Alpha₂-adrenergic receptor agonists prevent emotional hyperthermia.

Area of Science:

• Neuroscience
• Physiology
• Pharmacology

Background:

• Emotionally significant stimuli, like threats, increase body temperature (emotional hyperthermia).
• Brown adipose tissue (BAT) thermogenesis, mediated by the sympathetic nervous system, significantly contributes to this response.
• Alpha2-adrenergic agonists are known to inhibit fever and shivering.

Purpose of the Study:

• To investigate if systemic administration of clonidine, an alpha2-adrenoceptor agonist, attenuates emotional hyperthermia.
• To determine if clonidine affects BAT thermogenesis and sympathetic nerve discharge during an emotional stressor.

Main Methods:

• Conscious, unrestrained rats were exposed to an intruder rat to elicit emotional hyperthermia.
• BAT and body temperature were measured using pre-implanted thermistors.
• Rats were treated with vehicle or varying doses of clonidine; BAT sympathetic nerve discharge was also studied in anesthetized rats.

Main Results:

• Clonidine dose-dependently reduced intruder-elicited increases in BAT and body temperature.
• Clonidine abolished BAT sympathetic nerve discharges evoked by activation of the lateral habenula in anesthetized rats.
• Statistical analysis confirmed a significant dose-dependent effect of clonidine on BAT and body temperature.

Conclusions:

• Central alpha2-adrenergic receptor activation attenuates emotional hyperthermia.
• This attenuation occurs through the reduction of BAT thermogenesis.
• Clonidine's inhibitory effect on BAT thermogenesis is a key mechanism in mitigating emotional hyperthermia.