THE EFFECT OF COCAINE AND DESIPRAMINE ON NEURONAL UPTAKE OF [H-3] NORADRENALINE AND SENSITIVITY TO NORADRENALINE OF RAT MESENTERIC RESISTANCE ARTERIES

1. The effects of cocaine and desipramine (DMI) on neuronal uptake (up take(1)) of [H-3]-noradrenaline (NA) and isometric tension development to exogenous NA were assessed in mesenteric resistance arteries of Wi star rats. 2. Both drugs concentration-dependently inhibited [H-3]-NA uptake(1), DMI being more potent than cocaine. The maximum inhibition produced by each drug was the same as that produced by denervation wit h 6-hydroxydopamine. In denervated vessels there was no effect of coca ine on [3H]-NA uptake(1). 3. Cocaine, in the same concentration range which caused inhibition of uptake(1), increased the sensitivity to NA, while DMI, in a concentration range which inhibited uptake(1), did no t increase the sensitivity to NA and at high concentrations reduced th e sensitivity and maximal response to NA. Since DMI affected responses to NA but not responses to vasopressin and potassium its effect is pr obably related to blockade of alpha(1)-adrenoceptors. 4. We conclude t hat the effect of cocaine on the sensitivity to NA reflects inhibition of uptake(1) in rat resistance arteries, while DMI cannot be used to assess the functional effect of uptake(1) in this preparation.