Sex-Specific changes in stress circuitry of the nucleus tractus solitarius following food deprivation in two rat strains

Food deprivation is used in many experimental models and is becoming increasingly prevalent in human diets. The impact of food deprivation on specific brain regions, including the nucleus of the tractus solitarius (NTS), a region that is involved in hunger and satiety sensing, remains to be determined. The NTS is a heterogeneous nucleus that includes corticotropin releasing factor receptor 1 (CRF1) neurons. CRF1 is implicated in both stress and appetite regulation, but the effects of food deprivation on CRF1 NTS neurons are unclear. We used immunofluorescence to examine the effects of 24-hour food deprivation on NTS activity in male and female Sprague-Dawley (SD) rats and CRF1-cre rats using cFos, an immediate early gene and neuronal marker of activation. NTS activity was increased in food deprived male but not female SD rats. In food deprived CRF1-cre rats, males had an increased proportion of active CRF1 + neurons with no change in females. In CRF1-cre rats, increased global NTS activity was observed in food deprived and refed males. Activation of CRF1 + neurons was also increased after deprivation but was reduced by refeeding. In females, food deprivation decreased global NTS activity that was then increased by refeeding, while CRF1 activity was unchanged. Collectively, these data suggest the NTS is differentially activated after food deprivation in a sex-specific manner, whereby males are more sensitive than females. These results provide insight into the role of brainstem stress circuitry in changes associated with conditions including intermittent fasting and eating disorders like anorexia.