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We histologically examined the effects of all-trans retinoic acid (ATRA) on neuronal injury induced by intravitreous injection of N-methyl-d-aspartic acid (NMDA) (200nmol/eye). Treatment with ATRA for 7 days (15mg/kg for the first two days and 10mg/kg for the following five days, p.o.) reduced the decrease of cell number in the ganglion cell layer and the inner nuclear layer 7 days after NMDA injection. TUNEL staining 6h after NMDA injection showed that treatment with ATRA (15mg/kg, p.o.) 1h prior to NMDA injection reduced the number of apoptotic cells in the ganglion cell layer and inner nuclear layer. The anti-apoptotic effect of ATRA was vanished by intravitreous injection of U0126, an extracellular signal-regulated kinase/mitogen-activated protein kinase kinase inhibitor (1nmol/eye). These results suggest that ATRA has a protective effect, which is medicated by extracellular signal-regulated kinase pathway, on NMDA-induced apoptosis in the rat retina. ATRA may be useful as a therapeutic drug against retinal diseases that cause glutamate neurotoxicity.

beta-Adrenergic stimulation enhances the activity of L-type Ca(2+) channels through mechanisms mediated by adenosine 3'5'-cyclic monophosphate (cAMP) and protein kinase A in cardiac myocytes. However, in smooth muscle cells, the effect of beta-adrenoceptor stimulation on the L-type Ca(2+) channel activity has been controversial, and the exact mechanism is still unclear. The present study was aimed at elucidating the effect of beta-adrenergic stimulation upon the activity of L-type Ca(2+) channels in guinea-pig detrusor smooth muscle cells. Isoproterenol (0.1-1 microM) inhibited Ba(2+) currents through L-type Ca(2+) channels (I(Ba)). Isoproterenol (0.1 microM) shifted the steady-state inactivation curve to negative voltages by 11 mV without affecting activation curves. The stimulation of cAMP-mediated signal transduction pathway by forskolin, 8-bromoadenosine 3'5'-cyclic monophosphate (8-Br-cAMP), or the intracellular application of cAMP also mimicked the effects of isoproterenol on I(Ba), which was blocked by the inhibition of protein kinase A. These results indicate that, in detrusor smooth muscles, the stimulation of beta-adrenoceptors exerts negative modulation of L-type Ca(2+) channels via cAMP/protein kinase A-dependent mechanism.

D-cis-[N-Methyl-3H]-3-(acetyloxy)-5-[2-[[2-(3,4-dimethoxyphenyl)ethyl]-methylamino]ethyl]-2,3-dihydro-2-(4-methoxyphenyl)-1,5-benzothiazepine-4(5H)-one ([3H]DTZ323), a novel 1,5-benzothiazepine radioligand, was characterized in a ligand-receptor binding study. Specific binding of [3H]DTZ323 to rabbit skeletal muscle T-tubule membranes was saturable and reversible. Scatchard analysis indicated a single binding site with a K(d) value of 1.4 and 1.8 nM at 25 and 37 degrees C, respectively. DTZ323 and diltiazem derivatives inhibited specific [3H]DTZ323 binding with a rank order of DTZ323>DTZ417 (quaternary ammonium derivative of DTZ323)>diltiazem>L-cis-DTZ323. The affinity of DTZ323 was 51 times higher than that of diltiazem. [3H]DTZ323 binding was also completely inhibited by verapamil and tetrandrine, thus revealing the unique nature of the diltiazem-binding site. Specific [3H]DTZ323 binding to crude guinea pig ventricular membranes was inhibited by diltiazem, DTZ323 and its derivatives with IC(50) values close to those previously reported for the blockade of L-type Ca(2+) channel currents. These results indicate that [3H]DTZ323 is a potent and selective radioligand for the diltiazem-binding site of L-type Ca(2+) channels.

