ACETYLCHOLINE-RELEASE IN RAT FRONTAL AND SOMATOSENSORY CORTEX IS ENHANCED DURING TACTILE DISCRIMINATION-LEARNING

We examined acetylcholine (ACh) release in the frontal cortex and in t he vibrissae representation in the somatosensory cortex in rats during the acquisition of a tactile discrimination or during nondiscriminati on control procedures. Microdialysis samples were collected for 1 h in the home cage and then for the duration of 30 discrimination or contr ol trials, across 5 consecutive days. Both groups showed significant t esting-induced increases in ACh release in both cortical sites. Howeve r, rats in the discrimination training group showed even greater testi ng-induced increases in ACh release in the somatosensory cortex and ha d a proportionately greater increase in somatosensory cortex than in f rontal cortex, relative to controls. The results suggest that, in addi tion to the widespread enhancement of ACh release associated with appe titive conditioning procedures in general, tactile discrimination trai ning causes a regionally specific enhancement in ACh release in the so matosensory cortex that is related to discrimination performance.