Studies on membrane receptor sites for serotonin in the brain

The competitive effect of 5,6-dihydroxytryptamine, morphine and chlorpromazine on the binding of serotonin (5-HT) to rat brain slices was investigated. Ths busynaptosomal localization of the binding of morphine in bovine midbrain preparations was compared to that of 5-HT and found to be considerably higher. The condensation of 5-HT and tryptamine receptor carbonyl groups in brain with phenylisopropylhydrazine was shown in vitro and vivo. Membrane particles labeled with [14C] tryptamine or 5-HT in presence or absence of sodium borohydride (NaBH4) were extracted with chloroform-methanol (C-M) 2:1. The labeled proteolipid precipitated by ether from these extracts showed on electropherograms one single radioautographic spot which was more intense with samples treated with sodium borohydride. In column chromatography, the bound radioactivity peak eluted with the gel void volume, was associated with a protein peak. The eluted, lyophilized material of this fraction was extracted by chloroform methanol (2:1) thus suggesting its proteo-lipid nature.