Presynaptic cholinergic action in the hippocampus.
The hippocampus is among the regions in the brain richest in M1 cholinergic receptors. Topical application of acetylcholine (ACh) onto hippocampal slices produces a characteristic complex response consisting of a depolarization, an increase in input resistance especially upon depolarization and a blockade of a slow afterhyperpolarization (AHP). The first two of these responses can be recorded also in non-cholinergic septal neurons in an area which contains about 8% of the M1 muscarinic receptors found in the hippocampus. The responses of hippocampal but not septal neurons to ACh involve an increase in the spontaneous synaptic activity and a decrease in evoked responses to afferent stimulation. The dissociated hippocampal culture was used to study these presynaptic effects. The neurons in culture possess muscarinic receptors which develop gradually over a period of several weeks after plating. ACh rarely depolarizes hippocampal neurons in culture. Instead, it causes an increase in spontaneous discharge of small postsynaptic currents (PSC's) and a marked decrease of large, evoked PSC's. In some cultured hippocampal cells ACh reduced ICa without affecting any of several outward K currents studied. It is suggested that ACh reduces evoked activity by reducing Ca currents at presynaptic terminals.
Segal
M
M
Center for Neurosciences, Weizmann Institute of Science, Rehovot, Israel.
Greenberger
V
V
Markram
H
H
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D014298:Trimethyltin Compounds / Q000494:pharmacology
D014298:Trimethyltin Compounds; C046488:trimethyltin; D000109:Acetylcholine