ISOLATION-INDUCED AND DEHYDRATION-INDUCED CHANGES IN NEUROPEPTIDE GENE-EXPRESSION IN THE SHEEP HYPOTHALAMUS

Changes in neuropeptide gene expression in the hypothalami of sheep su bjected to psychological stress (isolation, 1 h; n=3) or dehydration ( 48 h; n=3) were examined using in-situ hybridization histochemistry. C ompared with nonstressed euhydrated control animals (n=3), isolation i nduced significant accumulation of mRNA for corticotrophin-releasing h ormone, pro-enkephalin and pro-dynorphin (DYN) in the paraventricular nucleus (PVN), but no change in mRNA content within the supraoptic nuc leus (SON). By contrast, dehydration significantly increased DYN mRNA in the magnocellular neurones of the PVN and SON. However, neither iso lation nor dehydration altered the expression of mRNA for vasopressin (AVP) in either the PVN or the SON. These results indicate that in the ovine hypothalamus (1) stress represents a powerful stimulus to co-or dinated neuropeptide synthesis and (2) expression of DYN mRNA and AVP mRNA may be independently regulated during changes in plasma osmolalit y.