Corticotropin-releasing hormone expression in supraoptic neurons after bilateral lesioning of the paraventricular nucleus in rats.

In situ hybridization histochemistry was used to demonstrate corticotropin releasing hormone (CRH) mRNA expression in the supraoptic nucleus of rats. Labeled cells with a range of grain densities were located mainly in the dorsal area of the nucleus. Long-term (6-weeks) lesioning of the hypothalamic paraventricular nucleus, which eliminates the major CRH pool from the hypothalamo-hypophyseal system resulted in an increased CRH mRNA density within supraoptic neurons compared to within sham-operated rats. Adrenalectomy failed to effect CRH mRNA content either in sham-operated or paraventricular-lesioned animals. CRH gene expression in supraoptic neurons of long-term paraventricular lesioned rats may exhibit a compensatory mechanism in the hypothalamus by which supraoptic neurons can take over some of the functions of the lesioned paraventricular CRH cells.