Effects of a M1 receptor antagonist, pirenzepine, a M2 receptor antagonist, AF-DX116, and a nicotinic receptor antagonist, mecamylamine on the pressor responses to preganglionic sympathetic nerve stimulation(PNS) and McN-A-343 and DMPP in spinal(pithed) rabbits were investigated in order to elucidate a functional role of M1, M2 and nicotinic receptors in ganglionic transmission. Pirenzepine and AF-DX116 selectively inhibited the McN-A-343-induced pressor reponse in chlorisondamine-treated rabbit and the BCh-induced bradycardia, respectively. Electrical stimulations of preganglionic sympathetic outflow at T8 level produced increases in blood pressure. Pirenzepine(3 microgram/kg) significantly inhibited the PNS-induced pressor response and the degree of inhibition was not changed by increasing the doses to 100 microgram/kg. AF-DX116(100 microgram/kg) had no effect on the PNS-induced pressor response. Mecamylamine inhibited the PNS-induced pressor response in a dose-dependent manner. The inhibitory action of mecamylamine was significantly augmented by combined-treatment with pirenzepine(30 microgram/kg) but AF-DX116(100 microgram/kg) did not affect the inhibitory action of mecamylamine. McN-A-343 and DMPP elicited pressor response in the spinal rabbit. Pirenzepine and AF-DX116 dose-dependently inhibited the McN-A-343-induced pressor response but they did not affect DMPP-induced pressor response. Mecamylamine inhibited both pressor responses induced by Mc-N-343- and DMPP. These results suggest that not only nicotinic receptors but also M1 receptors play a facilitatory role in ganglionic transmission but M2 receptors do not contribute the transmission in spinal(pithed) rabbits.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; Blood Pressure ; Bradycardia ; Dimethylphenylpiperazinium Iodide ; Electric Stimulation ; Ganglia, Sympathetic* ; Ganglion Cysts ; Mecamylamine ; Pirenzepine ; Rabbits ; Receptors, Nicotinic*

The present study was attempted to investigate the effect of strychnine on catecholamine (CA) secretion evoked by ACh, high K+, DMPP and McN-A-343 from the isolated perfused rat adrenal gland. The perfusion of strychnine (10-4 M) into an adrenal vein for 20 min produced great inhibition in CA secretory responses evoked by ACh (5.32X10-3 M), DMPP (10-4 M for 2 min) and McN-A-343 (10-4 M for 2 min), but did not alter CA secretion by high K+ (5.6X10-2 M). Strychnine itself did also fail to affect basal catecholamine output. Furthermore, in adrenal glands preloaded simultaneously with strychnine (10-4 M) and glycine (an agonist of glycinergic receptor, 10-4 M), CA secretory responses evoked by ACh, DMPP and McN-A-343 were considerably recovered to some extent when compared with those evoked by treatment with strychnine only. However, CA secretion by high K+ (5.6X10-2 M) was not affected. Taken together, these results demonstrate that strychnine inhibits greatly the CA secretory responses evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors, but does not affect that by membrane depolarization. It is suggested that strychnine-sensitive glycinergic receptors are localized in rat adrenal medullary chromaffin cells.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; Adrenal Glands* ; Animals ; Chromaffin Cells ; Dimethylphenylpiperazinium Iodide ; Glycine ; Membranes ; Perfusion ; Rats* ; Receptors, Cholinergic* ; Strychnine* ; Veins

