Effects of amiloride on the neurally mediated contraction of rat mesenteric artery

The effects of amiloride on contraction evoked by perivascular nerve stimulation were studied in a ring preparation of rat mesenteric artery. The contraction evoked by nerve stimulation was abolished by tetrodotoxin or prazosin. Amiloride depressed the nerve-induced contraction concentration dependently. Noradrenaline induced a tonic contraction in the artery. Amiloride inhibited the noradrenaline-induced contraction concentration dependently. The excitatory junctional potential (e.j.p.) recorded intracellularly was abolished by tetrodotoxin. The amplitude of the e.j.p. was not altered by prazosin or amiloride. These results indicate that amiloride inhibits the perivascular nerve-mediated contraction of mesenteric artery mainly through postsynaptic adrenoceptor inhibition and not through mechanisms related to e.j.p.