SEROTONIN, A POTENT MODULATOR OF ARACHIDONIC-ACID TURNOVER, INTERACTION WITH GLUTAMATERGIC RECEPTOR IN BRAIN CORTEX

Brain cortex synaptoneurosomes actively incorporated [C-14]arachidonic acid (AA) into lipids. Serotonin (5-HT), at a concentration range of 10 mu M-1 mM, significantly stimulates the incorporation of AA mainly into phosphatidylinositol (PI) of brain cortex synaptoneurosomes. The stimulation rate of AA incorporation by 5-HT was the same in the prese nce and absence of lysophosphatidylinositol (LPI). However, in the abs ence of LPI some stimulation of AA uptake was also observed into phosp hatidylcholine, phosphatidylethanolamine and phosphatidic acid. Buspir one, an agonist of 5-HT1A receptor, has a similar effect on AA incorpo ration into membrane lipids as serotonin itself. Moreover, ketanserin, an antagonist of 5-HT2 receptor, also induces activation of AA incorp oration into membrane lipids. On the other hand, glutamate, in a conce ntration dependent manner, significantly inhibits AA uptake into PI an d also has some inhibitory action on AA uptake into the other lipids. Serotonin itself and the agonist of 5-HT1A receptor through the activa tion of AA turnover counteract glutamate-induced inhibition of AA upta ke into lipids of brain cortex. Our results indicated that serotonin d irectly, through the specific receptors, or indirectly, through the in teraction with glutamatergic receptors, modulates turnover and the lev el of arachidonic acid in the brain.