Guanine nucleotides and pertussis toxin alter agonist binding to rat septal V(1)-vasopressin receptors.
To investigate whether the rat brain vasopressin receptor is coupled to phospholipase C by a GTP-binding protein, the effects of guanine nucleotides and pertussis toxin on agonist binding to septal membranes were examined. Synaptic plasma membranes were prepared from rat septal tissue and binding of [(3)H]AVP was examined in the presence of guanine nucleotides at a concentration of 1 mM. Saturation isotherms revealed that all guanine nucleotides significantly increased the dissociation constant K(d), and the nonhydrolyzable GTP analogs GTPgammaS and Gpp(NH)p had the most pronounced effect. Treatment of membranes with pertussis toxin reduced the specific binding of 2 nM [(3)H]AVP by over 50%. These data suggest that the septal vasopressin receptor is coupled to phospholipase C via a G(i)- or G(o)-like GTP-binding protein.
Swank
M W
MW
Geriatric Research Education, and Clinical Center, Veterans Aljairs Medical Center, Seattle, Washington 98108, USA; Department of Psychology, Physiology and Biophysics, Pharmacology, and Medicine, University Washington School of Medicine, Seattle, Washington 98195, USA.
Dorsa
D M
DM