Parabrachial neuron types categorically encode thermoregulation variables during heat defense

Area of Science:

• Neuroscience
• Physiology
• Thermoregulation

Background:

• Heat defense is vital for survival and fitness.
• Thermosensory signal transmission to hypothalamic centers is key for regulating body temperature.
• The precise pathways for this signal transmission remain unclear.

Purpose of the Study:

• To investigate the neural circuits involved in transmitting thermosensory signals to the hypothalamus for heat defense.
• To identify specific neuron populations in the lateral parabrachial nucleus (LPB) that contribute to thermoregulation.
• To elucidate the functional roles of these identified neurons in physiological responses to heat.

Main Methods:

• Utilized genetic and functional analyses to identify and characterize neuron populations in the LPB.
• Investigated the circuitry connecting LPB neurons with downstream hypothalamic targets.
• Examined the roles of these circuits in regulating brown adipose tissue (BAT) thermogenesis and tail vasodilation.

Main Results:

• Identified glutamatergic prodynorphin and cholecystokinin neuron populations in the LPB that are recruited during elevated body temperature.
• Demonstrated that these nonoverlapping neuron types form distinct circuits with hypothalamic neurons.
• Showed that the prodynorphin circuit inhibits BAT thermogenesis and regulates energy expenditure, while the cholecystokinin circuit activates tail vasodilation.

Conclusions:

• Established that specific neuron types in the LPB are critical for heat defense.
• Uncovered distinct neural circuits for inhibiting BAT thermogenesis and activating vasodilation in response to warmth.
• Highlighted the early genetic and functional specificity of heat defense neurons in the LPB for encoding thermoregulatory variables.