Acetylcholine is a neuromodulator which is released throughout the central nervous system and plays an essential role in consciousness and cognitive processes including attention and learning. Due to its 'activating' effect on the neuronal and behavioral level its interaction with anesthetics has long been of interest to anesthesiologists. It is widely held that a reduction of the release of acetylcholine by general anesthetics constitutes part of the anesthetic effect. This notion is backed by numerous human and animal studies, but is also in seeming contradiction to findings that acetylcholine activates specific classes of inhibitory neurons: if acetylcholine excites elements within the neuronal network responsible for the release of the inhibitory neurotransmitter γ-aminobutyric acid (GABA), its withdrawal should diminish, not enhance, the effect of anesthetics.Focusing on cortical circuits, we present an overview of recent advances in cellular neurophysiology, particularly the interactions between inhibitory neuron classes, which provide insights on the interaction between acetylcholine and GABA.
Keywords: Acetylcholine; GABA; Interneuron; Neocortex; Neuromodulator.