Characterization of autonomic receptors in neonatal urinary tract smooth muscle.

In the 1-day-old rabbit there are a large number of alpha-2- (labeled with [3H]yohimbine) than alpha-1- (labeled with [3H]prazosin) adrenergic receptors in the various parts of urinary tract smooth muscle, but the alpha-1 receptors are functionally more responsive to agonists than are the alpha-2 receptors. Unlike the findings in the adult rabbit, the neonatal bladder dome is functionally more sensitive to alpha-adrenergic agonists than the neonatal bladder base. The rank order of beta-adrenergic receptor densities (labeled with [3H]dihydroalprenolol) in various urinary tract smooth muscles correlates with the magnitude of the relaxant response to isoproterenol. There is a high number of functional muscarinic receptors (labeled with [3H]quinuclidinyl benzylate) in the neonatal urinary tract. The data demonstrate the existence of functional autonomic receptors in neonatal urinary tract smooth muscle.