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Journal of Experimental Biology, Vol 155, Issue 1 203-217, Copyright © 1991 by Company of Biologists

JOURNAL ARTICLES

Characterization of receptors mediating the actions of dopamine on an identified inhibitory motoneurone of the cockroach

JP Davis and RM Pitman
Gatty Marine Laboratory, University of St Andrews, Fife, Scotland.

1. The effects of a number of dopaminergic agonists and antagonists upon the soma of a prothoracic inhibitory motoneurone of the cockroach (Periplaneta americana) have been recorded under voltage-clamp conditions. 2. Dopamine generates inward currents that are extremely voltage-dependent: currents increase rapidly at membrane potentials more negative than about -120 to -150 mV and also show a peak at membrane potentials of approximately -20 mV. As a result of this voltage-dependence, dopamine induces a region of negative resistance in the current-voltage relationship of the neurone. 3. The dopaminergic agonists apomorphine, bromocriptine, ergometrine and A-6,7-DTN mimic the action of dopamine on this neurone, all having a similar voltage-dependence to that of dopamine. The selective D-1 receptor agonist SK&F82526 and the D-2 agonist LY 171555, however, were both inactive on the preparation. 4. Responses to dopamine were suppressed by a number of D-1 and D-2 receptor antagonists, indicating that the pharmacological profile of the dopamine-sensitive receptor in this insect preparation is different from that of vertebrate dopamine receptors.




© The Company of Biologists Ltd 1991