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A post-marketing surveillance study reported fatalities following tissue plasminogen activator administration in acute aortic dissection (AAD) with the symptoms of acute ischemic stroke (AIS) patients. Therefore, it is important to discriminate AAD from AIS. The present study aimed to investigate whether fibrinogen/fibrin degradation products (FDP) value can be useful in differential diagnosis between AAD and AIS. The study group comprised 20 AAD patients (10 men and 10 women; age 63.9 ± 13.6 years) and 159 AIS patients (91 men and 68 women; age 74.2 ± 10.6 years) who were transported to our hospital from 2007 to 2012. The AAD cases were further divided into patent-type AAD and thrombosed-type AAD. FDP values were significantly higher in the AAD group than in the AIS group (18.15 [5.2 - 249.9] μg/ml vs. 2.3 [1.5 - 4.45] μg/ml ; P < 0.001). In AAD groups, FDP values were significantly higher in the patent-type AAD group (n = 9) than in the thrombosed type AAD group (n = 11) (293.2 μg/ml [63.1 - 419.6 μg/ml ] vs. 5.6 μg/ml [3.8 - 7.9 μg/ml ]. FDP values were significantly higher in patients with AAD than in those with AIS, especially those with patent-type AAD compared with AIS patients. High FDP values may be a useful marker for differential diagnosis between patent-type AAD and AIS.

Case reports of hyperammonemia due to urease-producing bacteria are found occasionally, but most of them are associated with urinary tract infections. We experienced a case of infectious enterocolitis with hyperammonemia in which the causative bacteria was speculated to be urease-producing bacteria. A Japanese woman in her 70s had been diagnosed with microscopic polyangiitis in a nearby hospital and was transferred to our hospital. Although the microscopic polyangiitis was relatively under control after treatment with steroids and rituximab, frequent diarrhea with hyperammonemia (324 µg/dl) appeared and she became comatose. Her blood ammonia decreased to 47 µg/dl and her consciousness recovered to a normal state after antibiotic treatment for infectious enterocolitis and ammonia detoxification therapy. Liver dysfunction, portosystemic shunt, excessive protein intake and constipation were not observed, and she took no medications that would cause hyperammonemia. Although culture results could not identify urease-producing bacteria, considering the clinical course, acute hyperammonemia was suspected to be due to urease-producing bacteria infection. It is necessary to consider the influence of urease-producing bacteria as a cause of acute hyperammonemia not only in urinary tract infections but also in infective enterocolitis.

Rat melanotrophs express several types of voltage-gated and ligand-gated calcium channels, although mechanisms involved in the maintenance of the resting intracellular Ca

Early direct current (DC) shock is the most important therapy for ventricular fibrillation. Following the increased availability of automated external defibrillators (AED), the survival rate of cardiopulmonary arrest patients with ventricular fibrillation has improved. Although patients with shock-resistant ventricular fibrillation require additional antiarrhythmic drug therapy, the optimal protocol has not been established. Nifekalant is a pure potassium channel blocker with a pyrimidinedione structure. Nifekalant was approved in Japan for the treatment of life-threatening ventricular tachyarrhythmias in 1999, and is widely used as a class III antiarrhythmic intravenous drug. Intravenous amiodarone was approved in Japan in 2007, and exhibits various effects on ion channels, receptors, sympathetic activity, and thyroid function. Nifekalant and amiodarone also exhibit many pharmacological and pharmacodynamic differences. As nifekalant has no negative inotropic effect and a rapid action and clearance with a short half-life, it has some advantages over amiodarone for use in cardiopulmonary resuscitation. Indeed, data from clinical and animal studies suggest that nifekalant is superior to amiodarone for resuscitation of cardiopulmonary arrest resulting from shock-resistant ventricular fibrillation. A 300-mg bolus intravenous injection of amiodarone is considered an overdose for resuscitation of shock-resistant ventricular fibrillation. Further clinical studies are required to evaluate the effects of nifekalant compared with amiodarone, and to determine the optimal dose of amiodaone, for resuscitation of shock-resistant ventricular fibrillation.

