3H-WB 4101 binding in the rat vas deferens. Effects of chronic treatments with desipramine and prazosin.

1. The binding of the alpha-adrenoceptor antagonist ligand, 3H-WB 4101, to membranes prepared from rat vas deferens is rapid, saturable and reversible. 2. Scatchard analyses of the data show the maximal number of binding sites (Bmax) to be 1.528 +/- 0.060 pmoles/g original wet tissue weight and a dissociation constant (Kd) of 0.84 +/- 0.07 nM. 3. Hill plots of the binding data revealed that 3H-WB 4101 binds to a single population of independent sites with no cooperative interactions. 4. The relative order of potencies of alpha-adrenoceptor antagonists for the inhibition of 3H-WB 4101 binding, prazosin greater than phentolamine greater than yohimbine, follows the pattern expected for the alpha 1-type of adrenoceptors. 5. 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 alpha 1-adrenoceptors (122% of controls). 6. Chronic treatment with desipramine (13.6 mg/Kg/day for 22 days) resulted in a significant decrease in the number of alpha 1-adrenoceptors (79% of controls).