ROLE OF SPINAL AND PERIPHERAL ALPHA(2) ADRENOCEPTORS IN MICTURITION IN NORMAL CONSCIOUS RATS

Purpose: To explore the potential of alpha(2)-adrenoceptors in modulat ing 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 selecti ve alpha(2)-adrenoceptor agonist, dexmedetomidine (dex) 3 nmol., decre ased micturition pressure, bladder capacity, micturition volume and re sidual 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. Atip amezole 30 nmol. intrathecally increased micturition pressure, bladder capacity and residual urine, and decreased micturition volume. Simila r effects were obtained when atipamezole 60 nmol. was given intra-arte rially. The selective alpha(2)-adrenoceptor antagonist, rauwolscine 20 0 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.