INNERVATION AND NITRIC-OXIDE MODULATION OF MESENTERIC-ARTERIES OF THEGOLDEN-HAMSTER

Immunohistochemical and pharmacological techniques were used to examin e perivascular nerves, endothelium and the effects of inhibition of ni tric oxide synthesis on responses in mesenteric arteries/perfused mese nteric arterial beds of the Golden hamster. Frequency-dependent vasoco nstrictions to electrical field stimulation and dose-dependent vasocon strictions to noradrenaline were significantly augmented by N-G-nitro- L-arginine methyl ester (10(-5) M), an inhibitor of nitric oxide synth ase. In preparations with tone raised with methoxamine (10 mu M) dose- dependent relaxations to ATP, but not to acetylcholine, were blocked b y N-G-nitro-L-arginine methyl ester. In the presence of guanethidine ( 5 mu M) to block sympathetic neurotransmission there was no neurogenic relaxation to electrical field stimulation. Furthermore, the sensory neurotoxin capsaicin (0.05-5 nmol) did not elicit relaxation. Immunohi stochemical studies demonstrated dense plexuses of fibres immunoreacti ve for tyrosine hydroxylase and neuropeptide Y, a plexus of moderate d ensity for calcitionin gene-related peptide and an absence of fibres i mmunoreactive for substance P and vasoactive intestinal polypeptide. O f particular interest is the finding that whereas sympathetic perivasc ular nerves and nitric oxide regulate the function of hamster mesenter ic arteries, there is no apparent motor function of calcitonin gene-re lated peptide-containing sensory nerves.