COUPLING OF METABOTROPIC RECEPTORS TO ION IC CHANNELS - THE ROLE OF G-PROTEINS

Besides channel receptors, there exist membrane receptors coupled to i onic channels by mean of proteins having GTPase activity. We show here as an example the dopamine receptor in the prolactin secreting cell i n the anterior pituitary of the rat. The activation of D2 type recepto rs promotes varied effects on the electrophysiological properties of t he cell membrane. They basically consist in a potassium dependent hype rpolarization 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 dialys is of antibodies or anti-sense oligonucleotides directed against the d ifferent G proteins alpha subunits, we have shown that the D2 receptor can activate different cellular effectors (potassium or calcium chann els) by the mean of specific G proteins, thus accounting for the funct ional pleiotropy of the D2 receptor.