title: [Dopamine-induced up-regulation of alpha 2-adrenoceptors in crude synaptic membranes of rat brain].
abstract: After cerebral cortical membranes were incubated with 0.1-100 microM of dopamine (DA) in 50 mM Tris-HCl buffer (pH 7.7) at 37 degrees C for 30 min, [3H] clonidine binding to alpha 2-receptors was increased in a concentration-dependent manner without changing [3H] WB4101 and [3H] DHA binding to alpha 1- and beta-receptors, respectively. Scatchard analysis of [3H] clonidine binding to cortical membranes showed that DA increased the Bmax in both high- and low-affinity components. The increasing effect of DA on [3H] clonidine was dependent on incubation time and temperature, and it was antagonized by pimozide and cis-flupenthixol. The addition of GTP produced a reduction in DA-induced elevation in [3H] clonidine binding, while that of cyclic AMP did not affect the effect of DA. DA and Mn2+, though both of them increased [3H] clonidine binding, appeared to act at a different site in the membrane. Furthermore, the DA-induced increase in [3H] clonidine was found uniformly in membranes prepared from 7 other regions of the rat brain. These results suggested that DA regulates specifically alpha 2-receptor density by stimulating D1-receptors and/or via other mechanism(s).
authors.forename: Y
authors.initials: Y
authors.lastname: Kohno
authors.forename: Y
authors.initials: Y
authors.lastname: Nomura
authors.forename: T
authors.initials: T
authors.lastname: Segawa
mesh_terms: D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D003000:Clonidine / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D005475:Flupenthixol / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013570:Synaptic Membranes / Q000032:analysis
chemical_list: D011942:Receptors, Adrenergic, alpha; D010868:Pimozide; D008345:Manganese; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D005475:Flupenthixol; D003000:Clonidine; D004298:Dopamine