory responses to SF, urecholine, and duodenal nutrient were inhibited by about 70, 30, and 75%, respectively. When L-arg was combined with L-NNA, the reduction in pancreatic secretion by L-NNA was significantly attenuated. SF resulted in a significant rise in plasma insulin and glucagon, and this response was completely abolished by L-NNA infusion. Urecholine and duodenal nutrient also resulted in a marked increment in plasma insulin and glucagon, the insulin (but not glucagon) increment being abolished by the pretreatment with L-NNA and reversed by the addition of L-arg.(ABSTRACT TRUNCATED AT 250 WORDS)

The recently synthesized calcitonin gene-related peptide (CGRP) antagonist, human alpha-CGRP 8-37, was used to study its effects on gastric acid secretion. Four dogs with gastric fistula were used to measure the antagonist's physiologic effects in the stomach. All dogs received a bactopeptone dextrose meal (intragastric titration to pH 5.5) with either continuous CGRP 8-37 (1000 pmol/kg/hr) or saline (control). Additionally, intravenous bombesin (75-600 ng/kg/hr) and bethanechol (12.5-100 micrograms/kg/hr) was tested in the presence of the antagonist. Plasma gastrin levels also were measured via radioimmunoassay (RIA) in control and CGRP 8-37-stimulated animals. Gastric acid secretion increased by 100% with infusion of 1000 pmol/kg/hr CGRP 8-37 when compared to the control. Acid output increased 98% with both intravenous antagonist and 600 ng/kg/hr bombesin when compared to bombesin alone. However, no augmentation of acid secretion by CGRP 8-37 was shown with 25 micrograms/kg/hr bethanechol. RIA of plasma gastrin demonstrated no effect with the antagonist when given alone and did not increase bombesin-stimulated gastrin release. We conclude that CGRP 8-37 blocks native CGRP inhibitory effects on gastric acid secretion. Our findings of potentiation of acid secretion by bombesin as well as no change in gastrin levels in the presence of the antagonist is likely due to a blockage in a noncholinergic neuron to the somatostatin cell. Furthermore, CGRP 8-37 did not increase bethanechol-stimulated acid secretion, most likely due to bethanechol's (acetylcholine) nearly ubiquitous positive effects on acid secretion.

The effects of bethanechol in the treatment of dry mouth were assessed in patients with xerostomia after radiation therapy to the head and neck. Bethanechol possesses muscarinic and nicotinic-cholinergic activity that likely accounts for its mode of action. Bethanechol (25 mg, three times daily) was not associated with significant side effects. Statistically significant increases in whole resting saliva (p = 0.003) and whole stimulated saliva (p = 0.001) were seen. In patients with pretreatment stimulated saliva volumes greater than resting saliva volumes, a positive response to subsequent use of the sialagogue was seen.

(R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1H-1,4- benzodiazepin-3-yl]-3-(3-methylphenyl)urea (YM022) is an extremely potent and highly selective gastrin/cholecystokinin (CCK)-B receptor antagonist. We compared the gastrin/CCK-B receptor-blocking properties of this compound with those of the racemate (mixture of YM022 and its S-form), its enantiomer (S-form), L-365, 260 and Cl-988 in vitro and in vivo. YM022 replaced specific binding of [125I]CCK-8 to rat brain gastrin/CCK-B receptors in a stereoselective and competitive manner. The Ki value of YM022 for gastrin/CCK-B receptors in brain were estimated to be 0.068 nM. The racemate, the S-form of YM022, L-365,260 and Cl-988 also replaced gastrin/CCK-B receptor binding, with Ki values of 0.11, 140, 19 and 6.3 nM, respectively. The affinity of YM022 for gastrin/CCK-B receptor was more than 2 orders of magnitude higher than that for rat pancreatic CCK-A receptor and various other receptors, such as benzodiazepine. In vivo, intravenous (i.v.) administration of YM022 inhibited pentagastrin-induced gastric acid secretion in anesthetized rats, with an ED50 value of 0.0078 mumol/kg. Inhibition by the S-form of YM022 was only 33.8% even at the relatively high dose of 1 mumol/kg i.v. L-365,260 (1-10 mumol/kg i.v.) and Cl-988 (0.3-3 mumol/kg i.v.) also antagonized acid secretion induced by pentagastrin, with ED50 values of 4.23 and 1.01 mumol/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

1. The effect of Na+,K(+)-ATPase inhibition by ouabain on gastric acid secretion was studied in the mouse isolated whole stomach preparation. 2. Ouabain caused a transient enhancement of histamine-induced gastric acid secretion followed by an inhibitory phase. On the other hand, ouabain caused a rapid reduction of bethanechol-stimulated acid secretion without an enhancement phase. 3. In dibutyryl cyclic AMP-induced acid secretion, ouabain led to a transient increase in acid secretion followed by a fall, as was seen with the histamine stimulation. Ouabain caused a rapid reduction of A23187-induced acid secretion. 4. Ouabain by itself increased basal acid secretion, and thereafter slowly suppressed the acid secretion. 5. Atropine inhibited both the ouabain-induced enhancement of the stimulated gastric acid secretion and the ouabain-induced stimulation of basal acid secretion. 6. The present study showed that Na+,K(+)-ATPase inhibition by ouabain caused a phasic enhancement of the stimulated gastric acid secretion through release of endogenous acetylcholine when the secretagogues act via an intracellular cyclic AMP pathway. It also inhibited the stimulated acid secretion irrespective of secretagogues, probably through its inhibitory effect on Na+,K(+)-ATPase in the gastric parietal cell.

Objective: The aim was to investigate whether intrinsic cardiac neurones can be involved in the genesis of ventricular arrhythmias., Methods: Nicotinic, muscarinic, beta adrenergic, peptidergic, and amino acidergic agonists, as well as purinergic compounds, were individually administered in microliter quantities adjacent to spontaneously active in situ right atrial neurones in 57 anaesthetised dogs before and after acute decentralisation., Results: Ventricular arrhythmias were induced in one third of the dogs following neurochemical administration. Ventricular arrhythmias are induced much less frequently when intrathoracic extracardiac neurones are modified chemically. Salvos of ventricular premature contractions or ventricular tachycardias were elicited when intrinsic cardiac neurones were modified locally applied nicotine, bethanechol, isoprenaline, angiotensin II, bradykinin, substance P, vasoactive intestinal polypeptide, glutamate, or adenosine. In 60% of those instances in which intrinsic cardiac neuronal activity was modified by a neurochemical, ventricular arrhythmias were elicited. When arrhythmias were induced, activity generated by chemically modified intrinsic cardiac neurones increased from 0.7(SD 0.2) to 2.2(0.4) impulses.s-1 (p < 0.05). Following decentralisation of the intrinsic cardiac nervous system, repeat administration of the same neurochemicals into the same loci elicited ventricular arrhythmias in 42% of those dogs in which ventricular arrhythmias had been elicited previously. Neuronal activity increased [0.8(0.5) to 2.1(0.6) impulses.s-1; p < 0.05] in 86% of these instances., Conclusions: Intrinsic cardiac neurones can be involved in the genesis of ventricular arrhythmias.

