EFFECTS OF DESIPRAMINE ON NEURONAL RESPONSES TO DOPAMINE, NORADRENALINE, 5‐HYDROXYTRYPTAMINE AND ACETYLCHOLINE IN THE CAUDATE NUCLEUS OF THE RAT

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Abstract
The sensitivity of single neurones to microelectrophoretically applied dopamine, noradrenaline (NA), 5‐hydroxytryptamine (5‐HT) and acetylcholine (ACh) was investigated in the caudate nucleus of the rat, anaesthetized with halothane. Both excitatory and depressant responses could be observed to each of the agonists. There was a high correlation between the direction of responses to dopamine and noradrenaline, whereas there was no significant correlation between the direction of responses to dopamine and ACh. The effect of desipramine was studied on both excitatory and depressant responses to dopamine, NA and 5‐HT, and on excitatory responses to ACh. Both potentiation and antagonism of neuronal responses to monoamines and ACh could be observed after a brief application of desipramine. Excitatory responses to glutamate were not affected by desipramine. The observation that responses to dopamine and NA can be potentiated by desipramine in the caudate nucleus suggests that uptake blockade is not a prerequisite for potentiation. It is suggested that the potentiation of neuronal responses to dopamine by desipramine may be responsible for the therapeutic efficacy of desipramine in Parkinson's disease.