POLYETHYLENE GLYCOL-INDUCED HYPOVOLEMIA AFFECTS THE EXPRESSION OF MCHMESSENGER-RNA, BUT NOT DYNORPHIN OR SECRETOGRANIN-II MESSENGER-RNAS, IN THE RAT LATERAL HYPOTHALAMUS

Two prominent neuron populations of the rat lateral hypothalamus expre ss genes encoding respectively the prepromelanin-concentrating hormone (MCH) or dynorphin (DYN) and secretogranin II (SGII). Their roles rem ain hypothetical in mammals. In the present study, we examined the cha nges in MCH, DYN and SGII gene expression in dehydrated rats compared to controls. Dehydration was obtained by subcutaneous injection of pol yethylene glycol (PEG) resulting in a large reduction of the extracell ular fluid volume. Using competitive semi-quantitative RT-PCR and in s itu hybridization methods, PEG-injected animals showed a significant i ncrease of MCH mRNA level but no variation of DYN and SGII mRNA levels . These results confirm previous observations suggesting that intra- a nd extracellular dehydration challenges affect different regulation ci rcuits; they indicate that both neuron populations could be involved i n the maintenance of body fluid homeostasis, directly, or indirectly, as integrators of various information leading to goal-oriented behavio ur. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.