THE BINDING OF 5‐HYDROXYTRYPTAMINE TO ACIDIC LIPIDS IN ISOBUTANOL

Abstract— In order to examine the possibility that acidic lipids can account for the binding of 5‐hydroxy [³H]tryptamine (5‐HT) to brain tissue, the binding to six acidic lipids was studied using an isobutanol‐water partition method. With the exception of the polyphosphoinositides, all the acidic lipids examined bind saturably and with high affinity. The apparent dissociation constants of 5‐HT to the acidic lipids were as follows: phosphatidylserine, 0.4 μM; phosphatidic acid, 0.6μM; diphosphoinositide, 0.8 μM; cerebroside sulfate, 1.4 μM; monophosphoinositide, 1.9 μM; and triphosphoinositide, 10 μM. The high affinity of these lipids to 5‐HT raises the possibility of some role for them in serotonergic activity.