The effects of L-cis and D-cis diltiazem on the extracellular potassium concentration ([K(+)]e), pH and cardiac function were compared in ischemic guinea pig hearts. Before inducing ischemia, L-cis diltiazem (10 and 30 microM) reduced the left ventricular developed pressure (LVDP) with a marginal inhibition of heart rate (HR), whereas lower doses of the D-cis isomer decreased both LVDP and HR. L-cis Diltiazem only slightly inhibited the increase in [K(+)]e and the decrease in pH but significantly inhibited ischemic contractures in contrast to the marked inhibition of these parameters produced by even low doses of the D-cis isomer. Notably, at equipotent doses for the ischemic parameters, L-cis diltiazem restored the left ventricular end-diastolic pressure (LVEDP) and HR after reperfusion to a greater extent than the D-cis isomer. These results suggest that the L-cis isomer may specifically improve postischemic function, in addition to the modest action on [K(+)]e and pH, in guinea pig hearts.

Recently, it has been demonstrated that the production of prostaglandins and thromboxane is increased in patients with chronic glomerulonephritis and lupus nephritis. We recently demonstrated that thromboxane A(2) delayed the clearance of heat-aggregated bovine serum albumin deposited in glomeruli. In the present study, we investigated the effect of thromboxane A(2) on the clearance of macromolecules in nephritic glomeruli. First, we attempted to clarify the conditions for the clearance of heat-aggregated bovine serum albumin in nephritic glomeruli, using glomeruli isolated from control and anti-glomerular basement membrane nephritic mice. Heat-aggregated bovine serum albumin was injected twice into each mouse. The glomeruli were then isolated and incubated in culture medium. The heat-aggregated bovine serum albumin content of control glomeruli gradually diminished with incubation time up to 24 h. The heat-aggregated bovine serum albumin content of nephritic glomeruli was 69% higher than that of control glomeruli at 24 h incubation. The production of thromboxane B(2) (the stable metabolite of thromboxane A(2)) in nephritic glomeruli showed about a sevenfold increase compared with control. DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydro-naphthalene-2-carboxylic acid hydrochloride], a thromboxane A(2) synthase inhibitor, and KT2-962 [sodium 3-(4-(4-chlorophenyl-butylsulfonamido) butyl)-6-isopropylazulene-1-sulfonate], a selective thromboxane A(2) receptor antagonist, significantly reduced the heat-aggregated bovine serum albumin content in nephritic glomeruli. Normal glomeruli treated with U-46619 [15S-hydroxy-11a,9a-(epoxymethano)prosta-5Z,13E-dienoic acid], a stable analogue of thromboxane A(2), had significantly more heat-aggregated bovine serum albumin than control glomeruli. We next investigated whether thromboxane A(2) could affect the uptake/disposal of heat-aggregated bovine serum albumin by cultured rat mesangial cells. U-46619 significantly enhanced the uptake and inhibited the disposal of heat-aggregated bovine serum albumin by mesangial cells. Finally, we performed experiments to elucidate the role of the thromboxane A(2) receptor (TP receptor) in the clearance of heat-aggregated bovine serum albumin using TP-deficient mice. The glomerular heat-aggregated bovine serum albumin content of TP-receptor knockout [TP(-/-)] mice was lower than that of wild-type [WT(+/+)] mice. U-46619 dose dependently increased the uptake of heat-aggregated bovine serum albumin by mesangial cells in WT(+/+) mice, but not in the TP(-/-) mice. These findings suggest that thromboxane A(2) retards the clearance of aggregated protein in nephritic glomeruli and may contribute to the pathophysiology of glomerulonephritis.

