Action of detergents on 3H-dihydroergokriptine binding and localization of alpha-adrenoceptors in synaptosomal membranes.
3H-dihydroergokriptine (3H-DHE) binding was carried out in synaptosomal membranes from basal ganglia of the cat. A single type of binding site with Kd 3.7 nM, Hill number = 0.95 and Bmax = 1000 pmol/g protein was found. 3H-DHE bound to alpha-adrenoceptors and not to serotonin or dopamine receptors. At very low concentrations, some detergents enhanced binding, but at higher concentrations of those used (Triton X-100, Nonidet P-40, deoxycholate and digitonin), inhibited the binding of 3H-DHE. After binding to the membrane protein, the 3H-DHE-receptor complex was stable to the action of Triton X-100. At concentrations of Triton X-100. At concentrations of Triton X-100 (0.1--0.2%). in which only the presynaptic membrane disintegrated, the 3H-HDE specific radioactivity was reduced. With a more drastic treatment that disintegrated the postsynaptic membrane, 3H-DHE binding was further reduced. These results suggest that alpha-adrenergic receptors may be localized at both the pre- and postsynaptic membranes of central synapses.
D000818:Animals; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D002415:Cats; D003902:Detergents / Q000494:pharmacology*; D004088:Dihydroergotoxine / Q000378:metabolism*; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D003902:Detergents; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D011092:Polyethylene Glycols