Suppressed neuropeptide Y (NPY) mRNA in rat amygdala following restraint stress

We have previously demonstrated that NPY produces anxiolytic-like effects through actions in the amygdala, and that anxiogenic-like effects of restraint stress are mediated through this structure. Here, we examined the effects of restraint stress on NPY mRNA levels in amygdala and several other brain regions. A sensitive solution hybridization-RNase protection assay (RPA) was developed, employing a combination of internal and external standards, which allowed absolute quantitation of NPY mRNA in tissue-samples of less than 10 mg. NPY mRNA levels were determined, following a 1-h restraint stress, in homogenates of tissue from the amygdala, neocortex, striatum and hypothalamus, and the time course of these effects was examined. A highly significant decrease in NPY-mRNA levels was seen in the amygdala at 1 h and 2 h following restraint, with levels returning to normal within 10 h. A similar effect was seen in the neocortex, but was less pronounced and slower in onset. Striatal and hypothalamic NPY expression was not significantly affected. Tissue levels of NPY-peptide were modestly decreased in the amygdala at 1 h following restraint and had returned to normal within 4 h. The present findings support the hypothesis that anxiety related behavioral effects of stress may in part be mediated through modulation of NPY function in the amygdala.