Ontogeny of corticotropin releasing hormone gene expression in rat hypothalamus--comparison with somatostatin.

Using in situ hybridization histochemistry, corticotropin-releasing hormone gene expression is first detectable in the parvocellular portion of the rat paraventricular nucleus on the 17th fetal day. The prevalence of messenger RNA for corticotropin releasing hormone decreases perinatally, specifically between the 19th and 21st fetal days. By the 4th postnatal day, CRH gene expression is similar to that of the adult rat. Somatostatin messenger-RNA is detectable on the 14th fetal day in the periventricular nucleus. No perinatal hiatus in somatostatin gene expression is evident.