Detrusor muscle relaxes upon activation of beta-adrenoceptors on smooth muscle cells. However, the mechanism of relaxation following the stimulation of beta-adrenoceptors remains unclear. In order to clarify the mechanism, we investigated the involvement of ion channels in bladder relaxation. In guinea-pig isolated bladder strips precontracted by high-K(+), isoproterenol caused concentration-dependent relaxation. The relaxation caused by isoproterenol (1 microM) was larger in 30 mM K(+) than in 120 mM K(+) (54.2+/-8.0% and 18.2+/-4.1% of papaverine-induced relaxation, respectively, n=4). Iberiotoxin (100 nM) inhibited the isoproterenol-induced relaxation (vehicle 69.5+/-8.0% vs. iberiotoxin 24.9+/-6.2%, respectively, n=5). Whole-cell patch-clamp recording revealed that isoproterenol as well as forskolin increased the iberiotoxin-sensitive K(+) currents, and this increase was abolished by protein kinase inhibitor. These results suggest that the isoproterenol-induced relaxation of guinea-pig bladder smooth muscle is mainly mediated by facilitation of BK(Ca) channels subsequent to the activation of the cAMP/protein kinase A pathway.

We have previously demonstrated that treatment with L-cis diltiazem reduced cardiac infarct size in vivo. To examine the effect of L-cis diltiazem on Ca(2+) overload induced by ischemia/reperfusion, we used a model for Ca(2+) overload produced by metabolic inhibition in isolated guinea pig myocytes. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was quantified by fura-2 fluorescence microscopy and Ca(2+) overload was induced by inclusion of 1 microM of carbonyl cyanide m-chrolophenylhydrazone (CCCP) for 40 min treatment followed by washout for 30 min. This treatment caused a large [Ca(2+)](i) elevation as well as a sustained contracture of the cardiomyocytes. The increase was suppressed by 10 microM of 2-[2-[4-(4-nitrobenzyloxy) phenyl] ethyl] isothiourea methanesulphonate (KB-R7943), a specific inhibitor of the Na(+)/Ca(2+) exchanger, but not by nitrendipine (10 microM). L-cis Diltiazem (10 microM) attenuated the [Ca(2+)](i) increase, suggesting that L-cis diltiazem elicits a cardioprotective effect via attenuation of the [Ca(2+)](i) increase induced by metabolic inhibition and energy repletion.

In order to examine some possibly misleading conclusions of the pharmacological analysis of the signal transduction pathways of gastric acid secretion, we evaluated various agents including inhibitors of protein kinase C, cyclic AMP-dependent protein kinase, phospholipase C, phospholipase A2, lipoxygenase, casein kinase, calmodulin, myosin light chain kinase, tyrosine kinase, anion exchanger, and protein phosphatase; and activators of protein kinase C. Among them, the cyclic AMP-dependent protein kinase inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinylsulfonamide (H-89), the phospholipase A2 inhibitor 2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid (ONO-RS-082), three myosin light chain kinase inhibitors (1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-7), 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), and wortmannin), the anion exchanger inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), the phospholipase C inhibitor neomycin, and most known calmodulin antagonists strongly inhibited [14C]aminopyrine accumulation, an indicator of acid secretion, in isolated rabbit gastric glands stimulated by N6,2'-O-dibutyryl-cyclic AMP. ONO-RS-082, calmidazolium, and DIDS inhibited H+,K+-ATPase. Most of the chemicals with antisecretory activity showed protonophore-like activity in gastric microsomes as well as in the mitochondria. It is concluded that H-89, ONO-RS-082, ML-7, ML-9, neomycin, and all calmodulin antagonists tested so far should not be used as tools to analyze gastric acid secretion.

We have previously shown, in a radioligand binding study with single ventricular myocytes, that benzothiazepine and dihydropyridine binding sites interact with each other. To further examine whether this interaction between the two binding sites is reflected in the function of L-type Ca2+ channels, the blocking action of diltiazem, nitrendipine, and the combination of these two drugs on L-type Ca2+ channel currents was investigated using baby hamster kidney cells expressing the alpha 1C, alpha 2/delta, beta and gamma subunits of the Ca2+ channel. The effects of diltiazem and nitrendipine were additive at room temperature but synergistic at 33 degrees C. The use-dependent block by 3 microM of diltiazem was significantly enhanced from 28% to 68% by addition of 30 nM of nitrendipine, which by itself did not have a blocking effect. Thus, we conclude that benzothiazepine- and dihydropyridine binding sites interact and potentiate their blocking action on L-type Ca2+ channels in a temperature-dependent manner.

