IN-VITRO EFFECTS OF ARACHIDONIC AND L-GLUTAMIC ACIDS ON THE HIGH-AFFINITY CHOLINE TRANSPORT IN RAT HIPPOCAMPUS

A second messenger role for arachidonic acid (AA) in the regulation of the high-affinity choline uptake (HACU) was suggested. It was reporte d that micromolar concentrations of AA applied in vitro decreased the HACU values and increased the specific binding of [H-3]hemicholinium-3 ([H-3]HCh-3). It was published that L-glutamic acid (GA) applied in v ivo produced a fall in the HACU values. In addition, GA liberates free AA. In this study, an ability of GA to influence in vitro the activit y of presynaptic cholinergic nerve terminals via its effect on the rel ease of AA is investigated in hippocampal synaptosomes of young Wistar rats. Millimolar concentrations of GA decrease both the high- and low -affinity choline uptake, the specific as well as nonspecific binding of [H-3]HCh-3 and the activity of Na+,K+-ATPase. Kinetic analysis (Lin eweaver-Burk and Scatchard plots) reveals a change in V-max and B-max, but not in K-M and K-D. It appears very likely that under normal cond itions GA applied in vitro is not able to change markedly the choline transport via its effect on the release of AA. Results confirm the hyp othesis about an indirect inhibitory role for glutamatergic receptors on cholinergic cells.