DOPAMINERGIC RECEPTORS IN HYDRA - PHARMACOLOGICAL AND BIOCHEMICAL OBSERVATIONS

1. The dopaminergic receptors of Hydra have been studied by pharmacological and biochemical methods. 2. D1 selective agonists, D2 selective agonists and D1-D2 mixed-action agonists inhibit the glutathione-induced feeding response. 3. Dopaminergic blocking agents protract the glutathione action, regardless of their D1 or D2 selectivity. 4. A very long-lasting response is observed in 6-hydroxydopamine-treated specimens. 5. H Hydra treatment with dopamine agonists (D1, D2 or mixed-action) induces a significant rise in cAMP levels. 6. Pretreatment with blocking agents prevents both the enhancement of cyclic nucleotide levels and the inhibition of feeding response induced by dopaminergic agonists, regardless of their D1 or D2 selectivity.