INVESTIGATION OF WHETHER SEPTAL GAMMA-AMINOBUTYRATE-CONTAINING INTERNEURONS ARE INVOLVED IN THE REDUCTION IN THE TURNOVER RATE OF ACETYLCHOLINE ELICITED BY SUBSTANCE-P AND BETA-ENDORPHIN IN THE HIPPOCAMPUS

Afferents to the septum that contain substance P or β-endorphin probably have an inhibitory action upon the acetylcholine metabolism of the cholinergic septohippocampal pathway because intraseptal administration of these peptides decreases the turnover rate of acetylcholine in the hippocampus. Bicuculline, an antagonist of γ-aminobutyric acid, blocks the inhibitory action of β-endorphin on acetylcholine turnover suggesting that it is mediated via the septal γ-aminobutyric acid-containing interneurons. Inhibition by substance P of the turnover of acetycholine in the hippocampus is independent of this type of interneuron. Dopamine, like β-endorphin, acts on γ-aminobutyrie acid-containing interneurons of the septum. However, lesions of dopaminergic cell bodies located in area A10 have established that the dopaminergie and β-endorphin-containing inputs to the septal γ-aminobutyric acidcontaining interneurons are independent of each other. © 1979.