Kainic acid lesion of the striatum leads to the disruption of the striatonigral regulatory loop. Although microdialysis showed an increase in dopamine release, two days after kainic acid injection, 3-methoxytyramine levels are dramatically decreased. This suggests that the postsynaptic membrane-bound catechol-O-methyltransferase (COMT), but not the glial COMT, is responsible for the formation of measured 3-methoxytyramine.