Effect of acetylcholine(ACh) and McN-A-343 on porcine coronary artery and rabbit thoracic aorta were investigated in isolated preparations with or without intact endothelium. In the porcine coronary artery, ACh produced concentration dependent contraction which was greater in rings without the endothelium than in intact endothelial rings, but McN-A-343 did not alter the basel tension in both tissues. ACh relaxed contraction induced by 5-hydroxytryptamine(5-HT) in only intact endothelial rings, while NcN-A-343 inhibited the 5-HT induced tension in both preparations dose dependently. Carbachol elicited a prominent contraction in both tissues. The carbacol-induced tension was markedly inhibited by McN-A-343 in either rings with or without endothelium, while ACh contracted further the tension. ACh and McN-A-343 did not after the KCi induced tension, but clearly potentiated the contraction induced by Bay K 8644 in intact endothelial rings. In rabbit thoracic aorta, ACh elicited contraction in a concentration-dependent fashion which was potentiated by removal of endothelium, but McN-A-343 did not affect the basal tension of both rings. ACh inhibited the 5-HT-induced contraction in only intact endothelial ring, but McN-A-343 did not change the contraction of both rings. Conclusively, ACh produces endothelium-dependent relaxation in both arteries, while McN-A-343 elevated endothelium-independent inhibition to 5-HT or carbachol-induced tension.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride* ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Acetylcholine* ; Aorta, Thoracic ; Arteries* ; Carbachol ; Coronary Vessels ; Endothelium ; Relaxation ; Serotonin

The aim of the present study was designed to establish comparatively the inhibitory effects of D1-like and D2-like dopaminergic receptor agonists, SKF81297 and R(-)-TNPA on the release of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. SKF81297 (30 micrometer) and R-(-)-TNPA (30 micrometer) perfused into an adrenal vein for 60 min, produced great inhibition in the CA secretory responses evoked by ACh (5.32x10(-3) M), DMPP (10(-4) M), McN-A-343 (10(-4) M), high K+ (5.6x10(-2) M), Bay-K-8644 (10 micrometer), and cyclopiazonic acid (10 micrometer), respectively. For the release of CA evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid, the following rank order of inhibitory potency was obtained: SKF81297>R-(-)-TNPA. However, R(+)-SCH23390, a selectve D1-like dopaminergic receptor antagonist, and S(-)-raclopride, a selectve D2-like dopaminergic receptor antagonist, enhanced the CA secretory responses evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid only for 0~4 min. The rank order for the enhancement of CA release evoked by high K+, McN-A-343 and cyclopiazonic acid was R(+)-SCH23390>S(-)-raclopride. Also, the rank order for ACh, DMPP and Bay-K-8644 was S(-)-raclopride > R(+)-SCH23390. Taken together, these results demonstrate that both SKF81297 and R-(-)-TNPA inhibit the CA release evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors and the membrane depolarization from the isolated perfused rat adrenal gland without affecting the basal release, respectively, but both R(+)-SCH23390 and S(-)-raclopride facilitate the CA release evoked by them. It seems likely that the inhibitory effects of SKF81297 and R-(-)-TNPA are mediated by the activation of D1-like and D2-like dopaminergic receptors located on the rat adrenomedullary chromaffin cells, respectively, whereas the facilitatory effects of R(+)-SCH23390 and S(-)-raclopride are mediated by the blockade of D1-like and D2-like dopaminergic receptors, respectively: this action is possibly associated with extra- and intracellular calcium mobilization. Based on these results, it is thought that the presence of dopaminergic D1 receptors may play an important role in regulation of the rat adrenomedullary CA secretion, in addition to well-known dopaminergic D2 receptors.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla ; Animals ; Benzazepines ; Calcium ; Catecholamines ; Chromaffin Cells ; Dimethylphenylpiperazinium Iodide ; Indoles ; Membranes ; Rats ; Veins

