IDENTIFICATION OF 5‐HYDROXYTRYPTAMINE BINDING SUBSTANCES FROM RAT BRAIN STEM

Abstract— Godwin & Sneddon (1975) reported the binding of 5‐hydroxy‐[³H]tryptamine (5‐HT) on a Sephadex LH‐20 column to‘proteolipid material’extracted with n‐butanol from rat brain stem. An examination of this‘proteolipid material’with TLC showed the main constituents to be cerebroside sulfate (CS), monophosphoinositide (PI), and diphosphoinositide. The elution profiles of [³H]5‐HT incubated with purified CS or with a mixture of CS and PI were similar to that of the brain extract on the same column. Because the elution profile of the mixture of CS and PI was more similar to that of the brain extract, it was concluded that what was suggested to be a possible proteolipid‘5‐HT receptor’was mainly two acidic lipids. The elution profile of [³H]5‐HT incubated with purified PI, however, was similar to [³H]5‐HT eluted alone. This suggested that either PI did not bind to 5‐HT or that the PI‐5‐HT complex possesses different Chromatographie behavior than PI. To test this latter possibility, [¹⁴C]5‐HT and [³H]PI were incubated then eluted on a Sephadex LH‐20 column with a continuous gradient of increasing polarity. The gradient first eluted PI, then an apparent PI‐5‐HT complex, and finally 5‐HT. This demonstrated that PI will bind to 5‐HT on a Sephadex LH‐20 column and that the PI‐5‐HT complex is probably more polar than PI.