| RESEARCH PAPER
|Year : 1981 | Volume
| Issue : 3 | Page : 233-243
Mechanism of action of 5-hydroxytryptamine on the rat anococcygeus muscle
RK Goyal, NM Patel, SC Verma
5-Hydroxytryptamine (5 HT), produced dose-dependent cotraction in the rat anococcygeus muscle. Cyproheptadine (1 x 10-6M), a specific 5HT receptor blocker failed to inhibit the responses to 5HT. However phentolamine (1 x l0-6M), a specific ( receptor blocker produced competitive antagonism (PA2 = 8.3) with 5HT. Responses to SHT were also inhibited in the reserpinised (5 mg/kg ip, 24 h before) and 6-hydroxy dopamine (60HDA) pretreated preparations. Repeated doses of 5HT produced tachyphylaxis.Imipramine, a 5HT uptake blocker, produced non-competitive inhibition of the responses to 5HT (pD'2 = 7.73(0.1). Nialamide, a MAO inhibitor and pyrogallol, a COMT inhibitor, significantly potentiated the responses to 5HT. However the combined effect of tyramine and 5HT responses were not additive. Our data suggest an indirect effect of 5HT in rat anococcygeus muscles. Further more the mechanism of release appears to be tyramine-like.
R K Goyal
Source of Support: None, Conflict of Interest: None