Functional evaluation of sympathetically mediated responses in in vivo lower urinary tract of dogs.

An in vivo procedure for evaluating local effects of alpha-adrenoceptor stimuli on the lower urinary tract was developed in anesthetized dogs. Electrical stimulation of hypogastric nerve at varied frequencies (1, 2, and 4 Hz) and intraarterial (i.a.) administration of an alpha 1-adrenoceptor agonist, phenylephrine (0.3, 1, and 3 micrograms) to the urethra and bladder through the cannulated right external iliac artery caused reproducible frequency- or dose-related increases in intraurethral pressure (IUP). Intrabladder pressure (IBP) was increased by the nerve stimulation but not by i.a. phenylephrine. Acetylcholine (10 micrograms) given i.a. elicited increases in both IUP and IBP. Prazosin (0.1, 1, and 10 micrograms/kg, i.v.) dose-dependently suppressed the urethral contractile responses to the nerve stimulation and i.a. phenylephrine, but it failed to affect the bladder contraction evoked by the nerve stimulation. The results suggest that the urethral contractile responses to hypogastric nerve stimulation as well as i.a. phenylephrine were mediated via alpha 1-adrenoceptors, whereas the IBP increasing effect of hypogastric nerve stimulation was not mediated via alpha 1-adrenoceptors.