Effects of cocaine or denervation on responses of isolated strips of cat spleen to (-)-noradrenaline and (-)-isoprenaline.

1. A study has been made of the effects of cocaine and sympathetic denervation on responses of the cat spleen to (-)-noradrenaline and (-)-isoprenaline.2. Responses of isolated strips of spleen capsule to (-)-noradrenaline or to (-)-isoprenaline were not affected by reserpine-pretreatment.3. In adult cats, cocaine (1 and 10 mug/ml) or denervation produced a shift to the left of dose-response curves to (-)-noradrenaline, whereas they failed to modify dose-response curves to (-)-isoprenaline.4. There was an increase in the maximum development of tension to (-)-noradrenaline after denervation or in the presence of cocaine (10 mug/ml). These procedures did not increase the maximal responses to (-)-isoprenaline.5. Cocaine (10 mug/ml) did not affect dose-response curves to (-)-noradrenaline or (-)-isoprenaline in the denervated spleen.6. In the kitten spleen, cocaine (1 and 10 mug/ml) produced a shift to the left of dose-response curves to (-)-noradrenaline both in untreated and in reserpine-pretreated tissues.7. There was a small shift to the left in dose-response curves to (-)-isoprenaline in the presence of cocaine in the untreated but not in the reserpine-pretreated kitten spleen.8. It is concluded that the potentiation of responses to (-)-noradrenaline in the cat's spleen is due to a prejunctional effect of cocaine.