The aim of the present study was to determine the effect of 5-hydroxydecanoate (5-HD) on extracellular K+ levels during global ischemia for 30 min employing K+-sensitive electrodes in isolated guinea-pig hearts. 5-HD (100 microM) reduced the K+ accumulation during the early period of ischemia, but did not inhibit the elevation of extracellular K+ in the latter half of the ischemic period which was selectively enhanced by ouabain (3 microM). Thus, 5-HD appears to exert a similar mode of action as glibenclamide on extracellular K+ accumulation in the ischemic guinea-pig hearts. The present study also strengthens the previous conclusion that an ATP-sensitive K+ channel contributes only to the initial increasing phase of extracellular K+ accumulation during ischemia in guinea-pig hearts.

The antinephritic effect of lipo-prostaglandin E1, prostaglandin E1 ((1R,2R,3R)-3-hydroxy-2-[(E)-(3S)-3-hydroxy-1-octenyl]-5-oxocyclopent ane heptanoic acid) incorporated in lipid microspheres was investigated using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Lipo-prostaglandin E1 was given i.v. twice a day at 20, 40 and 80 microg/kg and azathioprine, an immunosuppressive agent, at 20 mg/kg was given p.o. once daily from the autologous phase, in which glomerulonephritis was fully developed (the 21 st day after injection of the anti-glomerular basement membrane serum), to the 50th day. Lipo-prostaglandin E1 (40 and 80 microg/kg x 2 per day) significantly inhibited the development of glomerular alterations as well as the elevation of proteinuria and plasma creatinine. Lipo-prostaglandin E1 (20 microg/kg x 2 per day) and azathioprine (20 mg/kg per day) significantly inhibited only the glomerular histopathological changes. Lipo-prostaglandin E1 at three doses significantly decreased the deposition of both rabbit immunoglobulin G and rat immunoglobulin G on the glomerular basement membrane in nephritic rats, but azathioprine apparently inhibited only the deposition of rat immunoglobulin G. A single administration of lipo-prostaglandin E1 inhibited the elevation of platelet aggregation and restored the decrease in renal tissue blood flow in nephritic rats. In addition, a single administration of lipo-prostaglandin E1 inhibited the elevation of glomerular thromboxane B2 and 6-keto prostaglandin F1alpha production in nephritic rats. These results suggest that lipo-prostaglandin E1 may be an effective agent for the treatment of glomerulonephritis. Its antinephritic effect may be due to the inhibition of platelet aggregation, an increase in renal tissue blood flow, a decrease in rabbit and rat immunoglobulin G deposition, and amelioration of the abnormal metabolism of arachidonic acid.

The objective of the present study was to examine the effects of a long-acting angiotensin converting enzyme inhibitor, imidapril ((4S)-1-methyl-3-¿(2S)-2-[N-(1S)-1-ethoxycarbonyl-3-phenylpropyl) amino] propionyl¿-2-oxoimidazolidine-4-carboxylic acid hydrochloride), for 7 days on the cerebral blood flow autoregulatory response to hypotension in hypertensive rats. We measured the cerebral blood flow at rest and during hemorrhagic hypotension, using laser-Doppler flowmetry. At the same time, the absolute baseline cerebral blood flow values in the parietal cortex were quantified with the hydrogen clearance method. After administration of imidapril at a dose of 5 mg/kg/day for 7 days, the resting value of mean arterial blood pressure was significantly decreased by 25 mm Hg (P < 0.001), cerebral vascular resistance was lowered by 14.4% (P < 0.05) and the lower limit of cerebral blood flow autoregulation was shifted to a lower level, 106+/-11 mm Hg (mean +/- S.D.), from 137+/-8 mm Hg in the control group (P < 0.001), while resting cerebral blood flow remained unchanged. The present results demonstrated that imidapril preserves cerebral blood flow and significantly shifts the lower limit of cerebral autoregulation towards lower blood pressure levels.

