Effects of electrical stimulation on acetylcholine levels in central cholinergic nerve terminals

Abstract

These studies explored some of the characteristics of the cholinergic septal-hippocampal neurons. Acetylcholine (Ach) levels were measured after various conditions of electrical stimulation of the medial septal area. Stimulation (40 Hz) for varying periods of duration up to 60 min did not alter hippocampal Ach levels. However, when 10 μg of hemicholinium-3 bromide (HC-3) were injected into the lateral ventricles immediately prior to stimulation, there was a maximal 50% depletion of Ach levels after 7.5 min of stimulation. There was no significant depletion of Ach when 1 or 5 μg of HC-3 was utilized, and there was no further depletion (beyond that observed with 10 μg) when 15 or 20 μg were injected. In experiments where the stimulation frequencies were varied, it was observed that 0.4 and 1 Hz did not lower Ach levels, whereas frequencies between 10 and 100 Hz resulted in a similar 50% depletion at 7.5 min. Three days after cessation of stimulation (40 Hz, 10 μg HC-3), Ach levels had returned to that of untreated controls. Stimulation of the corpus striatum did not have any effect on hippocampal Ach levels.