Accumbal TRH is downstream of the effects of isolation stress on hedonic food intake in rats

ABSTRACT

Emotional stress, through elevating corticosterone (CORT) levels may reduce feeding in rodents however when offered palatable food, stressed animals ingest more food compared to non-stressed controls. Nucleus accumbens (NAc) is part of the mesocorticolimbic system and participates in processing rewarding characteristics of food modulating palatable food intake, mainly when glucocorticoids are elevated. A possible mediator of CORT effects is accumbal thyrotropin-releasing hormone (TRH), which reduces chow intake in rats when administered into the NAc. We aimed to study the TRH role in hedonic feeding in stressed rats. For 14 days, animals with ad libitum access to chow or chow plus chocolate milk were either group-housed or singly-housed to induce stress. Rats with access to chocolate milk showed hyperphagia and decreased accumbal TRH mRNA levels, which were potentiated by stress. Results suggest that TRH downregulation was permissive of the increased palatable food intake. TRH injections into NAc of singly-housed animals with palatable food access reduced their food intake and increased serum CORT levels. The accumbal injections of a glucocorticoid receptor antagonist (mifepristone) in stressed rats with palatable food access, reduced only palatable food intake and increased accumbal TRH expression and serum CORT levels. This modulation of TRH mRNA when CORT signaling is modified suggests that accumbal TRH is downstream of glucocorticoids activity, which specifically increase palatable food intake. Our results strengthen the TRH involvement in regulating emotional aspects of hedonic feeding in stressed animals. Finding new therapies directed towards increasing TRHergic activity in NAc may be protective against overeating.

KEYWORDS:

• Palatable food
• stress
• thyrotropin-releasing hormone
• nucleus accumbens
• mifepristone

Acknowledgements

We want to thank Dr Paulina Soberanes Chávez for her help with the statistical analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the CONACYT (P de G., México) under Grant number 293918.

Notes on contributors

Elena Alvarez-Salas

Elena Alvarez-Salas: BSc. Nutrition, MSc. and PhD in Biochemical Sciences.

Aldo González

Aldo González: BSc. Nutrition.

Maria Isabel Amaya

Maria Isabel Amaya: Technician Biology.

Patricia de Gortari

Patricia de Gortari: BSc. Nutrition, MSc. in Biotechnology and PhD in Physiology.