Regional differences in the expression of corticostriatal synaptic plasticity

Field recordings of responses to activation of corticostriatal afferents we re made in coronally sectioned rat brain slices. Each recording site was ca tegorized according to its medial to lateral and rostral to caudal position to investigate anatomical differences in synaptic plasticity. Individual r esponses were highly variable exhibiting extremes of tetanus induced depres sion and potentiation. Consequently, averaging masked the capacity of these synapses to express long-term forms of plasticity. Block of GABAA inhibiti on and elimination of dopaminergic input with 6-hydroxydopamine lesions bot h acted to increase the expression of potentiation, but again considerable variability was observed. Separation of recordings into medial and lateral groups revealed clear anatomical trends which contributed to the variabilit y observed in the total sample. Paired-pulse, post-tetanic and long-term po tentiation was greater in medial than in lateral groups in normal artificia l cerebral spinal fluid. Similar tendencies were seen after block of GABAA receptors with bicuculline. 6-Hydroxydopamine lesions in combination with b icuculline treatment reduced medial to lateral differences. Factoring in me dial to lateral trends revealed block of GABAA receptor mediated inhibition had its greatest effect on medial corticostriatal responses and 6-hydroxyd opamine lesions had their greatest effect on lateral responses. From these data we suggest anatomical variation in striatal circuitry may u nderlie regional differences in synaptic plasticity evoked by corticostriat al activation. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.