Comparison of Osborne-Mendel and S5B/PL strains of rat: central effects of galanin, NPY, beta-casomorphin and CRH on intake of high-fat and low-fat diets.

The effects of central administration of galanin, neuropeptide Y (NPY), beta-casomorphin(1-7) and corticotropin releasing hormone (CRH) on intake of either a high-fat or low-fat diet have been compared in two strains of rat, the dietary fat-sensitive Osborne-Mendel (OM) rat and the dietary fat-resistant S5B/Pl rat. Injection of galanin (0.1, 0.3 nmoles) into the 3rd cerebral ventricle stimulated the intake of both a high-fat and a low-fat diet in OM rats in a dose dependent manner but the response was significantly smaller in rats fed the low-fat diet. In S5B/Pl rats, galanin had a small stimulatory effect on food intake but only at a high dose (2 nmole). Beta-casomorphin(1-7) (5 nmoles), an opioid-like peptide, increased the intake of the high-fat but not the low-fat diet in OM rats, whereas S5B/Pl rats fed either a high-fat or low-fat diet did not respond to beta-casomorphin(1-7). Both strains showed a similar stimulatory response to NPY (0.1, 0.5 nmoles) on the intake of the high-fat or low-fat diet, but the magnitude of the response was attenuated in S5B/Pl rats. In contrast, the anorectic effects of CRH (0.26 nmoles) on food deprived animals was similar in both strains for both diets. We speculate that the regulatory system controlling the intake of fat activated by galanin and beta-casomorphin(1-7) may be defective in S5B/Pl rats.