Introduction. Corynebacterium ulcerans (C. ulcerans) is a zoonotic pathogen that occasionally causes diphtheria-like symptoms in humans. Cases of C. ulcerans infection have been increasing in recent years, and C. ulcerans has been recognized as an emerging pathogen. Case presentation. Here we report a case of asphyxia death due to pseudomembrane caused by diphtheria toxin (DT)-producing C. ulcerans. This is, to our knowledge, the first fatal case of C. ulcerans infection in Japan. A strain of C. ulcerans was obtained from the patient’s pet cat and was confirmed to be identical to the patient’s isolate by sequencing of the 16S rRNA gene and the DT gene, by pulsed-field gel electrophoresis (PFGE) and by ribotyping. In the same way, it was revealed that the isolate in this case belonged to the same molecular type as the C. ulcerans 0102 isolated from the first case in Japan in a distant prefecture 15 years earlier, in 2001. Conclusion. DT-producing C. ulcerans can be contracted from a companion animal and causes human death if the appropriate treatment is delayed. The finding indicates that this molecular type of virulent C. ulcerans is currently widespread in Japan.

We herein present a rare case of acquired methemoglobinemia associated with alkaptonuria. Alkaptonuria is a congenital error of metabolism caused by the deficiency of homogentisic acid oxidase, which subsequently results in the accumulation of homogentisic acid (HGA) in body tissues. As renal dysfunction progresses, the level of HGA excretion in the urine decreases and the blood concentration of HGA increases. HGA oxidizes oxyhemoglobin to methemoglobin, which can induce multiple organ failure accompanied by tissue hypoxia, intravascular hemolysis and metabolic acidosis. The mortality of this disease is high when alkaptonuria is associated with the presence of methemoglobinemia; therefore, treatment should be carefully planned in such cases.

Accidental hypothermia is the state in which body temperature falls due for exposure to a chilly environment. In accidental hypothermia, the mortality rate is higher the lower the body temperature. We report a case of a consciousness disorder and severe hypothermia, with a body temperature below 28 degrees C, in which it later became clear that a cervical spinal cord injury had been caused by a small external force. A 70-year-old woman was transported to our hospital in an ambulance for consciousness disturbance and severe hypothermia. At the time of arrival, her rectal temperature was 26.2 degrees C. We promptly performed rewarming. Her consciousness level became clear, but paralysis and diminished sensation were observed below the C5 domain. We suspected cervical spinal cord injury and performed cervical magnetic resonance imaging. She was diagnosed as having C5 cervical spinal cord injury. When there is a consciousness disorder due to accidental hypothermia, it might not be possible to evaluate the neurological value of the cervical spinal cord injury correctly. The presence of cervical spinal cord injury should be considered when patients have a decreased consciousness level due to hypothermia.

A 47-year-old man was found at his home in a state of cardiopulmonary arrest. His family performed cardiopulmonary resuscitation on him. He was brought to our hospital by ambulance. On arrival, his pupils were dilated and his heart was in a state of ventricular fibrillation. After returning to spontaneous circulation by the cardiopulmonary resuscitation, the electrocardiogram revealed ST elevation at V2-V5. Cardiac catheterizatin revealed a left anterior descending coronary obstruction. Percutaneous coronary angioplasty was performed. On the 26th day after admission, acalculous cholecystitis was found. It was difficult to perform emergent surgery, because the patient was taking an anticoagulant drug. We performed PTGBA (percutaneous transhepatic gallbladder aspiration) on the same day, and the gallbladder inflammation was improved. We consider that PTGBA is an effective treatment for difficult cases of acalcuous cholecystitis.

