The ontogeny of the autonomic innervation and contractile response of the rabbit urinary bladder

Although there has been considerable research on urinary bladder innervation, physiology and response to pharmacological agent, very little information is available concerning the ontogeny of bladder innervation and the contractile response to autonomic agents. The developmental aspects of urinary bladder innervation and function have been studied in the rabbit utilizing the following techniques: histochemical methodology to demonstrate autonomic innervation; in vitro responses to autonomic agents to demonstrate contractile responses; and ratio-ligand binding assays to determine specific receptor densities. The results of these studies can be summarized as follows: 1) at birth, the density of adrenergic fibers in the rabbit urinary bladder is very sparse, whereas there is a dense cholinergic innervation present. Over the first 6 weeks of postnatal development, there is a rapid progressive increase in the density of adrenergic fibers, whereas there is no significant change in the cholinergic innervation; 2) at birth, isolated strips of bladder respond poorly to methoxamine (alpha adrenergic agonist) and isoproterenol (beta-adrenergic agonist), but well to bethanechol (muscarinic cholinergic) and ATP (purinergic); 3) at birth, the density of adrenergic alpha and beta receptors is low; over the first 6 weeks of postnatal development, the density increases progressively to adult levels. The muscarinic receptor density is high at birth and does not change significantly over the first 6 weeks of postnatal development.