The effects of a 1,5-benzothiazepine derivative, (+)-cis-3-(acetyloxy)-5-[2-[[2-(3,4-dimethoxyphenyl)ethyl]-methyla mino]ethyl]-2,3-dihydro-2-(4-methyoxyphenyl)-1,5-benzothiazepine-4 (5H)-one (DTZ323), on membrane currents were investigated in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. DTZ323 suppressed the L-type Ca2+ channel currents (I[Ca(L)]) more selectively than the T-type Ca2+ channel and the Na+ channel currents. DTZ323 inhibited I[Ca(L)] in a use- and a voltage-dependent manner with 24 times higher potency than that of diltiazem. Rate of recovery of I[Ca(L)] from the conditioned block by DTZ323 was faster compared with diltiazem and verapamil, and was steeply dependent on the holding potential at resting membrane potential range in ventricular myocytes (-90 to -60 mV). Our results suggest that DTZ323 is a selective Ca2+ channel antagonist, the most potent among the 1,5-benzothiazepine Ca2+ channel antagonists, and that the voltage- and use-dependent effect of DTZ323 on I[Ca(L)] is due to the steep voltage dependence of the rate of dissociation from the cardiac L-type Ca2+ channels.

To examine whether the modulation of the 1,4-dihydropyridine-binding by diltiazem derivatives, which has been shown in cardiac and skeletal muscle membranes, takes place in intact cardiac myocytes, effects of diltiazem on the specific binding of [3H](+)-PN200-110 to freshly isolated adult rat ventricular myocytes were investigated in normal Tyrode solution at 37 degrees C. Diltiazem consistently potentiated the [3H](+)-PN200-110-binding in a concentration-dependent manner, while DTZ323 (3-(acetyloxy)-5-[2-[[2- (3,4-dimethoxyphenyl)ethyl]-methylamino]ethyl]-2,3-dihydro-2(-4 methoxyphenyl)-1,5-benzothiazepin-4-(5H)-one), a potent diltiazem derivative, inhibited it in a non-competitive manner. In saturation studies, 100 microM decreased the Kd value of the 3[H](+)-PN200-110-binding (control, 0.102 +/- 0.008 vs. diltiazem, 0.074 +/- 0.004 (nM, n = 6), P < 0.05) without significant effect on Bmax (control, 65.7 +/- 6.4 vs. diltiazem, 76.7 +/- 4.4 (fmol/mg protein, n = 6). Moreover, membrane-impermeant quaternary diltiazem also potentiated the [3H](+)-PN200-110-binding in intact myocytes. These results suggest that diltiazem modulates the 1,4-dihydro-pyridine-binding even in intact cardiac myocytes, and the binding site of diltiazem is accessible from the extracellular side of the L-type Ca2+ channels.

The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane A2 synthase inhibitor, was evaluated using an experimental model of membranous nephropathy, viz. accelerated passive Heymann nephritis in which the glomerular injury is mediated by immune complexes. DP-1904 markedly inhibited the develop-ent of glomerular alteration as well as the elevation of proteinuria and plasma creatinine. When the treatment was started from the 22nd day, at which time proteinuria is fully developed, DP-1904 showed beneficial effects on proteinuria and glomerular histopathological changes. DP-1904 apparently decreased the deposition of both rabbit immunoglobulin G and rat immunoglobulin G on glomerular basement membrane in nephritic rats. A single administration of DP-1904 restored the decreased renal tissue blood flow, inhibited glomerular thromboxane B2 production and increased glomerular prostaglandin E2 and 6-keto prostaglandin F1 alpha production in nephritic rats. These results suggest that DP-1904 may be an effective agent for the treatment of idiopathic membranous nephropathy and that the beneficial effect of this drug may be due to the elimination of glomerular immune deposits and to an increase in renal tissue blood flow related to amelioration of the abnormal metabolism of arachidonic acid.

