Effects of lifelong moderate caloric restriction on levels of neuropeptideY, proopiomelanocortin, and galanin mRNA

We are interested in how neuropeptides that regulate both food intake and r eproductive function change with age and how life-prolonging moderate calor ic restriction may influence the expression of these neuropeptides. We meas ured neuropeptide Y (NPY) and proopiomelanocortin (POMC) mRNA in the arcuat e nucleus (AN) and galanin (GAL) mRNA in the AN, paraventricular nucleus (P VN) and medial septum-diagonal band of Broca in young, middle-aged and old female rats on a controlled feeding regimen. Female Sprague-Dawley rats (7 weeks old) were placed on caloric restriction (CR; n = 70) which was 60% of ad libitum (AL) intake measured in control rats (n = 70). Rats were rapidl y decapitated 2.5 weeks following ovariectomy, when they were 4, 12, or 18 months old. Brains were frozen and coronal sections (12 microns) were cut a t -20 degrees C using a cryostat. Relative levels of NPY, POMC and GAL mRNA were measured using in situ hybridization histochemistry, cDNA clones comp lementary to rat NPY, mouse POMC and rat GAL were used to synthesize S-35-U TP-labeled cRNA probes. Slides were dipped in photographic emulsion. Silver grains were quantified using computer-assisted image analysis. Caloric res triction increased NPY mRNA/cell, decreased POMC mRNA/cell in the AN, and d id not influence GAL mRNA/cell. Age and caloric restriction did not influen ce the number of cells with detectable NPY mRNA, POMC mRNA or GAL mRNA. Rep roductive status at the time of decapitation influenced both the level and the number of cells expressing GAL mRNA in the PVN. In summary, CR differen tially affects levels of NPY, POMC and GAL mRNA in the AN. Zn this animal m odel, there was no statistically significant effect of age nor any interact ion between age and diet on expression of any of these genes between 4 and 18 months of age.