Butanol extracts from myelin fragments-II. Some properties of 5-hydroxytryptamine binding

The myelin fragments of rat brain stem were treated with butanol-water mixtures, and the butanol extracts (total extract=TE) were incubated with 5 x10(-7) M of C14.5-HT. After incubation, protein, lipid phosphorus and radioactivity were analyzed by Sephadex LH20 column chromatography. Two peaks of components eluted in chloroform-methanol 4:1 (peak I and II) showed the binding capacity for C14.5-HT. The displacement studies with unlabeled 5-HT (5 X 10(-4) M) suggested that peak II was the saturable binding component to 5-HT. On the other hand, butanol extracts from the synaptic membranes of rat brain stem did not show binding for C14.5-HT. Various compounds were studied to determine their inhibitory effects on the saturable binding of 5-HT to TE. The results indicated that acetylcholine, dopamine and tryptamine inhibited the 5-HT binding but LSD, reserpine, colchicine, vinblastine, 5-hydroxytryptophan (5-HTP) and 5-hydroxy-3-indole acetic acid (5-HIAA) had no effect.