[Coupling of metabotropic receptors to ionic channels. Role of G-proteins]

Abstract

Besides channel receptors, there exist membrane receptors coupled to ionic channels by mean of proteins having GTPase activity. We show here as an example the dopamine receptor in the prolactin secreting cell in the anterior pituitary of the rat. The activation of D2 type receptors promotes varied effects on the electrophysiological properties of the cell membrane. They basically consist in a potassium dependent hyperpolarization and a decrease of excitability, linked to modifications of permeability of voltage-dependent potassium or calcium channels. By means of the patch-clamp technique associated to intracellular dialysis of antibodies or anti-sense oligonucleotides directed against the different G proteins alpha subunits, we have shown that the D2 receptor can activate different cellular effectors (potassium or calcium channels) by the mean of specific G proteins, thus accounting for the functional pleiotropy of the D2 receptor.