Effect of postganglionic denervation and pretreatment with reserpine on alpha-adrenoceptors of the guinea-pig vas deferens.

The radiolabeled alpha-1-adrenoceptor antagonist [3H]WB-4101 was used to determine whether supersensitivity of the guinea pig vas deferens that develops after denervation or reserpine pretreatment is associated with a change in the characteristics of the alpha-1-adrenoceptor. Specific binding of [3H]WB-4101 to membrane fractions of vasa deferentia was saturable and reversible. The dissociation constant (KD) was similar when obtained by equilibrium or kinetic studies. As determined by Scatchard analysis, neither chronic (5 days) pretreatment with reserpine (1.0 mg/kg/day) nor postganglionic denervation (7 days) altered the number or affinity of [3H] WB-4101 binding sites. It is concluded that changes in alpha-1-receptor characteristics are not responsible for postjunctional supersensitivity in this tissue.