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Responses of hypothalamic and pituitary mRNA to physical and psychological stress in the rat
1Medical Unit, Charing Cross and Westminster Medical School, Westminster Hospital, London.
Abstract:
In-situ hybridization histochemistry was used to measure corticotrophin-releasing factor mRNA and proenkephalin A mRNA in the paraventricular nucleus (PVN), and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary of the rat. Levels of message were determined at 1, 2, 4 and 8 h after exposure to a variety of physical and psychological stresses. Corticotrophin-releasing factor mRNA in the PVN and POMC mRNA in the anterior pituitary increased in response to i.p. hypertonic saline, restraint and swim stress but not to cold stress. Proenkephalin A mRNA was raised only in response to the physical stress of i.p. injection of hypertonic saline. These results suggest that different afferent pathways and hypothalamic neurotransmitters may be involved in mediating the hypothalamic response to different physical and psychological stresses.
Insights
Different stresses activate distinct stress response pathways in rats. Corticotrophin-releasing factor (CRF) and pro-opiomelanocortin (POMC) mRNA levels rise with certain stresses, while proenkephalin A mRNA responds only to physical stimuli.
Area of Science:
- Neuroendocrinology
- Molecular Biology
- Stress Physiology
Background:
- The hypothalamic-pituitary-adrenal (HPA) axis is a key regulator of the stress response.
- Understanding how different types of stress activate specific molecular pathways is crucial for comprehending stress-related disorders.
Purpose of the Study:
- To investigate the differential expression of stress-related mRNAs in the rat brain and pituitary following various physical and psychological stressors.
- To elucidate the specific roles of corticotrophin-releasing factor (CRF), proenkephalin A, and pro-opiomelanocortin (POMC) in mediating stress responses.
Main Methods:
- In-situ hybridization histochemistry was employed to quantify mRNA levels.
- Measurements were taken in the paraventricular nucleus (PVN) and anterior pituitary of rats.
- mRNA levels were assessed at 1, 2, 4, and 8 hours post-stress exposure.
Main Results:
- Corticotrophin-releasing factor (CRF) mRNA in the PVN and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary increased following hypertonic saline injection, restraint, and swim stress.
- These specific mRNAs did not show significant changes in response to cold stress.
- Proenkephalin A mRNA levels were elevated solely after the physical stressor of hypertonic saline injection.
Conclusions:
- The study demonstrates that distinct physical and psychological stressors activate differential gene expression patterns in the neuroendocrine system.
- Different afferent pathways and hypothalamic neurotransmitters are likely involved in mediating the response to various types of stress.
- These findings contribute to understanding the nuanced molecular mechanisms underlying stress adaptation and response.