The aim of the present study was to investigate the effects of 6-chloro-7,8-dihydroxy-1-phenyl-2,3, 4,5-tetrahydro-1H-3-benzazepine (SKF81297), a selective agonist of dopaminergic D1 receptor, on the secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane-depolarization in the isolated perfused rat adrenal gland, and also to elucidate the mechanism involved. SKF81297 (10~100microM) perfused into an adrenal vein for 60 min produced dose- and time-dependent inhibition of CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM), DMPP (100microM) and McN-A-343 (100microM). Also, in adrenal glands loaded with SKF81297 (30microM), the CA secretory responses evoked by Bay-K-8644 (10microM), an activator of L-type Ca2+ channels and cyclopiazonic acid (10microM), an inhibitor of cytoplasmic Ca2+-ATPase were also inhibited. However, in the presence of the dopamine D1 receptor antagonist, (R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-benzazepine-7-ol (SCH23390, 3microM), which is a selective antagonist of dopaminergic D1 receptor, the inhibitory responses of SKF81297 (30microM) on the CA secretion evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644, and cyclopiazonic acid were significantly reduced. Collectively, these experimental results suggest that SKF81297 inhibits the CA secretion from the rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) and membrane depolarization. This inhibitory of SKF81297 seems to be mediated by stimulation of dopaminergic D1 receptors located on the rat adrenomedullary chromaffin cells, which are relevant to extra- and intracellular calcium mobilization. Therefore, it is thought that the presence of the dopaminergic D1 receptors may be involved in regulation of CA release in the rat adrenal medulla.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Membranes ; Rats* ; Receptors, Dopamine D1 ; Veins

The present study was undertaken to investigate the effect of doxorubicin (DX) on secretion of catecholamines (CA) evoked by ACh, high K+, DMPP and McN-A-343 from the isolated perfused rat adrenal gland and to establish the mechanism of its action. DX (10(-7)~10(-6) M) perfused into an adrenal vein for 60 min produced relatively dose- and time-dependent inhibition of CA secretory responses evoked by ACh (5.32 X 10(-3) M), DMPP (10(-4) M) and McN-A-343 (10(-4) M). However, lower dose of DX did not affect CA secretion by high K+ (5.6 X 10(-2) M), but its higher doses depressed time-dependently CA secretion evoked by high K+. DX itself did also fail to affect basal CA output. In adrenal glands loaded with DX (3 X 10(-7) M), CA secretory responses evoked by Bay-K-8644, an activator of L-type Ca2+ channels and cyclopiazonic acid, an inhibitor of cytoplasmic Ca2+-ATPase were time-dependently inhibited. Furthermore, daunorubicin (3 X 10(-7) M), given into the adrenal gland for 60 min, attenuated CA secretory responses evoked by ACh, high K+, DMPP and McN-A-343. Taken together, these results suggest that DX causes relatively dose- and time-dependent inhibition of CA secretory responses evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors from the isolated perfused rat adrenal gland. However, lower dose of DX did not affect CA secretion by high K+, and higher doses of DX reduced time-dependently CA secretion of high K+. It is thought that these effects of DX may be mediated by inhibiting both influx of extracellular calcium into the rat adrenomedullary chromaffin cells and intracelluar calcium release from the cytoplasmic store. Also, there was no difference in the mode of action between DX and daunorubicin in rat adrenomedullary CA secretion.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Daunorubicin ; Dimethylphenylpiperazinium Iodide ; Doxorubicin* ; Rats* ; Veins

The present study was designed to clarify whether tacrine affects the release of catecholamines (CA) from the isolated perfused model of rat adrenal gland or not and to elucidate the mechanism of its action. Tacrine (3 X 10(-5)~3 X 10(-4) M) perfused into an adrenal vein for 60 min inhibited CA secretory responses evoked by ACh (5.32 X 10(-3) M), DMPP (a selective neuronal nicotinic agonist, 10(-4) M for 2 min) and McN-A-343 (a selective muscarinic M1-agonist, 10(-4) M for 2 min) in relatively dose- and time- dependent manners. However, tacrine failed to affect CA secretion by high K+ (5.6 X 10(-2) M). Tacrine itself at concentrations used in the present experiments did not also affect spontaneous CA output. Furthermore, in the presence of tacrine (10(-4) M), CA secretory responses evoked by Bay-K-8644 (an activator of L-type Ca2+ channels, 10(-4) M), but not by cyclopiazonic acid (an inhibitor of cytoplasmic Ca2+-ATPase, 10(-4) M), was relatively time-dependently attenuated. Also, physostigmine (10(-4) M), given into the adrenal gland for 60 min, depressed CA secretory responses evoked by ACh, McN-A-343 and DMPP while did not affect that evoked by high K+. Collectively, these results obtained from the present study demonstrate that tacrine greatly inhibits CA secretion from the perfused rat adrenal gland evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors, but does fail to affect that by direct membrane-depolarization. It is suggested that this inhibitory effect of tacrine may be exerted by blocking both the calcium influx into the rat adrenal medullary chromaffin cells without Ca2+ release from the cytoplasmic calcium store, that is relevant to the cholinergic blockade. Also, the mode of action between tacrine and physostigmine in rat adrenomedullary CA secretion seems to be similar.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Neurons ; Nicotinic Agonists ; Physostigmine ; Rats* ; Tacrine* ; Veins

