Poly I:C-induced fever elevates threshold for shivering but reduces thermosensitivity in rabbits

Area of Science:

• Physiology
• Thermoregulation
• Neuroscience

Background:

• Fever is a complex physiological response.
• Understanding fever's impact on thermoregulation is crucial.

Purpose of the Study:

• To investigate changes in shivering threshold and thermosensitivity during polyriboinosinic-polyribocytidylic acid (poly I:C)-induced fever in rabbits.
• To assess the influence of ambient temperature on these responses.

Main Methods:

• Conscious rabbits were subjected to ambient temperatures of 20°C and 10°C.
• Shivering threshold and thermosensitivity were measured before and after saline injection or poly I:C-induced fever.
• Thermosensitivity was determined by regressing metabolic heat production against hypothalamic temperature during cooling.
• Shivering threshold was defined as the hypothalamic temperature at which thermosensitivity intersected resting metabolic heat production.

Main Results:

• Saline injection had minimal effects on shivering threshold and thermosensitivity.
• Poly I:C-induced fever significantly altered shivering threshold, generally mirroring the biphasic fever pattern.
• At 20°C ambient temperature, the shivering threshold was elevated during fever's rising phase and decreased during recovery.
• At 10°C ambient temperature, shivering thresholds remained higher than regulated hypothalamic temperature, except during recovery.
• Thermosensitivity decreased by 30-41% during fever.

Conclusions:

• Fever profoundly affects the body's shivering response and temperature regulation.
• The shivering threshold dynamically adjusts during the fever cycle, influenced by ambient temperature.
• Reduced thermosensitivity during fever may contribute to altered heat production and dissipation mechanisms.