INNOCUOUS MECHANICAL STIMULATION OF THE HINDLIMB SKIN INCREASES EXTRACELLULAR RELEASE OF ACETYLCHOLINE IN THE CEREBRAL-CORTEX IN CONSCIOUS RATS

The effect of innocuous mechanical stimulation of skin on the extracellular release of acetylcholine (ACh) in the parietal lobe of the cerebral cortex was examined in conscious rats using the microdialysis technique. Innocuous mechanical stimulation was delivered for 10 min to the skin of a hindlimb by gentle brushing with a toothbrush. Extracellular release of ACh significantly increased in response to brushing of a hindlimb either contralateral or ipsilateral to the unilateral parietal cortex where ACh release was measured. There was no significant difference in the stimulation of ACh release by brushing of either the contralateral or ipsilateral hindlimb. These results demonstrate that cutaneous innocuous mechanical stimulation can increase extracellular release of ACh in the cerebral cortex. Unilateral brushing produces an increase in ACh release in the bilateral cortices. We suggest that one of the physiological roles of the increased release of ACh in the cerebral cortex following cutaneous brushing may be to increase cerebral cortical blood flow.