The present study compared the contractile and relaxant responses of male and female rabbit bladder neck and urethra to field stimulation (FS) and various contractile and relaxant agents, with special attention paid to the involvement of nitric oxide (NO) in the mediation of field-stimulated relaxation. FS at basal tension elicited a frequency-dependent contractile response in all preparations. The maximal response to high frequency FS was significantly greater in the bladder neck strips isolated from male rabbits than in those from female rabbits. There were no significant differences in the response to bethanechol or phenylephrine between strips isolated from males and females. Field-stimulated responses of the strips from male bladder neck and urethra were greater than the response to phenylephrine. The responses of all strips to FS were greater than those to bethanechol. In addition, the response to phenylephrine was generally greater than that to bethanechol. Phentolamine was a significantly more effective inhibitor of the response of the female bladder neck and urethral strips to FS than of the response of the male strips. The contractile response of all strips to phenylephrine was generally greater than that to bethanechol for both sexes and for both bladder neck and urethral strips. NG-nitro-L-arginine methylester (L-NAME) inhibited totally the field-stimulated relaxation of all strips. Isoproterenol stimulated a slowly developing but significant inhibition of phenylephrine prestimulated contractions. In conclusion, significant differences exist in the magnitude of field-stimulated relaxation between the bladder neck and urethra of both male and female rabbits, and, for all tissues, field-stimulated relaxation could be completely inhibited by pretreatment with L-NAME, an NO synthesis inhibitor.

This initial study correlates the passive length-tension relationship, contractile and relaxant responses to field stimulation and contractile responses to specific autonomic agonists and antagonists with gestational age. Fetal bovine bladders were separated into three groups based on the head-rump length (FL): 30 to 45 cm. (early gestation), 50 to 65 cm. (middle gestation) and 70 to 85 cm. (late gestation). Each bladder was separated into upper and lower bladder segments; longitudinal strips of smooth muscle were isolated and placed in individual muscle baths. Passive length-tension studies demonstrated that compliance was greatest in the bladder of late gestation and lowest in the bladder of early gestation period. Field stimulation (FS) elicited frequency-dependent contractile responses in all strips. In the upper bladder, the maximal response and maximal rate of tension generation to FS was lowest in the youngest fetuses and increased in proportion to the gestational age. In the lower bladders, there were no gestational age-related differences in the maximal response or maximal rate of tension generation in response to field stimulation. The maximal response of the upper bladder to bethanechol increased significantly from the youngest gestational age to mid-gestation, with no further changes between mid- and late gestation. The maximal response to field stimulation and bethanechol were equal between upper and lower bladder segments for the youngest gestational bladders, whereas for the oldest gestational ages, the maximal response of the upper bladder to FS and bethanechol were significantly greater than the responses of the lower bladder. In the presence of maximal precontraction with bethanechol, FS induced a rapid and marked decrease in tension. The magnitude of the relaxation was substantially greater for the strips of lower bladder than for the strips of upper bladder at late gestation. In lower bladders, the magnitude of the field stimulated relaxation was greater in the strips from the older fetuses than in the strips from younger fetuses. In all strips, field stimulated relaxations were completely inhibited by pretreatment with L-NAME (an inhibitor of nitric oxide synthesis), indicating that the FS-induced relaxation was due to nitric oxide. In addition to nitric oxide-induced relaxation, beta adrenergic stimulation also induced a significant relaxation of the isolated strips. In summary, these data suggest that, in the tubular shaped fetal bovine bladder, there were distinct differences in the autonomic responses between the upper bladder segment and the lower bladder segment in the late gestation period.

