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 the vibrissae representation in the somatosensory cortex in rats during the acquisition of a tactile discrimination or during nondiscrimination control procedures. Microdialysis samples were collected for 1 h in the home cage and then for the duration of 30 discrimination or control trials, across 5 consecutive days. Both groups showed significant testing-induced increases in ACh release in both cortical sites. However, rats in the discrimination training group showed even greater testing-induced increases in ACh release in the somatosensory cortex and had a proportionately greater increase in somatosensory cortex than in frontal cortex, relative to controls. The results suggest that, in addition to the widespread enhancement of ACh release associated with appetitive conditioning procedures in general, tactile discrimination training causes a regionally specific enhancement in ACh release in the somatosensory cortex that is related to discrimination performance.