Characterization of receptors mediating the actions of dopamine on an identified inhibitory motoneurone of the cockroach.
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.
Davis
J P
JP
Gatty Marine Laboratory, University of St Andrews, Fife, Scotland.
Pitman
R M
RM
D000818:Animals; D003058:Cockroaches; D004298:Dopamine / Q000378:metabolism*; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D008564:Membrane Potentials; D009046:Motor Neurons / Q000378:metabolism*; D011954:Receptors, Dopamine / Q000378:metabolism*
D015259:Dopamine Agents; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D004298:Dopamine