The pharmacological properties of T-0509, (-)-(R)-1-(3,4-dihydroxyphenyl)-2-[(3,4-dimethoxyphenethyl)amino]ethanol, were compared with those of isoproterenol. In the radioligand binding studies of [125I]iodocyanopindolol with COS-7 cell membranes that transiently expressed beta-adrenoceptor subtypes, T-0509 exhibited 11- and 97-fold greater Ki values for beta 2- and beta 3-adrenoceptors, respectively, compared with beta 1-adrenoceptors. Affinities of beta 2- and beta 3-adrenoceptors to isoproterenol were 1.4- and 28-fold lower than that of beta 1-adrenoceptors, respectively. The maximal stimulatory effects of T-0509 on adenylyl cyclase of CHO-K1 (chinese hamster ovary K1) cell membranes expressing beta 1- or beta 2-adrenoceptors were 85% or 96% of those produced by isoproterenol, respectively. These results indicate that T-0509 is a relatively specific beta 1-adrenoceptor agonist with a high intrinsic activity as compared with isoproterenol.

To investigate the flow-dependent contribution of basally released nitric oxide (NO) to vascular perfusion pressure, we compared the effects of a NO synthesis inhibitor on the pressure changes in some models of rate mesenteric vascular beds. Spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats (13-14-weeks-old) were used. The perfusion pressure at each flow rate was slightly higher in the SHR bed than in the WKY bed when no contractile compounds were applied. NG-Monomethyl-L-arginine (L-NMMA) significantly increased the pressure in WKY at flow rates more than 5 ml/min (8.9 mm Hg at 7 ml/min). L-NMMA increased the pressure in SHR at flow rates of 2-7 ml/min (40.2 mm Hg at 7 ml/min). L-NMMA markedly increased the pressure at each flow rate in both beds which methoxamine (30 microM) had constricted. The effects of L-NMMA were concentration-dependent, and were blocked by L-arginine. Therefore, basal NO release appears to contribute to the vasolidating tone although flow dependence of the effect is different in the absence or presence of an exogeneous tone in both hypertensive and normotensive rats.

We examined the effects of anandamide (N-arachidonoylethanolamine) on the binding of three types of Ca2+ channel antagonists for L-type Ca2+ channel, i.e., 1,4-dihydropyridine, 1,5-benzothiazepine and phenylalkylamine, to rabbit skeletal muscle membranes. Anandamide inhibited the binding of all three ligands. Arachidonic acid, a putative metabolite or a precursor of anandamide, inhibited 1,4-dihydropyridine binding, whereas it augmented both 1,5-benzothiazepine and phenylalkylamine binding. The involvement of prostaglandins synthesized from arachidonic acid was considered to be minor. These findings indicate that both anandamide and arachidonic acid interact not only with 1,4-dihydropyridine but also with 1,5-benzothiazepine and phenylalkylamine binding sites as a common feature of unsaturated lipids.

In order to investigate the effects of Ca2+, Ba2+ and Sr2+ on vascular endothelial nitric oxide (NO) production, contractile and relaxant responses of porcine depolarized coronary arteries to these divalent cations were compared. In the presence of diltiazem, Ba2+ induced NO-dependent relaxation, Sr2+ did slightly and Ca2+ did not; however all three cations increased cGMP levels in endothelium-intact arteries to similar extents. In the absence of diltiazem, these cations evoked contractions: the EC50 of Ca2+ for endothelium-denuded arteries was lower than those of Ba2+ and Sr2+. The IC50 of diltiazem for arteries precontracted with Ca2+ was higher than for arteries precontracted with Ba2+ and Sr2+. These results suggest that Ba2+ and Sr2+, as well as Ca2+, activate coronary arterial NO production, and also that the different responses of coronary arteries to these divalent cations can be explained, in part, by the different sensitivities of the smooth muscle to these cations and by the different potencies of diltiazem to inhibit the contractions the cations induced.

