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 extracel lular release of acetylcholine (ACh) in the parietal lobe of the cereb ral cortex was examined in conscious rats using the microdialysis tech nique. Innocuous mechanical stimulation was delivered for 10 min to th e skin of a hindlimb by gentle brushing with a toothbrush. Extracellul ar release of ACh significantly increased in response to brushing of a hindlimb either contralateral or ipsilateral to the unilateral pariet al cortex where ACh release was measured. There was no significant dif ference in the stimulation of ACh release by brushing of either the co ntralateral or ipsilateral hindlimb. These results demonstrate that cu taneous innocuous mechanical stimulation can increase extracellular re lease of ACh in the cerebral cortex. Unilateral brushing produces an i ncrease in ACh release in the bilateral cortices. We suggest that one of the physiological roles of the increased release of ACh in the cere bral cortex following cutaneous brushing may be to increase cerebral c ortical blood flow.