Disinhibitory action of acetylcholine in the rat's hippocampus: Extracellular observations

摘要: Abstract In rats under urethane anaesthesia, fimbrial-commissural stimulation at a frequency of 1 Hz or less evoked only positive field in the pyramidal layer CA1 (and uppermost region CA3). Stimulation intensities 3–5 times threshold and frequencies 2 more led to appearance large negative population spikes. When acetylcholine was released from micropipette (10–100 nA), reduced spikes appeared, even lowest (below Hz). Known antagonists γ-aminobutyrate (bicuculline, picrotoxin penicillin) had comparable effect, but with slower time course—the action consistently very rapid onset offset (within 5 s). Population were not by when accompanying fimbrial strong enough generate higher (2 Hz), outside narrow zone where fields are recorded; nor they release glutamate instead acetylcholine. On basis these observations, it concluded that probably diminishes efficiency synaptic inhibition cells.