3H-WB 4101 binding in the rat vas deferens

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Abstract
The binding of the α-adrenoceptor antagonist ligand, 3H-WB 4101, to membranes prepared from rat vas deferens is rapid, saturable and reversible. Scatchard analyses of the data show the maximal number of binding sites (B max) to be 1.528±0.060 pmoles/g original wet tissue weight and a dissociation constant (Kd) of 0.84±0.07 nM. Hill plots of the binding data revealed that 3H-WB 4101 binds to a single population of independent sites with no cooperative interactions. The relative order of potencies of α-adrenoceptor antagonists for the inhibition of 3H-WB 4101 binding, prazosin > phentolamine > yohimbine, follows the pattern expected for the α1-type of adrenoceptors. After repeated administration of prazosin to rats (0.4 mg/kg/day for 21 days), 3H-WB 4101 binding showed a significant increase in the density of α1-andrenoceptors (122% of controls). Chronic treatment with desipramine (13.6 mg/kg/day for 22 days) resulted in a significant decrease in the number of α1-adrenoceptors (79% of controls).