Role of spinal alpha1-adrenoceptor subtypes in the bladder reflex in anesthetized rats.
The contribution of different subtypes of alpha1-adrenoceptors in the lumbosacral spinal cord to the control of the urinary bladder was examined in urethane-anesthetized rats. Bladder pressure was recorded via a transurethral catheter under isovolumetric conditions. Drugs were administered intrathecally at the L6-S1 segmental level of spinal cord. RS-100329 (an alpha1A-antagonist) in doses of 25, 50, and 100 nmol significantly decreased bladder-contraction amplitude by 38%, 52%, and 95%, respectively, whereas (+)-cyclazosin (an alpha1B-antagonist) significantly decreased bladder-contraction amplitude (48% reduction) only in a 50-nmol but not a 100-nmol dose. Fifty nanomoles of RS-100329 and (+)-cyclazosin increased bladder-contraction frequency by 54% and 44%, respectively. BMY7378 (an alpha1D-antagonist), in doses of 25, 50, and 100 nmol, did not change bladder activity. These studies suggest that reflex-bladder activity is modulated by two types of spinal alpha1-adrenergic mechanisms: 1) alpha1A- or alpha1B-inhibitory control of the frequency of voiding reflexes presumably mediated by an alteration in the processing of bladder afferent input and 2) alpha(1A)-facilitatory modulation of the descending efferent limb of the micturition-reflex pathway. Spinal alpha1D-adrenoceptors do not appear to have a significant role at either site.
Yoshiyama
M
M
Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261, USA. PXN15164@nifty.ne.jp
De Groat
W C
WC
D000768:Anesthesia, General; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology; D005260:Female; D007278:Injections, Spinal; D008125:Locus Coeruleus / Q000502:physiology; D008959:Models, Neurological; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology; D011312:Pressure; D011799:Quinazolines / Q000008:administration & dosage / Q000494:pharmacology; D011810:Quinoxalines / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013941:Thymine / Q000008:administration & dosage / Q000502:physiology; D014520:Urethane; D001743:Urinary Bladder / Q000294:innervation*
D010879:Piperazines; D011799:Quinazolines; D011810:Quinoxalines; C120711:RS 100329; D018340:Receptors, Adrenergic, alpha-1; C080462:cyclazosin; D014520:Urethane; C053428:BMY 7378; D013941:Thymine