The aim of the present study was to investigate the effects of R-(-)-2,10,11-trihydroxy-N-propylnoraporphine [R-(-)-TNPA], a selective agonist of dopaminergic D2 receptor and S(-)-raclopride, a selective antagonist of dopaminergic D2 receptor, on the secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane-depolarization in the isolated perfused model of the rat adrenal gland, and also to establish its mechanism of action. R-(-)-TNPA (10~100 micrometer) perfused into an adrenal vein for 60 min produced dose- and time-dependent inhibition in CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM), DMPP (100 micrometer) and McN-A-343 (100 micrometer). R-(-)-TNPA itself did also fail to affect basal CA output. Also, in adrenal glands loaded with R-(-)-TNPA (30 micrometer), the CA secretory responses evoked by Bay-K-8644 (10 micrometer), an activator of L-type Ca2+ channels and cyclopiazonic acid (10 micrometer), an inhibitor of cytoplasmic Ca2+-ATPase were also inhibited. However, S(-)-raclopride (1~10 micrometer), given into an adrenal vein for 60 min, enhanced the CA secretory responses evoked by ACh, high K+, DMPP and McN-A-343 only for the first period (4 min), although it alone has weak effect on CA secretion. Moreover, S(-)-raclopride (3.0 micrometer) in to an adrenal vein for 60 min also augmented the CA release evoked by BAY-K-8644 and cyclopiazonic acid only for the first period (4 min). However, after simultaneous perfusion of R-(-)-TNPA (30 micrometer) and S(-)-raclopride (3.0 micrometer), the inhibitory responses of R-(-)-TNPA (30 micrometer) on the CA secretion evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644, and cyclopiazonic acid were significantly reduced. Taken together, these experimental results suggest that R-(-)-TNPA greatly inhibits the CA secretion from the perfused rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) and membrane depolarization, but S(-)-raclopride rather enhances the CA release by them. It seems that this inhibitory of R-(-)-TNPA may be mediated by stimulation of inhibitory dopaminergic D2 receptors located on the rat adrenomedullary chromaffin cells, while the facilitatory effect of S(-)-raclopride is due to the blockade of dopaminergic D2 receptors, which are relevant to extra- and intracellular calcium mobilization. Therefore, it is thought that dopaminergic D2 receptors may be involved in regulation of CA release in the rat adrenal medulla.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Membranes ; Perfusion ; Rats* ; Veins

