Contraction and relaxation of rabbit basilar artery by thiopental

Tension measurements were made on rabbit basilar artery segments to test the direct effect of thiopental on serotonin (5HT)- and norepinephrine (NE)-induced contraction. At concentrations of 3 X 10(-5) M or greater, thiopental caused relaxation of NE-induced tension. Thiopental doses greater than 3 X 10(-4) M had a similar relaxing effect on 5HT-induced contraction. However, thiopental doses below 3 X 10(-4) M demonstrated an unexpected dose-dependent potentiation of the 5HT-induced contraction.