Parotid salivation was stimulated by infusion of bethanechol chloride into anaesthetized brushtail possums to ascertain maximal flow rates, salivary composition and dietary adaptations of salivary function. Secretion rates for one gland ranged from 5.3 +/- 0.16 to 84.3 +/- 3.20 microliters/min (2.4 +/- 0.07 to 37.8 +/- 1.43 microliters/min per kg body weight). Salivary osmolality (160.8 +/- 15.39 to 248.2 +/- 8.70 mosmol/kg) and the concentrations of Na (63.1 +/- 10.93 to 124.1 +/- 5.52 mmol/l) and HCO3 (19.5 +/- 3.41 to 89.0 +/- 3.19 mmol/l) were positively correlated with flow rate. The concentrations of urea (7.8 +/- 0.64 to 4.6 +/- 0.33 mmol/l), PO4 (2.6 +/- 0.25 to 0.96 +/- 0.10 mmol/l), H+ (46.2 +/- 16.30 to 9.0 +/- 1.51 nequiv/l), K (21.4 +/- 3.73 to 13.7 +/- 2.33 mmol/l), Ca (3.7 +/- 0.53 to 2.2 +/- 0.27 mmol/l) and Mg (0.3 +/- 0.07 to 0.04 +/- 0.007 mmol/l) fell with increasing flow rate. The relations between flow rate and amylase activity (22.6 +/- 10.47 to 10.5 +/- 3.68 mu kat/l), protein concentration (2.7 +/- 0.61 to 1.3 +/- 0.28 g/l), and Cl concentration (62.1 +/- 6.88 to 50.6 +/- 6.37 mmol/l) were inconsistent between experiments. Salivary Na/K ratios were not decreased by infusion of aldosterone (2.2-22.2 nmol/h for 5 h), showing that the gland of Na-replete possums is unresponsive to short-term increases in mineralocorticoids. The low salivary amylase activity, less than that of kangaroos, presumably reflects the interaction of evolutionary history of the possum with its natural low-starch diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholinergic pathways in the central nervous system positively influence growth hormone (GH) secretion. In fact pyridostigmine, a cholinesterase inhibitor, enhances both basal and GH-releasing hormone (GHRH)-induced GH secretion while, conversely, pirenzepine, an antagonist of muscarinic M1 receptors, inhibits the GH response to GHRH and to other physiological and pharmacological stimuli. The effect of the cholinergic system on GH secretion probably takes place via inhibition of the release of endogenous somatostatin. In this study in 36 normal adults (26 males and 10 females, age 22-35 years) we compared the effects of three cholinesterase inhibitors (pyridostigmine, 120 mg p.o., n = 19; neostigmine, 10 micrograms/kg i.v., n = 6; physostigmine, 12.5 micrograms/kg i.v., n = 6) and bethanechol, a direct muscarinic receptor agonist that is mainly active on muscarinic M3 receptors (25 micrograms/kg i.v., n = 5), on both basal and GHRH (1 microgram/kg i.v.)-stimulated GH secretion. Pyridostigmine, neostigmine and physostigmine induced a significant GH increase (peak vs. basal levels, mean +/- S.E.: 10.4 +/- 1.6 vs. 0.6 +/- 0.2 micrograms/l, P = 0.0001; 13.3 +/- 1.2 vs. 0.5 +/- 1.1 micrograms/l, P = 0.004; and 14.9 +/- 3.1 vs. 2.7 +/- 1.1 micrograms/l, P = 0.025;, respectively). These drugs also induced a similar potentiation of the GH response to GHRH (peak: 48.3 +/- 5.6 vs. 16.2 +/- 2.2 micrograms/l, P = 0.0001; 49.2 +/- 2.2 vs. 19.9 +/- 5.1 micrograms/l, P = 0.006; and 76.9 +/- 12.4 vs. 18.1 +/- 5.3 micrograms/l, P = 0.001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of parasympathetic neurotransmission in regulating periorbital smooth muscle function was investigated in urethane-anesthetized rats. Parasympathetic nerves were activated by stereotaxic electrical stimulation (20 Hz, < or = 2.0 V) of the ipsilateral superior salivatory nucleus, which gives rise to preganglionic innervation to the pterygopalatine ganglion and hence to the orbital targets. This approach permits selective parasympathetic activation that cannot be attained at more peripheral sites. Target responses were measured by recording changes in tarsal smooth muscle tension from the superior eyelid. Parasympathetic stimulation caused a small decrease in resting tension (-73 +/- 4 mg) that was not altered when the muscle was partially contracted with methoxamine. However, adrenoceptor-mediated contraction induced by cervical sympathetic nerve stimulation was attenuated in a frequency-dependent manner, with inhibition greatest at higher sympathetic stimulation frequencies (-338 +/- 35 mg at 8 Hz). This attenuation was blocked by the muscarinic receptor antagonist atropine methyl nitrate. Administration of the muscarinic agonist bethanechol increased resting tarsal muscle tension (655 +/- 34 mg). However, sympathetically mediated contraction at 2 Hz (1295 +/- 53 mg) was decreased by bethanechol administration to a value (710 +/- 37 mg) not significantly different from the contraction caused by bethanechol alone. We conclude that muscarinic receptors are present on tarsal smooth muscle, where they elicit contractions, and on sympathetic nerves, where they inhibit neurotransmission presumably by depressing noradrenaline release.(ABSTRACT TRUNCATED AT 250 WORDS)

An important function of cholinergic projections to the cerebellar cortex may be to modulate the effects of classical afferent inputs to the cerebellar cortex. This hypothesis is supported by the recent observation that cholinergic agonists act at muscarinic receptors in the cerebellar cortex to facilitate Purkinje cell responses to glutamate, the excitatory neurotransmitter of parallel fibers [Brain Res., 617 (1993) 28-36]. Since Purkinje cell excitability is influenced by inhibitory input from basket and stellate cells as well as by excitatory input from granule cells and climbing fibers, the present study investigated whether muscarinic agonists could also modify the Purkinje cell responses to GABA, the putative inhibitory transmitter of basket and stellate neurons. In anesthetized rats, microiontophoretic application of bethanechol produced a long-lasting enhancement of GABA-evoked inhibition of firing of Purkinje cells in the cerebellar vermis (22/25 cells) regardless of whether bethanechol increased, decreased or failed to alter the basal firing rate of the cell. The muscarinic antagonist scopolamine prevented the bethanechol-induced increase in the GABA response. It appears, therefore, that cholinergic activation of muscarinic receptors enhances not only the excitatory but also the inhibitory component of cerebellar cortex circuitry. Further experiments are required to investigate whether this combination of effects may potentiate the signal processing capabilities of the cerebellar cortex.

In a preliminary study we showed that 14 days of furosemide infusion in rabbits caused increases in bladder mass and contractile responses of bladder body strips to field stimulation, bethanechol, ATP and KCl. The present study investigated the temporal effects of furosemide-induced diuresis on micturition, bladder mass, bladder wall proliferation activity and DNA synthesis. In addition, contractile responses of bladder body strips were monitored. Furosemide-containing osmotic pumps were implanted in male New Zealand White rabbits. Micturition was monitored for 7 days. Biochemical analyses were done 3, 7 and 14 days after implantation. Contractile responses were measured at 3 and 7 days. Polyuria and polydipsia started within 1 day after implantation of furosemide-containing osmotic pumps and continued at the same level for 7 days. Bladder mass was significantly increased at 3 and 7 days. Diuresis stimulated 3H-thymidine uptake and caused an increase in bladder DNA concentration at 3 days. However, both DNA concentrations and 3H-thymidine levels returned to control levels by 7 days. Contractile responses to field stimulation and agonists were increased at 7 days but unchanged at 3 days. The data confirm that modest increases in bladder mass and the ensuing increases in contractile function are a normal and beneficial physiological response to diuresis.

Effects of the following treatments on abomasal and duodenal myoelectric activity in yearling cattle were studied: 2 ml of 0.9% sodium chloride solution (NACL); 0.07 mg of bethanechol (BET)/kg of body weight; 0.1 mg of metoclopramide (MET)/kg; and 0.07 mg of bethanechol and 0.1 mg of metoclopramide (BETMET)/kg. All treatments were administered SC during the early part of phase I of the migrating myoelectric complex. Myoelectric signals were recorded for 4 hours after administration of the treatments from 1 electrode in the antrum and 3 electrodes in the duodenum. For the antral spike rate (ASR), there was no significant difference among treatments during the first hour, but the ASR was significantly (P < 0.05) greater during hours 2 to 4 after treatment with BETMET, compared with ASR for MET alone. The duodenal spike rate (DSR) was significantly (P < 0.05) greater during the first hour after administration of BETMET than after the other treatments. After administration of BET, DSR was significantly (P < 0.05) greater than after MET or NACL. There was no difference in DSR after MET, compared with DSR after NACL. There was no significant difference in DSR among treatments during the second and third hours. The total antegrade propagating spike (TAPS) count was greater after administration of BETMET in all hours, compared with the other treatments. The ratio of TAPS to total spikes on the orad-most duodenal electrode was significantly (P < 0.05) greater after BETMET during hours 1 and 2.

