ONTOGENY OF PRODYNORPHIN GENE-EXPRESSION IN THE RAT HYPOTHALAMUS

Opioid peptides, deriving from prodynorphin, proenkephalin and proopio melanocortin genes, have been shown to modulate brain development. Pro dynorphin gene expression was studied here by in situ hybridization in the developing rat hypothalamus using oligodeoxynucleotide probes. Pr odynorphin mRNA-synthetizing cells were observed in the ventromedial h ypothalamic nucleus, the supraoptic and the paraventricular nuclei fro m embryonic days 16, 18 and 21, respectively. We detected no transient expression of prodynorphin gene in the rat hypothalamus. Prodynorphin mRNA-containing cells were also observed prenatally in the striatum, the cortex, the hippocampus and the amygdala. When compared with data from the literature, our results suggest that translation may immediat ely follow transcription of prodynorphin gene in the supraoptic nucleu s. The presence of prodynorphin mRNA in the developing rat hypothalamu s also raises the possibility of an involvement of prodynorphin-derive d peptides in developmental processes and/or in the maturation of adul t neural regulations.