Acetylcholine-induced inhibition in the cat visual cortex is mediated by a GABAergic mechanism.
The influence of iontophoretically applied acetylcholine (ACh) on single-unit activity in the visual cortex was studied in anesthetized cats. The dominant effect consisted of a slow facilitation of neuronal responses to moving light bars. This cholinergic action was sometimes paralleled by a decrease of the cells' selectivity to the direction of stimulus movement. In about one-third of the neurons studied ACh-iontophoresis suppressed maintained and visually driven activity within a few hundred milliseconds from the onset of its application. This effect was antagonized by concurrent iontophoresis of the muscarinic ACh-receptor antagonist scopolamine and the GABAA-receptor antagonist bicuculline methiodide. In 7% of the units studied a fast excitation was elicited by ACh application showing a similar time course as the rapid suppressive effect. It is concluded that ACh-induced inhibition is mediated by an activation of GABAergic interneurons. The role of cholinergic depression and facilitation in cortical information processing is discussed.
Müller
C M
CM
Max-Planck-Institut für Hirnforschung, Frankfurt/M F.R.G.
Singer
W
W
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002415:Cats; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000187:drug effects; D009039:Motion Perception / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects; D010775:Photic Stimulation; D012601:Scopolamine / Q000494:pharmacology; D014793:Visual Cortex / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D005680:gamma-Aminobutyric Acid; D012601:Scopolamine; D000109:Acetylcholine; D001640:Bicuculline