In the paper the influence of ambroxol, betanechol and mesna on the production of tear fluid by the lacrimal gland in rabbits was studied and compared with the effectiveness of bromhexine hydrochloride. Tear secretion was stimulated by the Schirmer I and lysozyme tests. The obtained results indicate that all four examined drugs stimulate the production of tear fluid. The greatest stimulation of secretion was observed after mesna and then after betanechol and ambroxol. The least potent drug was bromhexine.

Estrogens have been postulated to play an important role in modulation of vascular responses to endogenous reactive substances. The effects of chronic in vivo treatment with 17 beta-estradiol on relaxant responses to acetylcholine were investigated in the rat aorta isolated from prepubertal female rats. The selectivity of effects of 17 beta-estradiol on acetylcholine-induced relaxation was evaluated using histamine, another endothelium-dependent relaxant in the rat aorta. 17 beta-Estradiol significantly enhanced endothelium-dependent relaxation induced by acetylcholine, but did not alter the vascular responses to acetylcholine in endothelium-denuded aortic rings isolated from prepubertal female rats. In contrast, 17 beta-estradiol did not change endothelium-dependent relaxation induced by histamine in endothelium-intact aortic rings. The results of the present study demonstrate that 17 beta-estradiol selectively enhances acetylcholine-induced endothelium-dependent relaxation in the rat aorta.

The effects of nebracetam (4-aminomethyl-1-benzylpyrrolidine-2-one hemifumarate, WEB 1881FU), a potential cognitive enhancer, on acetylcholine release from the preganglionic nerve terminals were investigated in the isolated dog stellate ganglia. Acetylcholine release from the isolated ganglia by preganglionic stimulation (5 Hz) was enhanced in the presence of nebracetam, 10(-7) to 10(-5) M. The release was decreased to a certain extent by bethanechol, 10(-5) M, and this decrease was completely antagonized by AFDX-116 (10(-5) M), a selective M2 muscarinic antagonist, but was unaffected by nebracetam (10(-6) M). Under the depleted condition of acetylcholine induced by pretreatment with hemicholinium-3 (10(-5) M) in combination with prolonged preganglionic stimulation, the release was increased to a degree by nebracetam or choline alone and was markedly increased in the presence of both nebracetam and choline. Nebracetam did not directly act on choline acetyltransferase activity, but acetylcholine formation was stimulated in the isolated ganglion incubated with the agent at 10(-6) M and in the ganglion isolated from the dog to which nebracetam, 5 mg/kg, was previously administered i.v. Uptake of choline in the isolated ganglia was not altered by nebracetam (10(-6) M) but was enhanced under the depleted conditions. These findings suggest that nebracetam enhances acetylcholine release from presynaptic sites of dog stellate ganglia not by blocking presynaptic M2 muscarinic autoreceptors but by accelerating acetylcholine formation, and by increasing choline uptake when acetylcholine is depleted.

A parotid acinar degranulation of approximately 60 and 40% was observed in cats under pentobarbitone anaesthesia after a 90-min period of continuous stimulation of the parasympathetic auriculo-temporal nerve at 10 Hz in the absence and presence of atropine, respectively. Atropine completely abolished the large fluid response of the gland to the nerve stimulation. In the non-atropinized cats, bethanechol, infused into the carotid artery at a dose rate evoking a salivary flow similar to that in response to parasympathetic nerve stimulation, caused an acinar degranulation of approximately 25% and acinar vacuolation. Vasoactive intestinal peptide (VIP; 0.5 microgram kg-1 min-1 also infused into the carotid artery for 90 min) caused an acinar degranulation of the same magnitude as the parasympathomimetic drug but the peptide did not give rise to any fluid secretion or vacuole formation. The experiments were performed in the presence of alpha- and beta-adrenoceptor blockers. Thus, in parotid glands of the cat, producing no overt secretion of fluid, non-adrenergic, non-cholinergic (NANC) mechanisms may be at work causing exocytosis of the acinar granules. These mechanisms are also likely to contribute to the secretion of granules in response to parasympathetic nerve activity in the absence of blockade of the classical autonomic receptors.

Urinary bladder dysfunction was investigated in spontaneously diabetic Chinese hamsters of the Asahikawa colony (CHAD). The wet weight of the urinary bladder was significantly increased in CHAD when compared with non-diabetic controls. In response to continuous infusion of physiological saline into the bladder under anesthesia, regular micturition was observed in controls. However, the threshold volume (i.e. the minimum volume at which rhythmic contraction appeared) was significantly increased and the amplitude of bladder contractions during micturition was decreased in CHAD aged 3-5 months (duration of diabetes, 0.6-2.2 months), leading to incomplete micturition. The frequency of micturition was also increased. Overflow incontinence was observed in all CHAD aged 13-15 months (duration of diabetes, 10-14 months). Acetylcholinesterase staining and activity in the urinary bladder walls were both significantly decreased in CHAD compared with controls. The in vitro increment of urinary bladder pressure caused by stimulation with bethanechol was not different between CHAD and controls. These findings suggest that CHAD have urinary bladder dysfunction which is caused by autonomic neuropathy and not by detrusor myopathy.

In the paper the influence of ambroxol, bethanechol, mesna and bromhexine hydrochloride on the morphologic appearance of the lacrimal glands in rabbits was studied with the use of light and transmission electron microscopy. The examination of the lacrimal glands in light microscopy has shown in comparison with the control group an increase in the number of secretory granules in rabbit glands after treatment with different drugs. In electron microscopy in animals, after treatment, much more prominent rough endoplasmic reticulum with a considerable distention of the cisternae and increase of the number of secretory granules in the cytoplasm of the cells were seen. The greatest stimulation of the production of tear fluid was observed after treatment with mesna. Nearly similar results were obtained after bethanechol and slightly worse after ambroxol. The least potent drug was bromhexine.

