[3H]5-HT binding sites and 5-HT-sensitive adenylate cyclase in glial cell membrane fraction.
Glial cell membrane fractions were prepared using glial cells preparations isolated from horse brain striatum. [3H]5-HT binding was measured by the filtration technique and the adenylate cyclase activity determined by measuring the cAMP production using a radioimmunoassay. Serotonin binds to glial membrane fractions with an affinity corresponding to a dissociation constant Kd = nM. The corresponding site is serotoninergic specific: [3H]5-HT binding is inhibited by 5-HT agonists (5 OH NM-DMT, 5-MeOHT, 5-MeOH-DMT, NN-DMT) or antagonists (cinanserine, cyproheptadine, methysergide, LSD) and not (or poorly) inhibited by non-serotoninergic related drugs. The population of sites binding 5-HT, present in neuronal membrane preparations and determined in parallel assays is distinct from that observed in glial preparations. The glial membrane fractions contains an adenylate cyclase activated by 5-HT with an apparent affinity constant close to 1 microM. It is serotonin-specific and clearly distinct from the DA-stimulated adenylate cyclase present in the same preparation. The sites binding 5-HT and activating the adenylate cyclase with low affinities might be directly related. This system, clearly distinct from the postsynaptosomal serotoninergic receptor, represents presumably a glial serotoninergic receptor; however, it cannot be totally excluded that these sites may refer to presynaptic membranes.
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000187:drug effects*; D003342:Corpus Striatum / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006736:Horses; D009457:Neuroglia / Q000187:drug effects*; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects
D011985:Receptors, Serotonin; D012701:Serotonin; D000262:Adenylyl Cyclases