Hypothalamic CRF neurons facilitate brain reward function.

Aversive stimuli activate corticotropin-releasing factor (CRF)-expressing neurons in the paraventricular nucleus of hypothalamus (PVNCRF neurons) and other brain stress systems to facilitate avoidance behaviors. Appetitive stimuli also engage the brain stress systems, but their contributions to reward-related behaviors are less well understood. Here, we show that mice work vigorously to optically activate PVNCRF neurons in an operant chamber, indicating a reinforcing nature of these neurons. The reinforcing property of these neurons is not mediated by activation of the hypothalamic-pituitary-adrenal (HPA) axis. We found that PVNCRF neurons send direct projections to the ventral tegmental area (VTA), and selective activation of these projections induced robust self-stimulation behaviors, without activation of the HPA axis. Similar to the PVNCRF cell bodies, self-stimulation of PVNCRF-VTA projection was dramatically attenuated by systemic pretreatment of CRF receptor 1 or dopamine D1 receptor (D1R) antagonist and augmented by corticosterone synthesis inhibitor metyrapone, but not altered by dopamine D2 receptor (D2R) antagonist. Furthermore, we found that activation of PVNCRF-VTA projections increased c-Fos expression in the VTA dopamine neurons and rapidly triggered dopamine release in the nucleus accumbens (NAc), and microinfusion of D1R or D2R antagonist into the NAc decreased the self-stimulation of these projections. Together, our findings reveal an unappreciated role of PVNCRF neurons and their VTA projections in driving reward-related behaviors, independent of their core neuroendocrine functions. As activation of PVNCRF neurons is the final common path for many stress systems, our study suggests a novel mechanism underlying the positive reinforcing effect of stressful stimuli.

Dietary Supplementation with Compound Probiotics and Berberine Alters Piglet Production Performance and Fecal Microbiota.

This study was conducted to investigate the effects of dietary supplementation with compound probiotics and berberine (CPB) on growth performance, nutrient digestibility and fecal microflora in weaned piglets. A total of 200 piglets 35 days old were randomly allocated to 5 groups, 4 replications in each group, and 10 piglets in each replication. Group A was the basal diet; group B was supplemented with antibiotics and zinc oxide; groups C, D and E were supplemented with 0.06%, 0.12% and 0.18% CPB, respectively. The experimental period was 42 d. The results indicated that there were no significant differences in average daily feed intake (ADFI), average daily gain (ADG) and feed conversion rate (FCR) among five groups (p > 0.05). However, mortality, diarrhea and rejection rates in the control group were higher than that in other groups. CPB could increase protein digestibility and serum IgG content (p < 0.05), while it could decrease serum urea nitrogen content and alkaline phosphatase activity (p < 0.05). Analysis of fecal microbiota showed that the relative abundances of Bacteroides and Firmicutes were increased, while the relative abundances of opportunistic pathogens such as Spirochaetae and Protebactreria were dramatically decreased in piglets fed with CPB or antibiotics, compared with the control group. Furthermore, CPB intervention increased the relative abundances of Prevotella_9, Megasphaera and Prevotella_2, while decreased the relative abundance of Prevotellaceae_NK3B31_group. Correlation analysis revealed that there was good correlation between serum indexes and fecal microbiota. It was suggested that CPB might be a promising antibiotic alternative for improving piglet health and immunity, decreasing mortality by positively altering gut microbiota.