We report here the quantitative evaluation of binding density (Bmax) of [3H](+)-PN200-110 in aortic membranes obtained from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. At both 4 and 13 weeks of age, there were no significant differences in Bmax and the dissociation constants (Kd) of [3H](+)-PN200-110 binding between SHR and WKY rat aortas. Irrespective of strain, the Kd increased and the Bmax decreased with age. These results suggest that the number of Ca2+ channels in aortas of SHR and WKY rats are not significantly different, even when hypertension is established in SHR.

The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane A2 synthetase inhibitor, was compared with that of OKY-046, using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Test drugs were given p.o. once daily from the day after the the development of glomerular alteration as well as the elevation of proteinuria and plasma cholesterol. On the other hand, OKY-046 (20 mg/kg per day), a thromboxane A2 synthetase inhibitor, significantly inhibited only deterioration in the glomeruli. DP-1904 and OKY-046 inhibited glomerular thromboxane B2 production and increased glomerular prostaglandin E2 and 6-keto prostaglandin F1 alpha production in normal and nephritic rats. Both drugs inhibited the increase in platelet aggregability, restored decreased renal tissue blood flow to a near-normal level and decreased the deposition of rat immunoglobulin G on glomerular basement membrane in nephritic rats. These results suggest that DP-1904 may be an effective agent for the treatment of proliferative glomerulonephritis.

The antagonistic effects of (+)- and (-)-4-phenyl-1,2,3,4-tetrahydroisoquinoline (4PTIQ) on methamphetamine in the rat anococcygeus muscle were compared with those of cocaine and nomifensine. Methamphetamine contracted the anococcygeus muscle through the release of norepinephrine from noradrenergic nerve terminals. (+)-4PTIQ inhibited the methamphetamine-induced contractions more strongly than cocaine and nomifensine. (+)-4PTIQ had no potentiating effects on exogenous norepinephrine-induced contraction, which was considered to be an index of amine neuronal uptake blockade. On the other hand, (-)-4PTIQ, cocaine and nomifensine produced a significant leftward shift of the norepinephrine concentration-response curve, i.e. they showed a strong blocking effect on amine neuronal uptake. These results suggest that the inhibitory effects of (+)-4PTIQ on the action of methamphetamine are mediated by a mechanism other than inhibition of amine neuronal uptake.

The inhibitory effect of 4-phenyltetrahydroisoquinoline (4-PTIQ) on methamphetamine-induced dopamine release in the rat nucleus accumbens was investigated using a brain microdialysis method. Methamphetamine (10(-6) M) infusion through a microdialysis probe induced the release of dopamine. Although the uptake inhibitors, cocaine (3 x 10(-6) M) and nomifensine (10(-6) M), failed to block dopamine release, 4-PTIQ (10(-6 M) inhibited the dopamine-releasing effect of methamphetamine. 4-PTIQ did not affect the elevation of the extracellular dopamine level induced by high concentrations of nomifensine (10(-5) M) and cocaine (3 x 10(-5) M). 4-PTIQ was the weakest inhibitor of [3H]dopamine uptake by rat striatal synaptosomes. These results suggest that 4-PTIQ is a selective antagonist against the dopamine-releasing effect of methamphetamine in the nucleus accumbens.

