Role of supraspinal and spinal α1-adrenergic receptor subtypes in micturition reflex in conscious rats

Yoshizumi M, Matsumoto-Miyai K, Yonezawa A, Kawatani M. Role of supraspinal and spinal alpha 1-adrenergic receptor subtypes in micturition reflex in conscious rats. Am J Physiol Renal Physiol 299: F785-F791, 2010. First published July 28, 2010; doi:10.1152/ajprenal.00553.2009.-alpha 1-Adrenergic receptor subtypes are widely distributed in the central nervous system and are involved in autonomic functions such as micturition. We investigated the presence and the role of supraspinal and/or spinal alpha 1-adrenergic receptors in modulating the micturition reflex in conscious female Wistar rats. The expression of alpha 1-adrenergic receptor subtypes in rat brain and lumbosacral spinal cord was studied using RT-PCR. Continuous-infusion cystometrograms were obtained in conscious rats, and alpha 1-adrenergic receptor antagonists were administered via intracerebroventricular or intrathecal routes. The mRNA expression of alpha(1A)-, alpha(1B)-, and alpha(1D)-adrenergic receptors was detected in rat brain (midbrain and pons) and lumbosacral spinal cord (dorsal and ventral parts of spinal cord). In addition, intracerebroventricular injection of the alpha 1-adrenergic receptor antagonist tamsulosin (1-10 mu g), the selective alpha(1A)-adrenergic receptor antagonist silodosin (1-10 mu g), and the selective alpha(1D)-adrenergic receptor antagonist BMY 7378 (1-10 mu g) significantly prolonged the intercontraction interval (ICI) but did not alter maximum voiding pressure (MVP). Although intrathecal injection of BMY 7378 (0.0001-10 mu g) did not affect ICI, tamsulosin and silodosin prolonged ICI in a dose-dependent manner. MVP was significantly reduced by intrathecal injection of tamsulosin (10 mu g) but not by silodosin or BMY 7378 (0.0001-10 mu g). Supraspinal alpha(1A)- and alpha(1D)-adrenergic receptors are apparently important for the regulation of reflex-bladder activity in conscious rats. Noradrenergic projection from the brain stem to the lumbosacral spinal cord may promote the afferent limb rather than the efferent limb of the micturition reflex pathway via alpha(1A)-adrenergic receptors.