Pituitary adenylate cyclase activating polypeptide (PACAP)-like immunoreactivity and its receptor mRNA have been reported in the supraoptic and the paraventricular nucleus (SON and PVN, respectively) and PACAP has been implicated in the regulation of magnocellular neurosecretory cell function. To examine the site and the mechanism of the action of PACAP in the neurosecretory cells, we measured AVP release from SON slice preparations and the cytosolic Ca2+ concentration ([Ca2+]i) from single dissociated SON neurons. PACAP at concentrations from 10(-12) to 10(-7) M increased [Ca2+]i in dissociated SON neurons in a dose-dependent manner. The patterns of the PACAP-induced [Ca2+]i increase were either sustained increase or cytosolic Ca2+ oscillations. PACAP (10[-7] M) increased [Ca2+]i in 27 of 27 neurons and glutamate (10[-4] M) increased [Ca2+]i in 19 of 19 SON neurons examined, whereas angiotensin II (10[-7] M) increased [Ca2+]i in only 15 of 60 SON neurons examined. PACAP at lower concentrations (10[-10] to 10[-8] M) increased [Ca2+]i in 70-80% of neurons examined. Although the onset and recovery of the PACAP-induced [Ca2+]i increase were slower than those observed with glutamate, the spatial distribution of the [Ca2+]i increases in response to the two ligands were similar: [Ca2+]i increase at the proximal dendrites was larger and faster and that at the center of the soma was smaller and slower. The PACAP-induced [Ca2+]i responses were abolished by extracellular Ca2+ removal, the L-type Ca2+-channel blocker, nicardipine, or by replacement of extracellular Na+ with N-methyl D-glucamine, and were partially inhibited by the Na+-channel blocker, tetrodotoxin. The N-type Ca2+-channel blocker, omega-conotoxin GVIA did not significantly inhibit the PACAP-induced [Ca2+]i responses. Furthermore, PACAP (10[-7] M) as well as glutamate (10[-4] M) increased AVP release from SON slice preparations, and extracellular Ca2+ removal or nicardipine inhibited the AVP release in response to PACAP. These results indicate that PACAP enhances Ca2+ entry via voltage-gated Ca2+ channels and increases [Ca2+]i, which, in turn, stimulates somatodendritic vasopressin release by directly activating PACAP receptors on SON neurons. The results also suggest that PACAP in the SON may play a pivotal role in the control of the neurohypophyseal function at the level of the soma or the dendrites.

In neurosecretory cells of the supraoptic nucleus (SON) of rats, pituitary adenylate cyclase activating polypeptide (PACAP) causes an increase in [Ca2+]i, and stimulates somatodendritic vasopressin (VP) release. In this report, to elucidate the ionic mechanism of the action of PACAP, membrane potentials and ionic currents were measured from SON neurones in slice preparations or from dissociated SON neurones. In the current clamp mode, PACAP depolarized membrane potentials of both phasic and non-phasic neurones and increased the firing rate. Moreover, simultaneous measurements of membrane potentials and [Ca2+]i revealed that the membrane depolarization correlated well with increases in [Ca2+]i. In the voltage-clamp mode, PACAP induced inward currents at a holding potential of -70 or -80 mV in a dose-dependent manner and the time course of the currents was similar to that of the PACAP-induced membrane depolarization. The averaged reversal potential of the PACAP-induced currents obtained from dissociated SON neurones was -33 mV, which was close to the reversal potential of non-selective cation currents in SON neurones. The currents were rapidly and reversibly inhibited by a cation-channel blocker, gadolinium. Analysis of synaptic inputs into SON neurones in slice preparations revealed that PACAP had little or no effects on the frequency of spontaneous excitatory and inhibitory postsynaptic currents. These results suggest that pituitary adenylate cyclase activating polypeptide (PACAP) activates PACAP receptors in the postsynaptic membrane of the supraoptic nucleus (SON) neurones, and that the activation of PACAP receptors leads to opening of non-selective cation channels, depolarization of the membrane potential, and increase in the firing rate in SON neurones. Such mechanisms may account for the PACAP-induced increase in [Ca2+]i and vasopressin (VP) release observed in SON neurones.

