Lesion of central part of the dorsomedial nucleus alters vasopressin but not corticotropin releasing hormone mRNA levels in rat hypothalamic paraventricular nucleus

Functional significance of neural projections from the hypothalamic dorsomedial nucleus (DMN) to the paraventricular nucleus (PVN) was investigated using surgical lesion of the central part of the DMN. Under basal conditions, DMN lesion resulted in a decrease in magnocellular vasopressin (AVP) mRNA levels in the PVN, rise in pituitary proopiomelancortin (POMC) mRNA concentrations and elevated plasma corticosterone levels. Corticotropin-releasing hormone (CRH) mRNA levels remained unaffected. In sham operated animals, osmotic stress induced by hypertonic saline injection failed to modify AVP mRNA, but increased CRH and POMC mRNA levels and peripheral hormone release. The rise in CRH mRNA levels after osmotic stress was potentiated in DMN lesioned animals. Thus, the DMN participates in the control of hypothalamic peptide gene expression and pituitary adrenocorticotropic function.