Exogenous eicosanoids were reported to affect pancreatic secretion, but it is unknown whether this effects is mediated by the changes in pancreatic circulation or by direct action on pancreatic secretory cells. In this study the effects of prostaglandins (PG), leukotriene C4 (LTC4) and platelet activating factor (PAF) and the blockers of their biosynthesis or receptor antagonists on amylase release from the isolated rat pancreatic acini were examined. The acini were incubated with pancreatic secretagogues, such as caerulein or urecholine in the presence or absence of various concentrations (10(-9)-10(-5) M) of PGE2, Nocloprost (stable analog of PGE2), PGI2, PGF1 alpha, LTC4, PAF, indomethacin (inhibitor of endogenous PG formation) and A-63162 (blocker of endogenous LT biosynthesis). PGE2, PGI2 and PGF1 alpha inhibited secretagogues-stimulated enzyme secretion from isolated pancreatic acini but their inhibitory potency was about 1000 times lower, on molar basis, than that of Nocloprost. PAF and LTC4 produced concentration-dependent stimulation of amylase release from the unstimulated acini reaching about 50% of caerulein-induced maximal response and enhanced amylase release induced by caerulein or urecholine. The effects of PAF and LTC4 were reversed by the addition of respective receptor antagonist for PAF (TCV-309) and for LTC4 (FPL-55712). These results indicate that PG inhibit, while PAF and LTC4 stimulate pancreatic enzyme secretion and thus could be implicated in the control of this secretion.

Previous studies have shown that a brief rise in plasma insulin followed by a transient fall and rise in blood glucose precede the initiation of feeding in nondeprived rats. In this study, a cholinergic agonist, bethanechol chloride, which is known to induce a brief spike in plasma insulin, was infused intravenously in an attempt to induce transient declines in blood glucose and meal initiation in free-feeding rats. When the blood glucose response to bethanechol chloride administration met the criteria for a transient decline in blood glucose, meal initiation occurred within 20 min in nine out of ten trials. However, if the blood glucose response to bethanechol chloride administration failed to meet the criteria for a transient decline in blood glucose, meal initiation did not occur. The frequency of successful induction of feeding was higher in the late light cycle (80%) compared with the early light cycle (14%) of the photoperiod. These results suggest that cholinergic stimulation can induce feeding only after a brief fall and rise in blood glucose. The blood glucose and behavioral responses to the cholinergic stimulus appear to be strongly dependent on the metabolic state of the animal. These results further strengthen the evidence for a causal relationship between transient declines in blood glucose and meal initiation in free-feeding rats.

Muscarinic receptor agonist and antagonist effects on acetylcholine release evoked by electrical or dimethylphenylpiperazinium stimulation from guinea pig ileum were evaluated by measuring acetylcholine with a high performance liquid chromatography-electrochemical detector system. AF102B (cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine), a muscarinic M1 receptor agonist, increased markedly the evoked release of acetylcholine. In contrast, pirenzepine decreased the evoked acetylcholine release. 4-DAMP (4-diphenyl-acetoxy-N-methylpiperidine methiodide) and p-F-HHSiD (p-fluoro-hexahydrosiladifenidol), muscarinic M3 antagonists, increased the release of acetylcholine. Atropine enhanced acetylcholine release to a similar extent while bethanechol reduced the electrically evoked acetylcholine release. This reduction was virtually unaffected by methoctramine, but was antagonized by 4-DAMP or p-F-HHSiD. The results from direct determination of acetylcholine suggest that, in contrast to autoinhibition by stimulation of muscarinic M3 receptors, stimulation of presynaptic muscarinic M1 receptors is predominantly involved in enhancement of the acetylcholine release from guinea pig ileal nerves, and that AF102B functions as a muscarinic M1 agonist in this peripheral neuron.

We evaluated the change in density of total senile plaques, plaque subtypes, and neurofibrillary tangles, from biopsy to autopsy in left frontal cortical sections from four patients with clinically typical Alzheimer's disease (AD). Comparisons were made on sections stained with modified Bielschowsky and Thioflavin S. In two cases, comparisons were also made on tissue stained with a monoclonal Alz-50 antibody and an antiserum to A beta (beta-amyloid protein). Despite a marked decline in mental status over several years of follow-up clinical evaluations, there was no consistent significant change in numerical density of plaques or tangles among the four cases. However, we did find fewer primitive plaques in the autopsy specimens. These results from longitudinally evaluated persons with typical AD suggest that although plaques and tangles may serve as adequate markers of the presence of AD, their numerical density within a single neocortical region may not reflect dementia severity. This conclusion supports the results of recent cross-sectional studies on the progression of pathology among persons with AD.

Background: Delayed gastric emptying has been reported during pregnancy; however, its underlying mechanism is poorly understood. The purpose of this study was to determine if electromechanical activity of antral circular muscle is decreased during pregnancy., Methods: Antral muscle strips from third-trimester pregnant and age-matched control virgin female guinea pigs were studied in vitro., Results: Spontaneous and bethanechol-induced phasic antral contractions from pregnant guinea pigs were reduced significantly in force compared with control virgin animals. Although the resting membrane potentials were similar, the electric slow waves of pregnant animals displayed significant decreases in upstroke amplitude, plateau amplitude, and number of spikes during the plateau potential compared with control animals. The voltage-tension relationship was similar in pregnant and control animals., Conclusions: This study indicates that (1) the force of antral circular muscle contractions is decreased during pregnancy and (2) this decreased force is secondary to a diminished slow wave depolarization. The results suggest that a change in electromechanical activity of gastric muscle is a cause of altered gastric motility in pregnancy.

Insulin secretion was evaluated in response to the muscarinic agonist, bethanechol, and to the antagonist, atropine, in three-month-old female homozygous lean (Fa/Fa) and obese (fa/fa) Zucker rats, using an in vitro pancreas perfusion. Three doses of bethanechol were used (0.5, 5 or 50 microM). Bethanechol at 50 microM concentration had a significant potentiating effect on glucose-induced insulin secretion in pancreata from both lean and obese rats. There was no effect of atropine (25 microM) on insulin secretion in pancreata from either lean or obese rats. In another study, the perfusate used contained glucose at 75, 125 or 200 mg/dl for the entire 60 min period. Perfusate, with or without bethanechol (50 microM), was infused from 21-40 min, using a side-arm syringe. In general, bethanechol significantly increased insulin secretory rates in both lean and obese rats. Since the pancreas of obese rats secretes more insulin to the same glucose concentration than the pancreas of lean rats, we compared changes in insulin release due to bethanechol in obese and lean rats having comparable basal insulin secretory rates during the 11-20 min period. To produce comparable insulin secretion, glucose levels in the perfusate were kept lower in the obese group (75 mg/dl). In the comparably secreting lean group, a glucose level of 200 mg/dl was required. We also compared changes in insulin secretory rate due to bethanechol stimulation between groups with comparable insulin secretory rates during the 21-40 min period in the control groups, i.e. 75 mg/dl glucose in the obese group vs. 125 mg/dl glucose in the lean group.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomus cells of rat carotid bodies can be electrotonically coupled. This was determined by simultaneous intracellular recording and stimulation of two neighboring cells. Voltage applied into one cell (V1), was detected in the other cell as E2. The ratio E2/V1 or coupling coefficient (KC), varied from 0.003 to 1. R0 or input resistance (24.1-3,500 M omega), was calculated from the voltage elicited in the injected cell by current injection (V1/I1). The coupling resistance (RC) was estimated by using Bennett's model and was inversely related to KC. It ranged from 8.5 to 46,112 M omega. Values for KC are provisional since we may not have always recorded from immediately adjacent cells. Similarly, calculations of R0 and RC may not be accurate since, in all probability, there is a multicellular network. Stimulation by hypoxia (100% N2 or Na2S2O4), acidity (lactic acid or 100% CO2), dopamine, ACh, nicotine and bethanechol depolarized the majority of glomus cells, their input resistance decreased and cells became uncoupled. Fewer cells were either unaffected or coupling increased. There was a significant and negative correlation between changes in coupling coefficient and in coupling resistance.

