GTP-dependent dopamine reception in central nervous system tissue of the pond snail Lymnaea stagnalis

The guanosine-5′-triphosphate (GTP) binding of D1-dopamine (DA) receptor agonist [H3]-SKF 38393 is described. The binding of [H3]-SKF 38393 occurs in two different DA receptors in the presence of guanylyl nucleotides, and in one receptor population in the absence of guanylyl nucleotides. It was shown with GDP-α-P33 binding analysis that G proteins in the mollusc nervous tissue membranes accelerate exchange of guanosine-5′-diphosphate (GDP) for GTP considerably. While binding of [H3]-SKF 38393 was not found with phosphorylation of the membranes by the catalytic subunit of cAMP-dependent protein kinase A, basal and DA-induced GDP ↔ GTP exchange was noticeably inhibited with phosphylation in the nervous tissue membranes.