EFFECTS OF AMILORIDE ON THE NEURALLY-MEDIATED CONTRACTION OF RAT MESENTERIC-ARTERY

The effects of amiloride on contraction evoked by perivascular nerve s timulation were studied in a ring preparation of rat mesenteric artery . The contraction evoked by nerve stimulation was abolished by tetrodo toxin or prazosin. Amiloride depressed the nerve-induced contraction c oncentration 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 amplitu de of the e.j.p. was not altered by prazosin or amiloride. These resul ts indicate that amiloride inhibits the perivascular nerve-mediated co ntraction of mesenteric artery mainly through postsynaptic adrenocepto r inhibition and not through mechanisms related to e.j.p.