BACKGROUND: The aim of this study was to examine whether PD 123319 (an angiotensin II type 2 [AT2] receptor antagonist) can influence the release of catecholamines (CA) from the perfused model of the rat adrenal medulla. METHODS: The adrenal gland was isolated by the modification of Wakade method, and perfused with normal Krebs-bicarbonate solution. The content of CA was measured using the fluorospectrophotometer. RESULTS: During perfusion of PD 123319 (range, 5 to 50 nM) into an adrenal vein for 90 minutes the CA secretory responses evoked by acetylcholine (ACh), high K+, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), and McN-A-343 was dose- and time-dependently inhibited. Furthermore, loading with PD 123319 for 90 minutes also markedly inhibited the CA secretory responses evoked by 4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoro-methyl-phenyl)-pyridine-5-carboxylate (Bay-K-8644), cyclopiazonic acid, veratridine, and angiotensin II (Ang II). PD 123319 did not affect basal CA output. Simultaneous perfusion of PD 123319 and CGP 42112 perfused into an adrenal vein for 90 minutes rather more potently inhibited the CA seretory responses evoked by Ach, high K+, DMPP, Bay-K-8644, veratridine, and Ang II compared to the inhibitory effect by PD123319-treated alone. CONCLUSIONS: Taken together, these results show that PD 123319 inhibits the CA secretion evoked by both cholinergic and Ang II receptor stimulation from the perfused rat adrenal medulla. This inhibitory effect of PD 123319 seems to be exerted by blocking the influx of both Na+ and Ca2+ through their voltage-dependent channels into the rat adrenomedullary chromaffin cells as well as by reducing the Ca2+ release from its cytoplasmic calcium store, which may be relevant to AT2 receptor blockade. Based on these present data, it is thought that PD 123319 has different activity from previously known AT2 antagonist activity in the perfused adrenal medulla, and that AT2 receptors may be involved in the rat adrenomedullary CA secretion.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Acetylcholine ; Adrenal Glands ; Adrenal Medulla ; Angiotensin II ; Angiotensin II Type 2 Receptor Blockers ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Imidazoles ; Indoles ; Oligopeptides ; Perfusion ; Pyridines ; Rats ; Veins ; Veratridine

BACKGROUND: The present study was attempted to compare enalapril, an angiotensin-converting enzyme inhibitor with losartan an angiotensin II (Ang II) receptor blocker in the inhibitory effects on the secretion of catecholamines (CA) from the perfused model of the rat adrenal gland. METHODS: The adrenal gland was isolated and perfused with Krebs-bicarbonate. CA was measured directly by using the fluorospectrophotometer. RESULTS: Both enalapril and losartan during perfusion into an adrenal vein for 90 minutes inhibited the CA release evoked by acetylcholine (ACh), 1.1-dimethyl-4-phenyl piperazinium (DMPP, a selective Nn agonist), high K+ (a direct membrane-depolarizer), 3-(m-chloro-phenyl-carbamoyl-oxy-2-butynyl-trimethyl ammonium (McN-A-343, a selective M1 agonist), and Ang II in a time-dependent manner. Also, in the presence of enalapril or losartan, the CA release evoked by veratridine (an activator of voltage-dependent Na+ channels), 6-dimethyl-3-nitro-4-(2-trifluoromethyl-phenyl)-pyridine-5-carboxylate (BAY-K-8644, an L-type Ca2+ channel activator), and cyclopiazonic acid (a cytoplasmic Ca2+-ATPase inhibitor) were significantly reduced. Based on the same concentration of enalapril and losartan, for the CA release evoked by ACh, high K+, DMPP, McN-A-343, Ang II, veratridine, BAY-K-8644, and cyclopiazonic acid, the following rank order of inhibitory potency was obtained: losartan > enalapril. In the simultaneous presence of enalapril and losartan, ACh-evoked CA secretion was more strongly inhibited compared with that of enalapril- or losartan-treated alone. CONCLUSIONS: Collectively, these results demonstrate that both enalapril and losartan inhibit the CA secretion evoked by activation of both cholinergic and Ang II type-1 receptors stimulation in the perfused rat adrenal medulla. When these two drugs were used in combination, their effects were enhanced, which may also be of clinical benefit. Based on concentration used in this study, the inhibitory effect of losartan on the CA secretion seems to be more potent than that of enalapril.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Acetylcholine ; Adrenal Glands ; Adrenal Medulla ; Ammonium Compounds ; Angiotensin II ; Animals ; Catecholamines ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Enalapril* ; Losartan* ; Perfusion ; Rats ; Veins ; Veratridine