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Fever-specific changes in central MSH and CRF concentrations
Abstract:
The concentration of melanocyte-stimulating hormone (melanotropin; MSH) within the septal region of the brain increases during the fever, and septal injections of MSH are antipyretic. Corticotropin-releasing factor (CRF), when injected intracerebroventricularly, is also antipyretic. Using sensitive radioimmunoassays of microdissected tissue extracts, we established the presence of immunoreactive MSH (IRMSH) and CRF (IRCRF) within discrete central nervous system sites of the rabbit. Leukocytic pyrogen-induced fever and hyperthermia due to heat exposure did not alter concentrations of IRMSH or IRCRF in tissue extracted from preoptic-anterior hypothalamic or midbrain central gray regions. However, significantly greater levels of IRMSH were detected in septal extracts of febrile rabbits than in similar extracts from afebrile controls or heat-stressed animals. A significant decrease in IRCRF was detected in paraventricular nucleus extracts from febrile animals compared with extracts from afebrile controls or heat-stressed rabbits. Our results support the hypothesis that these central peptides have a role in temperature control during fever. Since no changes were detected in extracts from hyperthermic rabbits, it appears that changes in concentration of these neuropeptides within particular brain regions are specific to the febrile state and are not caused by elevation of body temperature or by nonspecific stress.
Insights
Melanocyte-stimulating hormone (MSH) levels increase in the rabbit brain
Area of Science:
- Neuroscience
- Endocrinology
- Physiology
Background:
- Melanocyte-stimulating hormone (MSH) and corticotropin-releasing factor (CRF) exhibit antipyretic properties.
- The roles of MSH and CRF in fever regulation within the central nervous system are not fully elucidated.
Purpose of the Study:
- To investigate the changes in MSH and CRF concentrations in specific brain regions during fever in rabbits.
- To determine if these changes are specific to fever or associated with general stress or hyperthermia.
Main Methods:
- Utilized sensitive radioimmunoassays to measure immunoreactive MSH (IRMSH) and CRF (IRCRF) in microdissected brain tissue from rabbits.
- Induced fever using leukocytic pyrogen and hyperthermia via heat exposure for comparison.
- Analyzed tissue extracts from preoptic-anterior hypothalamus, midbrain central gray, septum, and paraventricular nucleus.
Main Results:
- Fever significantly increased IRMSH levels in the septal region.
- Fever significantly decreased IRCRF levels in the paraventricular nucleus.
- Neither fever nor heat exposure altered IRMSH or IRCRF concentrations in the preoptic-anterior hypothalamus or midbrain central gray.
Conclusions:
- Central MSH and CRF concentrations in specific brain regions are altered during fever.
- These neuropeptide changes appear specific to the febrile state, not general hyperthermia or stress.
- Findings support a role for these central peptides in fever-induced temperature regulation.