Partial outlet obstruction is one of the major urological complications induced by benign prostatic hypertrophy (BPH). The current study describes the time course of the effect of mild partial outlet obstruction (in rats) on in vivo micturition parameters, DNA synthesis, and on the in vitro response of the bladder to field stimulation, bethanechol, methoxamine, ATP, and KCl. Mild partial outflow obstruction was created by placing a catheter (outside diameter: 1.70 mm.) transabdominally in front of the urethra, tying a ligature (2-zero silk) around both the urethra and catheter, and then removing the catheter. The micturition pattern was monitored for 2 days prior to surgery, and then continuously for 14 days following the surgery. The changes in bladder weight and the in vitro detrusor function of control (sham operated) and obstructed bladders (1, 3, 5, 7, 14 and 28 days after surgery) were examined. Micturition frequency in the dark cycle decreased immediately after the operation, and then increased linearly reaching a maximum at the 5th day, and stabilized at this increased level for the duration of the micturition study. The frequency of the dark cycle was also decreased immediately after the sham surgery and then gradually increased over the period of observation. Bladder weight increased by day 1 following surgery, and remained high throughout the 28 day study. The contractile response of the obstructed bladder base to field stimulation was reduced at days 1 and 3. The response then increased above control for day 5, reached a maximum response at day 7 and remained at this level for days 14 and 28. A similar pattern was observed for the contractile response of the bladder body to bethanechol and KCl, and for the bladder base to methoxamine and KCl. Both obstructed and sham surgeries increased bladder DNA content and 3H-thymidine incorporation, which reached maximal values on days 5 and 3, respectively. DNA content and 3H-thymidine incorporation of obstructed bladders were greater than those of sham operated bladders. In conclusion, partial outlet obstruction in the rat resulted in a progressive increase in bladder mass, an increase in micturition frequency, increases in the in vitro contractile response to field stimulation, bethanechol, methoxamine, and KCl, and increases in bladder DNA content and 3H-thymidine incorporation.

Background: Somatostatin inhibits pancreatic exocrine secretion in intact animals but not in vitro, suggesting an indirect effect. The present study examined the influence of extrapancreatic nerves and intrapancreatic cholinergic activity on somatostatin-induced inhibition of pancreatic exocrine secretion in conscious dogs., Methods: Seven dogs underwent extrapancreatic denervation and creation of pancreatic fistulae, while a second group of 6 dogs had pancreatic fistulae created without denervation. The pancreatic responses to graded doses of secretin (16-500 ng.kg-1.h-1), both alone and during background infusions of somatostatin-14 (400 and 800 pmol/L.kg-1.hr-1), were determined in all dogs. The secretin dose response was then repeated with a continuous infusion of bethanechol (90 micrograms.kg-1.h-1) both with and without somatostatin-14 (800 pmol/L.kg-1.h-1)., Results: Secretin-induced bicarbonate and protein outputs were significantly inhibited by somatostatin-14 in both the innervated and denervated animals. The inhibitory effects of somatostatin-14 were partially reversed by bethanechol in the innervated animals and completely reversed in the denervated animals. Bethanechol alone potentiated secretin-induced bicarbonate output from both the innervated and denervated pancreas., Conclusions: The data suggest that extrapancreatic nerves do not mediate the inhibitory effects of somatostatin-14. Rather, somatostatin-14 appears to inhibit secretin-induced pancreatic response by an intrapancreatic cholinergic mechanism.

The mechanisms and site of action of somatostatin-induced inhibition of pancreatic enzyme secretion were investigated using different stimulants of pancreatic secretion acting on different sites in anesthetized rats. Administration of graded doses of somatostatin-14 resulted in a dose-related inhibition of pancreatic protein secretion evoked by 2-deoxy-D-glucose, a central vagal stimulant that acts by stimulating the dorsal vagal nuclei. The lowest effective dose of somatostatin-14 was 1.0 microgram.kg-1 x h-1; maximal effective dose was 25 micrograms.kg-1 x h-1, which resulted in complete inhibition of protein output. Similarly, somatostatin-14 at a dose of 25 micrograms.kg-1 x h-1 also completely inhibited pancreatic protein secretion in response to a physiological concentration of cholecystokinin octapeptide (CCK-8), which acts via a vagal afferent pathway. In contrast, pancreatic protein outputs evoked by bethanechol, which directly stimulates pancreatic muscarinic receptors, or electrical stimulation of the vagal trunk, which activates the vagal efferent pathway, were unaffected by somatostatin-14. In separate studies, we demonstrated that perivagal treatment with the sensory neurotoxin capsaicin impaired pancreatic responses to CCK-8 but had no effect on the inhibitory action of somatostatin-14 on pancreatic secretion evoked by 2-deoxy-D-glucose, ruling out an effect of somatostatin on the vagal afferent pathway. Similarly we also demonstrated that perineural capsaicin treatment of the celiac-superior mesenteric ganglia did not affect the inhibitory action of somatostatin. These findings indicate that somatostatin inhibits 2-deoxy-D-glucose- and CCK-8-evoked pancreatic enzyme secretion via a vagal pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

The cerebellar cortex contains diffusely distributed cholinergic fibers and both muscarinic and nicotinic receptors. Behavioral studies suggest that an important function of this cholinergic innervation may be to modulate the effects of afferent input to the cerebellar cortex. The present study compared the effects of the muscarinic agonist bethanechol on basal firing rates and on glutamate-evoked firing of Purkinje cells in the vermis of the cerebellum of anesthetized rats. Microiontophoretic application of bethanechol produced a slowly developing, long-lasting enhancement of glutamate-evoked firing which was often disassociated from the bethanechol effect on the basal firing rate. Bethanechol increased the glutamate response of 22/33 Purkinje cells regardless of whether bethanechol increased, decreased or failed to alter the basal firing rate of the cell. The muscarinic antagonist scopolamine prevented the bethanechol-induced increase in the glutamate response. For 7/33 Purkinje cells, bethanechol decreased the glutamate-evoked response. However, this decrease did not appear to be mediated by muscarinic receptors because it was not blocked by scopolamine and it was mimicked by application of the vehicle alone. Acetylcholine application produced a long-lasting increase in the glutamate response of 4/5 Purkinje cells that was similar to the bethanechol effect. These data indicate that the cerebellar cholinergic system exerts a prominent modulatory influence on Purkinje cell excitability by acting through muscarinic receptors.