5-Methoxy-N,N-dimethyltryptamine (5-MeODMT) and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) facilitate motoneuron excitability through 5-HT1C/5-HT2 receptors in rats. Using spinal cord slices prepared from adult rats, we recorded unitary cell discharges, evoked by local stimulation of the adjacent site, extracellularly in the motor nuclei of the ventral horn. 5-MeODMT, DOI, 5-hydroxytryptamine (5-HT), 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) and tandospirone facilitated the probability of firing in the motor nuclei, with 5-MeODMT and DOI being the most potent. The effect of 5-MeODMT was significantly suppressed by ketanserin (a 5-HT2 receptor-selective antagonist), spiperone (a 5-HT1A/5-HT2 receptor antagonist) and cyproheptadine (a 5-HT1C/5-HT2 receptor antagonist), but not by 3-tropanyl-3,5-dichlorobenzoate (MDL 72222, a 5-HT3 receptor-selective antagonist) or pindolol (a 5-HT1A/5-HT1B receptor antagonist). This suggests that 5-HT2 and/or 5-HT1C receptors are involved in the facilitatory effects of 5-HT receptor agonists on the synaptic activity of ventral horn cells.

Diltiazem, a benzothiazepine Ca2+ antagonist, has four stereoisomeric forms: d- and l-isomers of the cis and trans forms. All four isomers were shown to completely inhibit the binding of d-cis-[3H]diltiazem to rabbit T-tubule Ca2+ channels. The potency of the inhibition was in the order: d-cis greater than l-cis greater than d-trans = l-trans. The Hill slope for each inhibition was close to unity. The l-cis, d-trans and l-trans isomers had no effect on dissociation of the d-cis[3H]diltiazem-benzothiazepine receptor complex. These results indicate that all four isomers bind to benzothiazepine receptors. Furthermore, all of the isomers modulated (+)-[3H]PN200-110 binding. At 37 degrees C, only the d-cis isomer stimulated the binding, whereas the others showed inhibition. At 2 degrees C, all of them inhibited the binding. Both trans isomers exerted virtually the same, weak effects on the binding. It is concluded that the effects of diltiazem on radioligand binding to Ca2+ channels are highly stereospecific for the d-cis isomer.

In the guinea-pig mesenteric artery, transmitter release modulated by noradrenaline (NA) or yohimbine was estimated from changes in amplitude of the excitatory junction potential (e.j.p.) recorded from smooth muscle cells. NA decreased the amplitude of the e.j.p. with no change in the facilitation. Yohimbine antagonized the effect of NA on the e.j.p. amplitude and enhanced the facilitation of e.j.p.; the latter action was not antagonized by NA. TTX-resistant e.j.p.s evoked by stronger intensity of stimuli were not affected by NA or yohimbine. It is concluded that NA inhibits and yohimbine enhances the release of transmitter, and that the latter event involves prejunctional alpha-adrenoceptor-dependent and -independent processes.

The effects of bunazosin on the electrical and mechanical responses of smooth muscle cells elicited by exogenously applied noradrenaline (NA) and by perivascular nerve stimulation were studied in the isolated mesenteric artery and vein of the dog. NA (above 10(-7) M in the artery and above 3 X 10(-8) M in the vein) depolarized the membrane. Perivascular nerve stimulation evoked an excitatory junction potential (e.j.p.) and slow depolarization in both vessels. Bunazosin and prazosin inhibited the NA-induced depolarization and slow depolarization in the artery but not in the vein. The NA actions in the vein were inhibited by yohimbine. Bunazosin (above 10(-6) M) increased the amplitude of the e.j.p. but decreased the outflow of NA during nerve stimulation. The amplitude and conduction velocity of the compound action potential of perivascular nerves were inhibited by higher concentrations of bunazosin (above 10(-5) M). The results provide evidence that bunazosin has selective inhibitory actions at alpha 1-adrenoceptors. This drug exerted differential effects on the release of co-transmitters which generate the e.j.p. and the slow depolarization, as bunazosin increased the former and decreased the latter. This suggests that e.j.p. is generated by a substance other than NA.