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The effect of fever on central alpha-MSH concentrations in the rabbit
Abstract:
The recent demonstration of the ability of centrally administered alpha-MSH to reduce pyrogen-induced fever in rabbits suggested a role for the peptide in central temperature control. Using a sensitive radioimmunoassay we have established the presence of immunoreactive alpha-MSH (ir alpha-MSH) in discrete CNS sites of the rabbit and have demonstrated a distribution of this activity similar to that seen in other species. Pyrogen-induced fever did not alter concentrations of ir alpha-MSH in tissue extracted from the paraventricular region of the hypothalamus, median eminence, midbrain central grey, preoptic/anterior hypothalamic region, pineal or pituitary. A decrease in arcuate nucleus ir alpha-MSH content was seen in febrile animals, although this change was not statistically significant. Significantly higher levels of ir alpha-MSH were detected in septal extracts of febrile rabbits (0.81/+-0.10 pg/micrograms protein, n=9) than in extracts from afebrile controls (0.54/+-0.04, n=17). This finding suggests the septum to be the central site of action of alpha-MSH to inhibit fever and further implies a modulatory role of the peptide in the central control of thermoregulation.
Insights
Alpha-melanocyte-stimulating hormone (alpha-MSH) plays a role in temperature control. This study found increased alpha-MSH in the septum of febrile rabbits, suggesting its involvement in fever inhibition.
Area of Science:
- Neuroendocrinology
- Physiology
- Immunology
Background:
- Central administration of alpha-melanocyte-stimulating hormone (alpha-MSH) reduces fever in rabbits.
- This suggests a role for alpha-MSH in central thermoregulation.
Purpose of the Study:
- To investigate the presence and distribution of immunoreactive alpha-MSH (ir alpha-MSH) in the rabbit central nervous system (CNS).
- To determine if fever affects ir alpha-MSH concentrations in specific CNS sites.
- To identify potential sites of action for alpha-MSH in fever modulation.
Main Methods:
- Radioimmunoassay (RIA) was used to measure ir alpha-MSH levels.
- Tissue samples were collected from various CNS regions of rabbits experiencing pyrogen-induced fever and afebrile controls.
- Concentrations of ir alpha-MSH were compared between febrile and afebrile states.
Main Results:
- Immunoreactive alpha-MSH was detected in discrete CNS sites, with a distribution similar to other species.
- Fever did not significantly alter ir alpha-MSH levels in the hypothalamus, median eminence, midbrain central grey, preoptic/anterior hypothalamic region, pineal, or pituitary.
- A non-significant decrease in arcuate nucleus ir alpha-MSH was observed in febrile rabbits.
- Significantly higher levels of ir alpha-MSH were found in the septum of febrile rabbits compared to controls.
Conclusions:
- The septum is suggested as a central site of action for alpha-MSH in inhibiting fever.
- These findings imply a modulatory role for alpha-MSH in the central control of thermoregulation.