We have previously reported that voltage-dependent Ca 2+ (VDC) channels of rat melanotrophs are inhibited by prostaglandin E 2 (PGE 2 ). In this study, mechanisms involved in the inhibitory actions of PGE 2 receptors of rat melanotrophs were analysed using reverse transcriptase-polymerase chain reaction (RT-PCR), Ca 2+ -imaging and whole-cell, patch-clamp techniques with recently developed EP agonists, each of which is selective for the known four subclasses of EP receptors (EP 1-4 ). PGE 2 reversibly suppressed the cytosolic Ca 21 concentration ([Ca 2+ ] i ). The maximum reduction in [Ca 2+ ] i by PGE 2 was comparable to that by dopamine or to that by extracellular Ca 2+ removal. RT-PCR analysis of all four EP receptors revealed that EP 3 and EP 4 receptor mRNAs were expressed in the intermediate lobe. The effects of PGE 2 to suppress [Ca 2+ ] i were mimicked by the selective EP 3 agonist, ONO-AE-248, whereas three other EP agonists, ONO-DI-004 (EP 1 ), ONO-AE1-259 (EP 2 ) and ONO-AE1-329 (EP 4 ), had little or no effect on [Ca 2+ ] i . All four G-protein activated inward rectifying K + (GIRK) channel mRNAs were identified in intermediate lobe tissues by RT-PCR. Dopamine concentration-dependently activated GIRK currents, whereas PGE 2 did not activate GIRK currents, even at the concentration causing maximal inhibition of VDC channels. These results suggest that PGE 2 acts on EP 3 receptors to suppress Ca 2+ entry of rat melanotrophs by selectively inhibiting VDC channels of these cells. We have compared the possible cellular and molecular mechanisms of inhibition by dopamine and PGE 2 .

We have reported that supraoptic nucleus (SON) neurones are excited by prostaglandin E 2 (PGE 2 ) presumably via dual postsynaptic PG receptors, FP receptors and unidentified EP receptors, and that presynaptic EP receptors may also be involved in the excitation. In the present study, to clarify the receptor mechanism of the PGE 2 -mediated actions on SON neurones, we studied the pre- and postsynaptic effects of four newly developed EP agonists that are selective for each of the four EP receptors, EP 1 - 4 , on rat SON neurones using extracellular recording and whole-cell patch-clamp techniques. The EP 4 agonist ONO-AE1-329 mimicked the excitatory effects of PGE 2 , whereas the EP 1 agonist ONO-DI-004, the EP 2 agonist ONO-AE1-257 and the EP 3 agonist ONO-AE-248 had little or no effect. The effects of ONO-AE1-329 were unaffected by the EP 1 /FP/TP antagonist, ONO-NT-012, which potently suppressed the excitation caused by the FP agonist fluprostenol and PGE 2 . ONO-AE1-329 caused marked excitation when responses to fluprostenol were desensitized by repeated applications of fluprostenol. Patch-clamp analysis in SON neurones showed that ONO-AE1-329 induced inward currents at a holding potential of -70 mV and the reversal potential of the currents was -35.1′2.3 mV. On the other hand, the frequency of spontaneous inhibitory postsynaptic currents recorded from SON slice preparations was suppressed by ONO-AE-248, but unaffected by the other three EP agonists. These results suggest that SON neurones possess postsynaptic EP 4 receptors and that γ-aminobutyric acid neurones innervating SON neurones possess presynaptic EP 3 receptors in their terminals. Activation of the two EP receptors may be involved in the excitatory regulation of SON neurones by PGE 2 .

While magnocellular neurons in the supraoptic nucleus (SON) possess rich Gi/o-mediated mechanisms, molecular and cellular properties of G-protein-activated inwardly rectifying K(+) (GIRK) channels have been controversial. Here, properties of GIRK channels are examined by RT-PCR and whole-cell patch-clamp techniques in rat SON neurons. Patch clamp experiments showed that the selective GABAB agonist, baclofen, enhanced currents in a high K(+) condition. The baclofen-enhanced currents exhibited evident inward rectification and were blocked by the selective GABAB antagonist, CGP55845A, the IRK channel blocker, Ba(2+), and the selective GIRK channel blocker, tertiapin, indicating that baclofen activates GIRK channels via GABAB receptors. The GIRK currents were abolished by N-ethylmaleimide pretreatment, and prolonged by GTPγS inclusion in the patch pipette, suggesting that Gi/o proteins are involved. RT-PCR analysis revealed mRNAs for all four GIRK 1-4 channels and for both GABABR1 and GABABR2 receptors in rat SON. However, the concentration-dependency of the baclofen-induced activation of GIRK currents had an EC50 of 110 µM, which is about 100 times higher than that of baclofen-induced inhibition of voltage-dependent Ca(2+) channels. Moreover, baclofen caused no significant changes in the membrane potential and the firing rate. These results suggest that although GIRK channels can be activated by GABAB receptors via the Gi/o pathway, this occurs at high agonist concentrations, and thus may not be a physiological mechanism regulating the function of SON neurons. This property that the membrane potential receives little influence from GIRK currents seems to be uncommon for CNS neurons possessing rich Gi/o-coupled receptors, and could be a special feature of rat SON neurons.

