Abstract

Slow filling (0.03 ml/min) to 25 cm H2O transluminal hydrostatic pressure established an internal volume ("end-filling volume"; V) in rat seminal vesicles which was optimal for the production of maximal isovolumetric contractions. Because of variations in the size and empty wet weight (W) of vesicles from mature rats, this method for standardizing base-line conditions was superior to the application of a standard volume to preload all organs. The slow-filling procedure to establish base-line conditions yielded a parameter (V/W) which was an index of organ distensibility; therefore, both mechanical and pharmacological properties could be related in each organ. V/W was reasonably constant and independent of organ weight; regression analysis showed K = V/W3/4. Pretreatment of animals with 6-hydroxydopamine. HBr (100 mg/kg 2 weeks, plus 50 mg/kg 1 week, before sacrifice) and surgical postganglionic denervation (9 to 12 days before sacrifice) significantly increased V/W, had no effect on W and resulted in a 40% increase in the maximum response to norepinephrine. The EC50 of norepinephrine was slightly increased after 6-hydroxydopamine-pretreatment. Short-term reserpine-pretreatment (5 mg/kg 2 days plus 2.5 mg/kg 1 day, before sacrifice) produces better norepinephrine depletion than 6-hydroxydopamine but did not modify V/W. The results suggest that the stress-strain relationship and elastic properties of sympathetically innervated tissues are subject to the long-term influence of nerve activity.