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June 1971

Acetylcholine and the Epileptiform Activity of Chronically Isolated Cortex: II. Microelectrode Studies

Arch Neurol. 1971;24(6):495-502. doi:10.1001/archneur.1971.00480360029003

Single neurons in the chronically isolated visual cortex of cats prepared as encéphale isolé fired rarely and usually in bursts corresponding to epileptiform electroencephalogram discharges. Microelectrophoretic application of acetylcholine induced or increased the firing of 20% of the neurons tested, ie, in the same proportion as in a previous study of intact visual cortex. In some neurons, acetylcholine facilitated burst discharges; in others, it abolished them by inducing repetitive firing; but in the majority of neurons firing bursts, acetylcholine was without effect. L-glutamate often had similar effects as acetylcholine. Although atropine blocked the facilitatory effect of exogenous acetylcholine, it did not antagonize the spontaneous neuronal firing whereas γ-aminobutyric acid promptly suppressed it. The results indicate that the paroxysmal neuronal discharges are not due to supersensitivity to endogenous acetylcholine.