Adenosine contracts the isolated rat tail artery by releasing endogenous 5-hydroxytryptamine

Adenosine (10(-4)-10(-3) M) contracted the isolated rat tail artery. This effect exhibited rapidly developing tachyphylaxis. Methysergide (10(-7) M) prevented the contractile response to adenosine and 5-hydroxytryptamine (5-HT) without affecting that to noradrenaline. Pretreatment of rats with parachlorophenylalanine (PCPA) abolished the contraction to adenosine (5 X 10(-4) M). Responses to 5-HT and noradrenaline were not significantly affected. These results indicate that the contractile response of the rat tail artery induced by adenosine is probably mediated by endogenous 5-HT.