Increased hypothalamic neuropeptide Y expression in deprived preweanling rats is reversed by intragastric infusion of milk

Abstract

Lean, preweanling Zucker rat pups increase neuropeptide Y (NPY) expression in the hypothalamic arcuate nucleus in response to a 24-h deprivation of food, water, and maternal interaction as early as postnatal day 2 (P2) [10]. In this study, we examined if replacing nutritive or tactile aspects of maternal behavior to deprived rat pups could block the increased expression of hypothalamic NPY measured by in situ hybridization. On P2, P12, or P15, littermates were assigned to one of four treatment groups: (1) left with the dam for 24 h, (2) deprived of the dam for 24 h and given tactile stimulation in the form of periodic anogenital stroking to elicit urination and defecation, (3) deprived of the dam and given periodic anogenital stroking plus continuous gastric infusion of milk for 24 h, or (4) deprived of the dam and given periodic anogenital stroking plus continuous infusion of water for 24 h. We found that gastric infusions of milk normalized NPY expression at all three ages, gastric infusions of water did not on P2 and P15, and anogenital stroking alone had no effect. We suggest that the lack of milk is the major cause of increased hypothalamic NPY expression during maternal deprivation in lean Zucker pups.