Brown adipose tissue has sympathetic-sensory feedback circuits

Area of Science:

• Neuroscience
• Metabolic Physiology
• Thermogenesis Research

Background:

• Brown adipose tissue (BAT) is crucial for thermogenesis, primarily regulated by the sympathetic nervous system (SNS).
• Previous studies indicated separate brain pathways for SNS outflow to BAT and sensory system (SS) inflow from BAT, suggesting potential feedback loops.

Purpose of the Study:

• To investigate whether individual neurons participate in both sympathetic-sensory crosstalk concerning brown adipose tissue (BAT).
• To map the neuroanatomical connections involved in the feedback regulation of BAT thermogenesis.

Main Methods:

• Utilized dual viral tracer injections (PRV152 and H129) into interscapular BAT (IBAT) of Siberian hamsters.
• Employed Fast Blue (FB) retrograde tracer and c-Fos immunohistochemistry to identify activated neurons and their connections.
• Administered a β3-adrenoceptor agonist (CL316,243) to stimulate BAT and assess its effects on temperature and neural activity.

Main Results:

• Identified dually infected neurons (PRV152+H129) in brain regions critical for thermoregulation, including the raphe pallidus nucleus and nucleus of the solitary tract.
• Demonstrated that CL316,243 administration increased IBAT temperature, afferent nerve activity, and c-Fos expression in specific dorsal root ganglia (DRG) neurons.
• Confirmed the neuroanatomical existence of SNS-SS feedback loops originating from and projecting to IBAT.

Conclusions:

• Individual neurons can engage in sympathetic-sensory crosstalk, influencing BAT thermogenesis.
• The identified feedback loops suggest coordinated or redundant neural control mechanisms for regulating metabolic heat production.
• These findings provide crucial insights into the neural circuitry governing BAT function and energy homeostasis.