ROLE OF α-ADRENERGIC RECEPTORS IN DENERVATION SUPERSENSITIVITY OF RAT VAS DEFERENS

Abstract

AbstractContractile responses of rat vas deferens were studied with particular attention directed to the role of receptors and neuronal control. Marked contraction of the vas deferens was observed with α-adrenergic agonists, depending on their concentrations. This tissue had a low sensitivity to ACh. Four days after denervation, this tissue showed a supersensitivity to α-adrenergic agonists and a high K+ concentration, but not to ACh. The increase in sensitivity to α-agonists resulted in an enhancement of the maximal response and a shift of the concentration response curve to lower concentrations of these reagents. Alterations were seen in the α-adrenergic receptors in the rat vas deferens, assayed by measuring the binding of [3H]WB4101. The maximal binding sites decreased significantly to 86 from 142 fmoles per mg protein. The affinity of the receptors for α-agonist, determined by measuring the ability of agonists to displace bound [3H] WB4101, increased significantly, while the affinity to α-antagonists remained unchanged. Studies on [3H]QNB binding indicated no significant change in muscarinic ACh receptors after denervation. Thus, supersensitivity of the α-adrenergic mechanism mediated by a specific change in affinity of α-receptors occurs after denervation of rat vas deferens. These changes in sensitivity and in receptors are discussed in relation to the characteristics and roles of α-receptors in the rat vas deferens.