Abstract
Orexigenic and anorexigenic peptides in the hypothalamus are involved in feeding behavior and also related to the stress responses. The noradrenergic pathway from the brainstem to the hypothalamus is also known to mediate stress responses. Prolactin-releasing peptide (PrRP) was isolated as an endogenous ligand of an orphan G-protein coupled receptor and colocalized with the noradrenergic neurons in the brainstem. Intracerebroventricular administration of PrRP activated CRH neurons in the parvocellular division of the PVN and caused increase of plasma corticosterone levels in rats. We found that restraint stress, nociceptive stimulus and acute inflammatory stress upregulated the PrRP gene expression in the brainstem in rats. In streptozotocin-induced diabetic rats and fa/fa Zucker diabetic rats, PrRP mRNA levels were significantly reduced in comparison with controls. In both diabetic rats PrRP mRNA levels were significantly increased after restraint stress. These data suggest that PrRP may be an important mediator of the stress response from the brainstem to the hypothalamus under normal and diabetic conditions. [J Physiol Sci. 2007;57 Suppl:S33]
