The mean volume of saline (infused at a physiological-like rate) required to elicit neurogenic rhythmic contractions of the detrusor muscle (micturition threshold) in urethane anasthetized rats was reduced by reserpine pretreatment, as welf as by chemicaf (6hydroxydopamine) OF surgical sympathectamy (bilateral section of the hypogastric nerves). Propranolol pretreatment had no significant effect on micturition threshold but increased the β¬n~ralu~ninal pressure at which the rhythmic contractions occurred. In spinal rats fT12-LI) a flat pressure volume curve was obtained with only a minor phasic contractile activity. Propranolol administration or bilateral section of the hypogastric nerves significantly increased the intraluminal pressure response to saline filling in spinal rats. Topical tetrodotoxin increased the intrafuminaf pressure response to saline titling in control spinal rats but not fobwing propranolol administration or bilateral section of the hypogastric nerves.
These findings provide evidence for a sympathetic inhibition of the reflex activation of the detmsor muscle in response to a ~hysiologica~-i~ke fifling of the urinary bladder.