The morphology and contractile function of the urinary bladder can be significantly altered in response to specific forms of physiological and pathophysiological stress placed upon it. For example, partial outlet obstruction results in a marked increase in bladder mass (weight) with associated alterations in the contractile response to specific forms of stimulation. Diabetes and its associated diuresis also induce significant alterations in bladder weight and contractile function. The current study was designed to determine if the increase in bladder weight induced by diuresis is associated with contractile alterations similar to those observed following partial outlet obstruction. Diuresis was induced by continual slow-infusion of furosemide using osmotic pumps. The results can be summarized as follows: 1) After two weeks of furosemide treatment the bladder mass was significantly greater than in the controls. 2) Furosemide-treated rabbits consumed and excreted three times more fluid than did the controls. 3) In vivo cystometric capacity and bladder compliance of the furosemide-treated rabbits were significantly increased. 4) Diuresis induced a significant increase in the contractile response of isolated bladder body strips to field stimulation, ATP, bethanechol, and KCl. 5) Furosemide treatment had no effects on the contractile responses of bladder base strips to any form of stimulation. Diuresis resulted in a significant increase in bladder weight and an associated increase in the contractile state of the bladder body, presumably through an increase in smooth muscle.

Background: Recently, calcitonin gene-related peptide (CGRP) receptors have been identified in the central nervous system. Therefore whether CGRP inhibits pancreatic enzyme secretion at a central site was investigated., Methods: In vivo studies were performed on rats to examine the effect of CGRP on pancreatic enzyme secretion evoked by stimulants that act on different sites: (1) 2-Deoxy-D-glucose (2DG), a central vagal stimulant; (2) cholecystokinin, which acts via vagal afferent pathways under physiologic conditions; (3) electric vagal nerve stimulation, which stimulates vagal release of acetylcholine in the pancreas; and (4) bethanechol, which directly activates pancreatic muscarinic receptors., Results: CGRP produced a dose related inhibition of pancreatic secretion evoked by 2DG. Complete inhibition was observed at a dose of 25 micrograms.kg-1 x h-1. Similarly, CGRP at a dose of 50 micrograms.kg-1 x h-1 completely inhibited pancreatic protein secretion in response to a physiological concentration of cholecystokinin octapeptide (CCK-8). In contrast, pancreatic protein secretion evoked by bethanechol or electrical stimulation of the vagal trunk were unaffected by CGRP. It was also shown that perivagal capsaicin treatment impaired pancreatic responses to CCK-8 but not to 2DG ruling out an effect of CGRP on vagal afferent pathway., Conclusions: Our data indicates that CGRP inhibits pancreatic enzyme secretion evoked by 2DG or CCK-8 via vagal pathways. CGRP exerts its inhibitory action at a central vagal site.

To establish the mechanism(s) and site(s) of action of cholecystokinin (CCK) on pancreatic secretion under physiological conditions, we used an in vivo model using anesthetized rats with pancreaticobiliary cannulas. Infusion of CCK-8 (10-160 pmol/kg per h) produced a dose-dependent increase in plasma CCK levels. CCK-8 infusion at 40 pmol/kg per h produced a plasma CCK level of 7.9 +/- 1.5 pM and an 80% increase in pancreatic protein output over basal. This level was closely approximated by a postprandial peak plasma CCK level by 6.2 +/- 1.1 pM. Pretreatment with atropine or hexamethonium completely abolished pancreatic protein response to low doses of CCK-8 (10-40 pmol/kg per h) but had only partial effect on doses > 40 pmol/kg per h. Bilateral vagotomy also abolished the pancreatic responses to low doses of CCK-8. Similarly perivagal treatment with a sensory neurotoxin, capsaicin, caused a complete inhibition of pancreatic protein secretion in response to CCK-8 infusion. In contrast, pancreatic protein responses to bethanechol were similar in control and capsaicin-treated rats. In separate studies we demonstrated that gastroduodenal but not jejunal application of capsaicin for 30 min abolished pancreatic protein secretion in response to physiological doses of CCK-8. In conclusion, CCK at physiological levels stimulates pancreatic enzyme secretion via a capsaicin-sensitive afferent vagal pathway originating from the gastroduodenal mucosa.

The influence of extrapancreatic nerves and intrapancreatic cholinergic activity on the inhibition of pancreatic exocrine secretion by peptide YY (PYY) was studied in conscious dogs. Chronic pancreatic fistulae were created in five mongrel dogs while a second group of five dogs also underwent complete pancreatic denervation. After recovery, a continuous infusion of secretin (62 ng/kg/hr) and cholecystokinin (50 ng/kg/hr) was administered over 2 hr. An infusion of PYY (400 pm/kg/hr) was then given randomly, during either the first or second experimental hour. The experiments were then replicated with a continuous background infusion of (90 micrograms/kg/hr) bethanechol, a cholinergic agonist. The secretin/cholecystokinin-induced bicarbonate and protein outputs were significantly inhibited by PYY in both the innervated and denervated animals. In the denervated animals, bethanechol eliminated the inhibitory effects of PYY. We conclude that extrapancreatic nerves do not mediate the inhibitory effects of PYY. The results suggest that PYY inhibits secretin/cholecystokinin-induced pancreatic response by an intrapancreatic cholinergic mechanism.

