A pharmacological study of dopaminergic receptors in planaria.

The dopaminergic receptors of planaria have been studied with pharmacological and biochemical criteria. Dopamine D1 selective agonists (CY 208243 (10 micrograms/ml) and SKF 38393 (10 micrograms/ml] induced in planaria typical screw-like hyperkinesias, that were inhibited by a D1 antagonist (SCH 23390 (10 micrograms/ml], but not by a D2 antagonist (sulpiride (1000 micrograms/ml]. Dopamine D2 selective agonists (PHNO (5 micrograms/ml), lisuride (5 micrograms/ml] on the contrary induced a typical "C" like curling, that was inhibited by pretreatment with D2 selective blocking agents, but not by D1 selective blocking agents. With agonists with a D1/D2 mixed action (apomorphine 60 micrograms/ml) or with amphetamine (100 micrograms/ml), the D1 type movements appeared to be more evident. Dopamine D1-selective agonists, mixed action agonists or D2-selective agonists, all induced a significant increase in levels of cAMP, that was prevented by pretreatment with the specific DA blocking agent.