Hemicholinium impairs septo-hippocampal facilitatory action.
Intraventricular injections of hemicholinium-3 led to a sharp reduction in hippocampal acetylcholine content (by 79% on the average). This was associated with the following changes in population spikes evoked in area CA1 by commissural stimulation: (1) a tendency to progressive increase, over 1-2 hours; (2) in a few cases (3 out of 12), a striking depression of the normal strong facilitation produced by brief tetanic stimulation of the medial septum (typically 10 pulses at 50-100 Hz); (3) a much more consistent tendency towards fading of the septal facilitatory effect during repeated applications of such brief septal tetani (in 10 cases out of 12); as well as, (4) diminished facilitation by sustained, lower frequency septal tetanic stimulation (20-50 Hz). The reduced efficiency of septal action--especially during repetitive stimulation--was not accompanied by a consistent reduction of the facilitation produced by local applications of acetylcholine; it is, therefore, best explained by the diminished availability of acetylcholine, and so provides further evidence that septo-hippocampal facilitation is mediated by a cholinergic mechanism.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D006426:Hemicholinium 3 / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects*; D009434:Neural Pathways / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012686:Septal Nuclei / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D006426:Hemicholinium 3; D000109:Acetylcholine