Background: Simultaneous and spontaneous contractions are frequently recorded in patients with esophageal motility disorders. The aim was to investigate the pathogenesis of swallow-induced simultaneous and spontaneous contractions., Methods: The pathogenesis was studied in patients with normal peristaltic contractions (control group) and in patients with functional dysphagia with either simultaneous contractions (group A), with peristaltic but prolonged contractions (group B), and with frequent spontaneous contractions (group C)., Results: Simultaneous contractions had latencies of 2.9 +/- 0.2 seconds compared with 6.4 +/- 0.2 seconds for normal peristaltic contractions and 5.8 +/- 0.4 seconds for prolonged peristaltic contractions. Paired swallows at intervals of 5 seconds generated one peristaltic sequence after the second swallow in subjects with normal peristalsis and two sets of contractions in patients with simultaneous contractions. Ten consecutive swallows taken at 5-second intervals inhibited the spontaneous contractions evoked by bethanechol in control subjects but had no significant effect on the spontaneous contractions of subjects with simultaneous contractions. Atropine reduced the frequency, force, and duration of the spontaneously generated contractions in group C., Conclusions: The shorter latency of simultaneous contractions may be caused by a defective deglutitive inhibitory reflex, and spontaneous contractions appear to be generated by swallow independent discharges of acetylcholine.

Nitric oxide (NO) synthesised from L-arginine is an intercellular messenger in various biological actions including endothelial dependent relaxation and inhibition of platelet aggregation. This study explored the role of the L-arginine-NO pathway in the regulation of gall bladder motility. Intraluminal gall bladder pressure was recorded in anaesthetised guinea pigs in response to cholecystokinin or bethanechol before and after treatment with specific NO synthase inhibitors (NG-nitro-L-arginine, NG-nitro-L-arginine methyl ester, or NG-monomethyl-L-arginine), or with an NO donor (sodium nitroprusside). Baseline gall bladder pressure significantly increased after treatment with the NO synthase inhibitors. Responses to cholecystokinin (0.025-1.25 nmol/kg) were significantly enhanced after treatment with NG-nitro-L-arginine methyl ester and lasted two to threefold longer than in control experiments. The effect of the inhibitor both on resting pressure and on cholecystokinin induced changes was reversed by L-arginine but not by D-arginine. Pretreatment with the inhibitors also induced a significant enhancement of the response to bethanechol. On the other hand, sodium nitroprusside abolished the response to low dose cholecystokinin and reduced the response to a high dose by about 80%. In vitro experiments with isolated gall bladder strips showed a significant enhancement of the contractile response to cholecystokinin or bethanechol after preincubation with the NO synthase inhibitor. Calcium dependent activity of NO synthase was detected in fresh homogenates from gall bladder tissue and incubation with endotoxin induced considerable calcium independent activity. These findings support the existence of a key L-arginine-nitric oxide pathway regulating gall bladder contraction.

Hyperreflexia, a condition characterized by contractions of the urinary bladder, is not mediated by a micturition reflex. The contractions can be of neurogenic origin through spinal or supraspinal reflexes or of myogenic origin, independent of neuronal mediation. There is a clear relationship between hyperreflexia and symptoms such as urgency, frequency, nocturia and urinary incontinence. Therapies to reduce the presence of uninhibited bladder contractions include oral drug therapy, instillation drug therapy and parasympathetic nerve ablation. The current study characterizes the ability of terodiline to inhibit an experimental form of hyperreflexia and compares the efficacy and potency of terodiline and other agents on hyperreflexia and evoked contractions. The results can be summarized as follows: (1) terodiline inhibits the amplitude of the hyperreflexia at lower concentrations than it inhibits the frequency of hyperreflexia; (2) terodiline had no statistically significant effect on mean blood pressure at any concentration utilized; (3) terodiline had approximately the same potency for inhibition of 2 and 32 Hz stimulation for both the bladder body and base; (4) terodiline inhibited the maximum contractile response to bethanechol and also shifted the curve to the right, demonstrating that terodiline is a mixed inhibitor, and (5) terodiline was a noncompetitive inhibitor of KCl.

Streptozocin-induced diabetes in rats causes changes in urinary bladder function and increases the responsiveness of isolated bladder strip preparations to contractile agents and field stimulation. We monitored the role of extracellular glucose in the contractile responsiveness of bladder body strips from control, 2-month diabetic, and sucrose-drinking rats to the muscarinic agonist bethanechol. Consumption of sucrose and induction of diabetes caused increases in bladder mass compared with that of controls. In the presence of normal glucose levels (5.6 mmol/L), bladder strips from diabetic rats responded to bethanechol with significantly larger responses than those from control or sucrose-drinking rats. Removal of glucose from the bathing medium caused time-dependent decreases in contractile response of bladder strips from all groups; there were no differences in the percent decrease in response between the three groups. The presence of insulin (100 mU/mL) had no effects on contractile responsiveness or the rate of decline of response. Following return of glucose to the medium, there were progressive increases in contractile responsiveness in all groups, which returned to original contractile values within 60 minutes and were unaffected by insulin. Pyruvate (9.1 mmol/L) was able to substitute for glucose in maintaining the contractile responses. Increasing the glucose concentration of the medium to 30 mmol/L had no effects on contractile responses. Unstimulated bladder adenosine triphosphate (ATP) and creatine phosphate concentrations were similar in control, diabetic, and sucrose-drinking rats. In conclusion, changes in glucose utilization and high-energy phosphate levels cannot explain the increased contractile responsiveness of bladder body strips from diabetic rats to contractile agents.

The NADH/NAD ratio is a measure of potential metabolic energy in smooth muscle tissue. Previous studies on bladder smooth muscle demonstrated that during active contraction when energy utilization is high, NADH is rapidly oxidized to NAD resulting in a decrease in the ratio of NADH/NAD. Intracellular systems utilizing ATP as an energy source are characterized by changes in the NADH/NAD ratio. This ratio can be monitored simultaneously with changes in smooth muscle tissue tone using an optical fiber probe which continually monitors NADH fluorescence and contractile activity of the same smooth muscle preparation. The present study correlates alterations in the ratio of NADH/NAD with both spontaneous and induced contractions and relaxations in the rabbit corpora cavernosa. The results show a high degree of correlation between a decrease in spontaneous fluorescence (decrease in the NADH/NAD ratio) and spontaneous contraction. An increase in tension was followed in time by a decrease in the NADH/NAD ratio. This was consistent for all strips showing significant spontaneous activity. ATP caused a rapid decrease in tension which was correlated with a decrease in fluorescence. The relative decrease in NADH fluorescence was proportional to the relative decrease in tension. Under basal conditions (0.8 g passive tension) ATP and nitroprusside stimulated a marked reduction in tension, but only ATP stimulated a substantial decrease in NADH fluorescence. Bethanechol and isoproterenol relaxed the corporal tissue to a relatively small degree which correlated with relatively small decreases in fluorescence. Methoxamine stimulated a substantial contraction of corporal smooth muscle which correlated with a rapid and significant decrease in NADH fluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)