Resveratrol Inhibits Nicotinic Stimulation-Evoked Catecholamine Release from the Adrenal Medulla

Resveratrol has been known to possess various potent cardiovascular effects in animal, but there is little information on its functional effect on the secretion of catecholamines (CA) from the perfused model of the adrenal medulla. Therefore, the aim of the present study was to determine the effect of resveratrol on the CA secretion from the isolated perfused model of the normotensive rat adrenal gland, and to elucidate its mechanism of action. Resveratrol (10~100micrometer) during perfusion into an adrenal vein for 90 min inhibited the CA secretory responses evoked by ACh (5.32 mM), high K+ (a direct membrane-depolarizer, 56 mM), DMPP (a selective neuronal nicotinic Nn receptor agonist, 100micrometer) and McN-A-343 (a selective muscarinic M1 receptor agonist, 100micrometer) in both a time- and dose- dependent fashion. Also, in the presence of resveratrol (30micrometer), the secretory responses of CA evoked by veratridine 8644 (an activator of voltage-dependent Na+ channels, 100micrometer), Bay-K-8644 (a L-type dihydropyridine Ca2+ channel activator, 10micrometer), and cyclopiazonic acid (a cytoplasmic Ca2+ -ATPase inhibitor, 10micrometer) were significantly reduced. In the simultaneous presence of resveratrol (30micrometer) and L-NAME (an inhibitor of NO synthase, 30micrometer), the CA secretory evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were recovered to a considerable extent of the corresponding control secretion compared with the inhibitory effect of resveratrol alone. Interestingly, the amount of nitric oxide (NO) released from the adrenal medulla was greatly increased in comparison to its basal release. Taken together, these experimental results demonstrate that resveratrol can inhibit the CA secretory responses evoked by stimulation of cholinergic nicotinic receptors, as well as by direct membrane-depolarization in the isolated perfused model of the rat adrenal gland. It seems that this inhibitory effect of resveratrol is exerted by inhibiting an influx of both ions through Na+ and Ca2+ channels into the adrenomedullary cells as well as by blocking the release of Ca2+ from the cytoplasmic calcium store, which are mediated at least partly by the increased NO production due to the activation of NO synthase.

D-Amphetamine Causes Dual Actions on Catecholamine Release from the Rat Adrenal Medulla

The present study was designed to examine the effect of d-amphetamine on CA release from the isolated perfused model of the rat adrenal gland, and to establish its mechanism of action. D- amphetamine (10~100microM), when perfused into an adrenal vein of the rat adrenal gland for 60 min, enhanced the CA secretory responses evoked by ACh (5.32x10-3 M), excess K+ (5.6x10-2 M, a membrane depolarizer), DMPP (10-4 M, a selective neuronal nicotinic Nn-receptor agonist) and McN-A-343 (10-4 M, a selective M1-muscarinic agonist) only for the first period (4 min), although it alone has weak effect on CA secretion. Moreover, d-amphetamine (30microM) in to an adrenal vein for 60 min also augmented the CA release evoked by BAY-K-8644, an activator of the dihydropyridine L-type Ca2+ channels, and cyclopiazonic acid, an inhibitor of cytoplasmic Ca2+ ATPase only for the first period (4 min). However, in the presence of high concentration (500microM), d-amphetamine rather inhibited the CA secretory responses evoked by the above all of secretagogues. Collectively, these experimental results suggest that d-amphetamine at low concentrations enhances the CA secretion from the rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) as well as by membrane depolarization, but at high concentration it rather inhibits them. It seems that d-amphetamine has dual effects as both agonist and antagonist at nicotinic receptors of the isolated perfused rat adrenal medulla, which might be dependent on the concentration. It is also thought that these actions of d-amphetamine are probably relevant to the Ca2+ mobilization through the dihydropyridine L-type Ca2+ channels located on the rat adrenomedullary chromaffin cell membrane and the release of Ca2+ from the cytoplasmic store.

Influence of Bradykinin on Catecholamine Release from the Rat Adrenal Medulla

The present study was undertaken to investigate the effect of bradykinin on secretion of catecholamines (CA) evoked by stimulation of cholinergic receptors and membrane depolarization from the isolated perfused model of the rat adrenal glands, and to elucidate its mechanism of action. Bradykinin (3 X 10 (-8) M) alone produced a weak secretory response of the CA. however, the perfusion with bradykinin (3 X 10 (-8) M) into an adrenal vein of the rat adrenal gland for 90 min enhanced markedly the secretory responses of CA evoked by ACh (5.32 X 10 (-3) M), excess K+ (5.6 X 10 (-2) M, a membrane depolarizer), DMPP (10 (-4) M, a selective neuronal nicotinic agonist) and McN-A-343 (10 (-4) M, a selective M1-muscarinic agonist). Moreover, bradykinin (3 X 10 (-8) M) in to an adrenal vein for 90 min also augmented the CA release evoked by BAY-K-8644, an activator of the dihydropyridine L-type Ca2+ channels. However, in the presence of (N-Methyl-D-Phe7) -bradykinin trifluoroacetate salt (3 X 10 (-8) M), an antagonist of BK2-bradykinin receptor, bradykinin no longer enhanced the CA secretion evoked by Ach and high potassium whereas the pretreatment with Lys- (des-Arg9, Leu8) -bradykinin trifluoroacetate salt (3 X 10 (-8) M), an antagonist of BK1-bradykinin receptor did fail to affect them. Furthermore, the perfusion with bradykinin (3 X 10 (-6) M) into an adrenal vein of the rabbit adrenal gland for 90 min enhanced markedly the secretory responses of CA evoked by excess K+ (5.6 X 10 (-2) M). Collectively, these experimental results suggest that bradykinin enhances the CA secretion from the rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) and membrane depolarization through the activation of B2-bradykinin receptors, not through B1-bradykinin receptors. This facilitatory effect of bradykinin seems to be associated to the increased Ca2+ influx through the activation of the dihydropyridine L-type Ca2+ channels.