Role of spinal and peripheral alpha(2) adrenoceptors in micturition in normal conscious rats

Purpose: To explore the potential of alpha(2)-adrenoceptors in modulating vesicourethral function at the spinal and bladder levels. Material and Methods: Continuous cystometry was performed in normal, conscious rats, and the urodynamic effects of alpha(2)-adrenoceptor stimulation and blockade were recorded. Results: Given intrathecally, the selective alpha(2)-adrenoceptor agonist, dexmedetomidine (dex) 3 nmol., decreased micturition pressure, bladder capacity, micturition volume and residual volume. These effects were counteracted by the selective alpha(2)-adrenoceptor antagonist, atipamezole 30 nmol. Intrathecally dex 10 nmol. caused total incontinence in 9 of 9 rats. Given intra-arterially near the bladder, dex 6 nmol. decreased micturition pressure, bladder capacity, micturition volume, residual urine and basal pressure. Atipamezole 30 nmol. intrathecally increased micturition pressure, bladder capacity and residual urine, and decreased micturition volume. Similar effects were obtained when atipamezole 60 nmol. was given intra-arterially. The selective alpha(2)-adrenoceptor antagonist, rauwolscine 200 nmol., had effects similar to those of atipamezole. Conclusions: The results show that alpha(2)-adrenoceptors can modulate micturition in normal conscious rats both at the spinal and the peripheral levels.