A significant relationship between lactate clearance and mortality rates in cardiac arrest cases has been reported. However, the relationship between lactate clearance and neurologic outcomes in cardiac arrest cases is not clear. We examined lactate clearance in cardiac arrest cases induced by ventricular fibrillation. We investigated 13 patients with cardiac arrest induced by ventricular fibrillation from April, 2006 to March, 2012 in which therapeutic hypothermia was performed. Patients were classified into two groups: those with a favorable neurologic outcome (n=7) and those with a poor outcome (n=6). We compared lactate clearance levels between the two groups. There was no significant difference in lactate concentrations at admission and 8 or 24 hours lactate clearance between the two groups 8 or 24 hours after admission. This result suggests we may not predict the neurologic outcome of cardiac arrest cases induced by ventricular fibrillation using lactate clearance.

Background In the perioperative period, plasma osmotic pressure, systemic blood pressure, and blood volume often change dramatically. Arginine vasopressin is a key factor in the regulation of these parameters. This study was performed to evaluate the direct and the mechanism of the actions of propofol on arginine vasopressin release from magnocellular neurosecretory neurons in the rat supraoptic nucleus. Methods Somatodendritic arginine vasopressin release from supraoptic nucleus slice preparations was measured by radioimmunoassay. Ionic currents were measured using the whole-cell mode of the patch-clamp technique in supraoptic nucleus slice preparations or in single dissociated supraoptic nucleus neurons of the rat. Results Propofol at concentrations greater than 10(-5) M inhibited the arginine vasopressin release stimulated by potassium chloride (50 mM). This inhibition by propofol was not reversed by picrotoxin, a gamma-aminobutyric acid(A)(GABA(A)) receptor antagonist, whereas arginine vasopressin release induced by glutamate (10(-3) M) was also inhibited by propofol at a clinically relevant concentration (10(-6) M). The latter effect was reversed by picrotoxin. Propofol evoked Cl- currents at concentrations ranging 10(-6) to 10(-4) M. Propofol (10(-6) M) enhanced the GABA (10(-6) M)-induced current synergistically. Moreover, propofol (10(-6) M) prolonged the time constant of spontaneous GABA-mediated inhibitory postsynaptic currents. Furthermore, propofol (10(-5) M and 10(-4) M) reversibly inhibited voltage-gated Ca2+ currents, whereas it did not affect currents induced by glutamate (10(-3) M). Conclusions Propofol inhibits somatodendritic arginine vasopressin release from the supraoptic nucleus, and the enhancement of GABAergic inhibitory synaptic inputs and the inhibition of voltage-gated Ca2+ entry are involved in the inhibition of arginine vasopressin release.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been reported to stimulate melanotroph secretion, and PACAP-like immunoreactivity and expression of PACAP type I receptor messenger RNA have been identified in the pituitary pars intermedia (PI). The present study showed that PACAP messenger RNA is also expressed in the PI. To examine the mechanism of PACAP action in the PI, cytosolic Ca2+ concentrations ([Ca2+]i) and ionic currents were measured in acutely dissociated rat melanotrophs. In about 40% of the melanotrophs studied, PACAP induced an increase in [Ca2+]i, which was suppressed by extracellular Ca2+ removal; extracellular Na+ replacement; the blocker of L-type Ca2+ channels, nicardipine; or the secreto-inhibitory neurotransmitter, dopamine. The PACAP-induced [Ca2+]i increase was mimicked by activators of protein kinase A (PKA) and protein kinase C (PKC), Sp-diastereomer of cAMP and 1-oleoyl-2-acetyl-sn-glycerol, and was reduced by inhibitors of PKA and PKC, Rp-diastereomer of cAMP and staurosporine. Patch-clamp analysis revealed that PACAP caused inward currents with a reversal potential of -0.8 mV and facilitated voltage-dependent Ba2+ currents. It further revealed that PACAP-induced inward currents were mimicked by 1-oleoyl-2-acetyl-sn-glycerol and inhibited by staurosporine, and that Sp-diastereomer of cAMP facilitated Ba2+ currents. These results suggest that PACAP potentiates Ca2+ entry mechanisms of rat melanotrophs by activation of nonselective cation channels via PKC and facilitation of voltage-dependent Ca2+ channels via PKA.

