Regulation of gastrointestinal activity in response to continuous low temperature in the Daurian ground squirrel.

Low temperature is an important environmental factor influencing the phenotypic plasticity of the gastrointestinal (GI) tract. However, it remains unclear how GI activity is regulated to cope with low temperature stress. The Daurian ground squirrel (Spermophilus dauricus) is a typical hibernator, which exhibits tolerance to low temperature.This study investigated the expression of hypothalamic appetite-regulating factors and GI activity-regulating factors in ground squirrels exposed to low temperature. The results showed that after continuous low temperature exposure (5 ± 1 °C for 6 days), the immunoreactive expression of c-Fos and neuronal nitric oxide synthase (nNOS) was significantly increased in the arcuate nucleus (ARC), dorsomedial hypothalamic nucleus (DMH), lateral hypothalamic area (LHA), and paraventricular nucleus (PVN); the neuropeptide Y (NPY) expression was upregulated in the ARC, LHA, and PVN. The mRNA expression of gastric nNOS, NPY, CHRM2, HTR4, ADRB2 and GHRL was significantly downregulated under low temperature. Correspondingly, the protein expression of M2mAChR, 5-HT4R, and ADRB2 was decreased, whereas expression of nNOS and GHRL was increased. In the jejunum, the mRNA expression of the above genes, as well as the protein expression of nNOS, M2mAChR, 5-HT4R, ADRB2, and GHRL, was elevated. These results indicate that low temperature stress can significantly activate hypothalamic neural circuits involved in appetite and motility regulation, while suppressing gastric gene expression and activating intestinal gene expression, which likely modulates gastric emptying and enhances intestinal function, enabling the ground squirrel to meet basal energy requirements under short-term low temperature stress, reflecting the remarkable plasticity of the GI tract.