GLUTAMATERGIC CONTROL OF THE EXPRESSION OF THE PROENKEPHALIN GENE IN RAT FRONTOPARIETAL CORTICAL SLICE CULTURES

The expression of the proenkephalin (PEnk) gene in rat neocortex devel ops during the first two postnatal weeks in an outside first-inside la st mode that is opposite to the gradient of neurogenesis. To test whet her the distribution of PEnk gene expression depends on the formation of the local circuitry, we examined the role of glutamate neurons in t he expression of the gene in slice cultures of rat frontoparietal cort ex. In situ and Northern blot hybridization were used for analysis. In slices explanted at postnatal day 6, the neuronal expression of the P Enk gene developed as in vivo. The expression responded to glutamate r eceptor agonists and antagonists in a time-dependent manner. After 2 d ays in vitro the expression of the gene was only enhanced by N-methyl- o-aspartate receptors, whereas after 7 days in vitro AMPA receptors al so regulated the expression. We concluded that glutamate neurons are i nvolved in the development and maintenance of the PEnk gene expression in the neocortex.