Abstract
Effects of testosterone on the autonomic receptor-mediated function of the male rabbit urinary bladder and proximal urethra were examined. The alteration of α1-, α2-, β-adrenergic receptor and muscarinic cholinergic receptor densities in the urinary bladder and proximal urethra were determined by radioligand binding techniques after castration. The density of α1-adrenergic receptor in the proximal urethra decreased gradually after castration. This change was significant 8 weeks after castration. The α2-adrenergic receptor density in the proximal urethra slightly increased after castration, but it was not statistically significant. The β-adrenergic receptor density in the bladder dome did not change after castration. The density of muscarinic cholinergic receptor in the bladder dome significantly decreased in animals 2 weeks after castration. Additionaly, the density of autonomic receptors and the response of muscle strips to autonomic drugs were compared in three age-matched experimental groups: control group, castrated group and castrated and testosterone supplemented group. When the autonomic receptor densities in the castrated group were compared to those of the control, the changes similar to the result in the previous experiment were noted.
Testosterone supplementation restored the densities of α1-adrenergic and muscarinic cholinergic receptors in castrated group to control levels. The responses of muscle strips to autonomic drugs closely paralleled the receptor densities. Castration decreased the α1-adrenergic and the muscarinic cholinergic receptor function, however, testosterone restored those function. These findings indicate that testosterone affects the autonomic receptor-mediated function in the smooth muscle of lower urinary tract.
