Neuronal nitric-oxide synthase inhibition facilitates adrenergic neurotransmission in rat mesenteric resistance arteries.

The effects of nonselective nitric-oxide synthase (NOS) inhibitors [N-omega-nitro-L-arginine methyl ester (L-NAME) and N-omega-nitro-L-arginine (L-NNA)] and specific neuronal NOS (nNOS) inhibitor [vinyl-L-N-5-(1-imino-3-butenyl)-L-ornithine (L-VNIO)] on adrenergic nerve-mediated vasoconstriction were studied in rat perfused mesenteric vascular beds without endothelium. Perfusion of L-NAME, L-NNA, or l-VNIO markedly augmented vasoconstrictor responses to periarterial nerve stimulation (PNS; 2-8 Hz) without affecting vasoconstriction induced by exogenously injected norepinephrine (NE). Addition of L-arginine, a precursor for the synthesis of nitric oxide (NO), reversed the augmentation of the PNS response by l-NAME. The PNS (8 Hz)-evoked NE release in the perfusate was increased by L-NAME perfusion. In preparations treated with capsaicin [a depleter of calcitonin gene-related peptide (CGRP)-containing nerves], L-NAME did not augment vasoconstrictor responses to PNS or NE injection. Combined perfusion of CGRP(8-37) (a CGRP receptor antagonist) and L-NAME induced additive augmentation of the vasoconstrictor response to PNS but did not affect the response to NE injection. In preparations with active tone produced by methoxamine and in the presence of guanethidine, L-NAME perfusion did not affect the vasodilator response induced by PNS. Immunostaining of the mesenteric artery showed the presence of nNOS-like immunopositive nerve fibers, which were absent in arteries pretreated with capsaicin. These findings suggest that NO, which is released from perivascular capsaicin-sensitive nerves, presynaptically inhibits neurogenic NE release to modulate adrenergic neurotransmission.

Effect of adrenomedullin on adrenergic vasoconstriction in mesenteric resistance arteries of the rat.

Adrenomedullin (AM) is a hypotensive peptide that belongs to a family of peptides structurally related to calcitonin gene-related peptide (CGRP). The present study examined the effect of AM on adrenergic nerve-mediated vasoconstriction in rat perfused mesenteric vascular beds without endothelium. Perfusion of AM at 0.1 nM but not 10 nM increased vasoconstrictor responses to periarterial nerve stimulation (PNS) (1-4 Hz), while AM at 10 nM significantly attenuated vasoconstriction induced by bolus injection of norepinephrine (NE). In preparations treated with capsaicin (a CGRP depletor), pressor responses to both PNS and NE injection were markedly attenuated by AM. Perfusion of CGRP(8-37) (a CGRP-receptor antagonist) significantly potentiated the PNS- but not the NE-induced vasoconstriction. Combined perfusion of CGRP(8-37) and AM had no effect on the PNS-induced response and antagonized the inhibitory effect of AM on the NE-induced response. AM(2-52) (an AM-receptor antagonist) did not influence the effect of AM. These findings suggest that AM facilitates adrenergic vasoconstriction by inhibiting neurotransmission of CGRP-containing nerves, which counteract adrenergic nerve-mediated vasoconstriction.

SYMPATHETIC AND PARASYMPATHETIC INNERVATION OF RAT HEART AND THEIR RELATION / 解剖学报

Fifty two adult male rats were selected for the investigation the adrenergic and cholinergic innervation of rat heart by means of histochemical demonstration of catecholamine fluorescence and acetylcholinesterase (ACHE). Consecutive method was employed on the same section to demonstration the relation between the distribution of the sympathetic and parasympathetic nerves in various parts of rat heart, e. g. atrium, ventricular myocardium, valves, epicardium, endocardium, atrioventricular node and coronary arteries. Adrenergic and cholinergic terminals innervated all parts dually. By comparing the photographs demonstrating the fluorescence CA and AChE on the same section treated by the consecutive method, we found that the location, the density and morphology of both types of nerve terminals were more like. In other words, under light microscopy the localization of both terminals can hardly be distinguished from each other. Such kind of morphological relation may strongly support the results of interaction between sympathetic and parasympathetic nervous systems in physiological and pharmacological experiments of heart.In the cardiac ganglia there are some small intense fluorescence ceils (SIF-cells) lying besides the postganglionic cholinergic cells of the parasympathetic nervous system. Both kinds of cells were shown in close contact with each other in the same section with consecutive method. This morphological relation provided an evidence that catecholamine containing SIF-cells may control and regulate the neurotransmission of parasympathetic cholinergic neurons.

OBSERVATIONS ON THE INNERVATION OF RABBIT AND RAT GASTRIC WALL BY MEANS OFHISTOCHEMICAL TECHNIQUE OF MONOAMINE FEUORESCENCE AND CHOLINESTERASE / 解剖学报

The innervation and distribution of 5-HT cells in gastric wall of rabbit and rat were studied by means of histochemical techniques of monoamine fluorescence and cholinesterase. And the morphological relation between them was investigated using the consecutive method for demonstrating the fluorescence and ChE on the same section. At the fundic gland, 5-HT cells were in contact with both the adrenergic and cholinergic axonal terminals. There are adrenergic and cholinergic terminals to innervate the gland cells of fundic gland, partial fundic gland the dual axonal terminal are identical in their localization and morphological outline. The loyer of muscle and smooth muscles surrounding the arteriole in various stomach layers were innervated by both adrenergic and cholinergic terminals, some of them are superimposed at the samelocalization. There are a lot of nsChE nerve ending network in gastric lamina propria beneath epithelium of gastric mucous membrane, it was discussed about their sensory nature in this paper.