A 71-year-old man, who was diagnosed with familial amyloidosis type I, was admitted for treatment of severe orthostatic hypotension associated with recurrent syncopal attacks. Head-up tilt testing demonstrated severe orthostatic hypotension (114/72 mmHg in the supine position and 62/34 mmHg in the upright position) with syncope or presyncope. Oral midodorine and fludrocortisone therapies failed to prevent his symptoms. After administration of subcutaneous erythropoietin, his blood pressure drop in the upright position was decreased and symptoms disappeared unassociated with improvement of anemia. Although previous reports have shown that the mechanism by which erythropoietin improves orthostatic hypotension is related to improvement in anemia, other mechanisms may also play a role.

Nifekalant (NIF) is a pure potassium channel blocker developed in Japan and it has been used widely for treating fatal ventricular tachyarrhythmia since 1999. Because intravenous amiodarone (AMD) was approved in 2007 in Japan, there have been few studies about the comparison of the efficacy of NIF and AMD for resuscitation after cardiopulmonary arrest patients due to shock-resistant ventricular fibrillation.

The primary aim for occupational health care is to appropriately control risks related to health problems arising in workplace environments which are caused by work methods. Lowering risks might not always prevent accidents or illnesses; but initial treatment after an accident or of ill workers is crucial work for occupational health care staff. By implementing appropriate initial treatment, it is possible to increase the survival rate of workplace accidents and decrease the rate of illness. Crisis management at the time of an accident is a very important function of occupational health. Thus there is a close relationship between occupational health care and emergency medicine.

A 54 year old man was brought to our hospital by ambulance. He had been injured by falling heavy steel. An examination was performed, and he was diag nosed as having sinking skull, acute extradural hematoma, trauma of the righ eye, right eye laceration, injury of the optic canal (right blind), and multipl fractures. Open fractures were observed in the right ring finger and little finger Simple fractures were observed in the zygomatic bone nasal bone and maxillary bone. An emergency operation (external skeletal fixation, taxis of the skull and maxillary bone, extradural hematoma depletion, suture of right eyelid) was performed. His life was saved by consistent team treatment from preoperation t postoperation. He was discharged from our hospital on foot at 45 days after th operation.

We encountered a case of wide QRS tachycardia with chronic atrial fibrillation in Wolff-Parkinson-White syndrome. Unique features were late onset of syncope attacks associated with this tachycardia at an advanced age of 72 years old without previous documentation of Wolff-Parkinson-White syndrome on electrocardiogram. He had a high likelihood of sudden cardiac death. Catheter ablation using CARTO system easily led to a successful ablation of the accessory pathway. The mechanism of late onset of the wide QRS tachycardia was attributed to possible changes of electrophysiologic properties including the atrio-ventricular node and/or the accessory pathway, and the unique location of the accessory pathway.

Prostaglandins (PGs) have been implicated in the regulation of vasopressin (VP) and oxytocin (OT) release in response to various stimuli. To examine the site and mechanism of actions of PGs, we studied effects of PGE2 and PG-receptor agonists on supraoptic nucleus (SON) neurones of rat hypothalamic slice preparations using extracellular recording and whole-cell patch-clamp techniques. PGE2 modulated the electrical activity of more than 80% of the neurones studied. The effects of PGE2 on both phasic and non-phasic neurones were mostly excitatory, and dose-dependent. The effects of PGE2 were mimicked by PGF2alpha or the FP agonist, fluprostenol, whereas PGD2 or the selective EP, IP or TP agonist was less effective or had no effect. The effects of PGE2 were unaffected by the EP1 antagonist, SC-51322, but reduced to 80% of control by the EP1/FP/TP antagonist, ONO-NT-012, which reduced the effects of fluprostenol to 32% of control. Moreover, some neurones responsive to PGE2 did not respond to fluprostenol. Patch-clamp analysis in SON slice preparations revealed that PGE2 at 10(-6) M depolarized the membrane potential by 3.9+/-0.3 mV from the resting membrane potential of -58.4+/-2.2 mV in the current-clamp mode. In the voltage-clamp mode, PGE2 induced inward currents at a holding potential of -70 or -80 mV, while it did not affect spontaneous excitatory postsynaptic currents. PGE2 induced currents also in dissociated SON neurones and the reversal potential of the currents was -35.5+/-0.9 mV, which was similar to that of currents induced by fluprostenol. These results suggest that SON neurones possess at least two types of PG receptors, FP receptors and EP receptors of a subclass different from EP1, EP2, or EP3, and that activation of these receptors leads to the opening of nonselective cation channels, membrane depolarization and increase of the action potential discharge.

