14 Aug 1998

Acetylcholine has different effects on the excitability of different neuronal types, according to work by Xiang, et al, published in today's Science. The researchers examined two subtypes of interneurons in layer V of rat visual cortex. Acetylcholine excited low-threshold spike (LTS) cells through nicotinic receptors, whereas it elicited hyperpolarization in fast spiking (FS) cells through muscarinic receptors. Axons of LTS cells were mainly distributed vertically to upper layers, and those of FS cells were primarily confined to layer V. Thus, cortical cholinergic activation may reduce some forms of intralaminar inhibition, promote intracolumnar inhibition, and change direction of information flow within cortical circuits. This finding could contribute insights into the understanding of how information processing is disrupted by loss of acetycholine in Alzheimer's disease.—June Kinoshita