CHANGES IN EXTRACELLULAR LEVELS OF DOPAMINE METABOLITES IN SOMATOSENSORY CORTEX AFTER PERIPHERAL DENERVATION

This study examined the effects of a nerve transection on monoamine re lease from primary somatosensory cortex. The technique of microdialysi s was employed to sample extracellular levels of norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in the barrel field of freely mov ing rats following the surgical transection of the contralateral infra orbital nerve. Microdialysates obtained 3, 4, and 5 days after deaffer entation were analyzed using high-performance liquid chromatography wi th electrochemical detection. We found a significant increase in the r elease of the dopamine metabolites, DOPAC and HVA from the deafferente d cortex. Three days after deafferentation the release of DOPAC was th ree-fold higher in the deafferented than in the control animals, and r emained about 100% higher in the next two days in this group of animal s, The release of HVA showed a gradual increase following the deaffere ntation procedure, since a 92% larger value on day 3 increased to a 33 8% difference on day 5. On the other hand, the release rate of NE and the levels of the serotonin metabolite 5-HIAA were not significantly a ffected by the deafferentation procedure. These results are discussed in the context of the possible participation of dopamine in the reorga nization of the deafferented somatosensory cortex.