1. Voltage-dependent Ca2+ currents of dissociated rat supraoptic nucleus (SON) neurones were measured using the whole-cell configuration of the patch-clamp technique to examine direct postsynaptic effects of GABAB receptor activation on SON magnocellular neurones. 2. The selective GABAB agonist baclofen reversibly inhibited voltage-dependent Ca2+ currents elicited by voltage steps from a holding potential of -80 mV to depolarized potentials in a dose-dependent manner. The ED50 of baclofen for inhibiting Ca2+ currents was 1.4 x 10-6 M. Baclofen did not inhibit low threshold Ca2+ currents elicited by voltage steps from -120 to -40 mV. 3. Inhibition of high threshold Ca2+ currents by baclofen was rapidly and completely reversed by the selective GABAB antagonists, CGP 35348 and CGP 55845A, when the antagonists were added at the molar ratio vs. baclofen of 10 : 1 and 0.01 : 1, respectively. It was also reversed by a prepulse to +150 mV lasting for 100 ms. 4. The inhibition of Ca2+ currents was abolished when the cells were pretreated with pertussis toxin for longer than 20 h or with N-ethylmaleimide for 2 min. It was also abolished when GDPbetaS was included in the patch pipette. When GTPgammaS was included in the patch pipette, baclofen produced irreversible inhibition of Ca2+ currents and this inhibition was again reversed by the prepulse procedure. 5. The inhibition of N-, P/Q-, L- and R-type Ca2+ channels by baclofen (10-5 M) was 24.1, 10.5, 3.1 and 3. 6 %, respectively, of the total Ca2+ currents. Only the inhibition of N- and P/Q-types was significant. 6. These results suggest that GABAB receptors exist in the postsynaptic sites of the SON magnocellular neurones and mediate selective inhibitory actions on voltage-dependent Ca2+ channels of N- and P/Q-types via pertussis toxin-sensitive G proteins, and that such inhibitory mechanisms may play a role in the regulation of SON neurones by the GABA neurones.

It has been recently reported that proadrenomedullin N-terminal 20 peptide (PAMP), which is secreted with adrenomedullin and catecholamines from the adrenal medulla, inhibits catecholamine release stimulated with nicotine. In the present study, to elucidate anticholinergic mechanisms of PAMP we employed the whole-cell patch-clamp and the intracellular Ca2+ imaging techniques in cultured bovine adrenal medullary cells. PAMP inhibited nicotinic currents and [Ca2+]i rises induced by nicotine in a dose-dependent manner (10(-9)-10(6) M). These inhibitions were selective, since PAMP alone did not induce any ionic currents, moreover it did not affect voltage-dependent Ba2+ currents or high K+ (50 mM)-induced [Ca2+]i rises. The onset of the inhibitory effect of PAMP (10(-6) M) was very rapid and reached a steady-state level within 10 sec. The effect of PAMP (10(-6) M) lasted for about 10-15 min. Desensitization process of the nicotinic current fitted to a single exponential function with a time constant of 6.4 +/- 0.3 sec. When PAMP (10(-6) M) simultaneously added with nicotine (10(-5) M), the desensitization process was facilitated and fitted to two exponentials with time constants of 0.46 +/- 0.08 and 2.5 +/- 0.8 sec. From the present results, the inhibition by PAMP of nicotinic currents which was well associated with that of nicotine induced [Ca2+]i rises leads to the attenuation of catecholamine release probably, at least in part, due to the facilitation of the desensitization process of the nicotinic currents.