CNS-mediated influence of TRH and its analog, NS-3, on the function of the rabbit lower urinary tract

The effects of thyrotropin-releasing hormone (TRH) and its new analog, NS-3 (montireline), on the lower urinary tract in rabbits were investigated. TRH and NS-3 elicited transient increases in intravesical pressure and micturition. They also caused long-lasting increases in intraurethral pressure and EMG activity of the external urethral sphincter, which were not affected by prazosin or transection of the hypogastric nerve, but were eliminated by transection of the pudendal nerve. In animals decerebrated at the supracollicular post-mammillary level, these drugs did not increase intravesical pressure or micturition, but they did elicit increases in intraurethral pressure and sphincter EMG activity. No binding sites for TRH were found in the lower urinary tract. These findings suggest that the sites of action of TRH and NS-3 which elicit intravesical pressure increase or micturition might be located in the area rostral to the pons, and that the sites of action which elicit increases in intraurethral pressure and sphincter EMG activity might be located caudal to the rostral pons.