Beta3-adrenoceptors in the rat sacral spinal cord and their functional relevance in micturition under normal conditions and in a model of partial urethral obstruction

Aims Beta3‐adrenoceptor selective agonists are evaluated as a new treatment for patients with lower urinary tract symptoms . It is believed that β3‐AR selective agonists exert their effects via a peripheral site of action. However, β3‐ARs have been found in brain tissue. This study examined whether β3‐ARs are present in rat sacral spinal cord, and whether there are differences in β3‐AR expression between normal and partial urethral obstruction (PUO) animals, and furthermore assessed the functional relevance of spinal β3‐ARs for micturition. Methods Thirty‐eight male Sprague–Dawley rats underwent either PUO or sham‐operation. Two weeks after operation, half of the animals were used for histomorphological analysis. Remaining animals were used for functional experiments, where a β3‐AR selective agonist, BRL 37344, was given intrathecally. Bladder function was assessed by continuous cystometry in non‐anesthetized animals before and after drug administration. Results Beta3‐ARs were found in sacral spinal cord segments with an accumulation in the ventral horn. There was a significant increase of β3‐AR expression in obstructed rats. In functional experiments obstructed rats showed increased bladder weight, micturition frequency, spontaneous activity, and bladder pressures (all P