Homeostatic competition: evidence of a serotonin-gated spinoparabrachial pathway for respiratory and thermoregulatory interaction.

Control of breathing and thermoregulation are vital physiological functions for the maintenance of arterial blood gas and pH homeostasis and body temperature homeostasis, respectively. It is widely believed that these homeostatic regulation functions act independently of one another via certain set point or feedfoward/feedback control mechanisms that are specific to each system. Here, the notion of "homeostatic competition" is introduced to depict the interaction of the respiratory and thermal controllers in negotiating a minimum-work ventilatory pattern that is optimal for survival in the face of conflicting homeostatic objectives during thermal stress. It is proposed that such competitive respiratory-thermoregulatory interaction may be mediated by the lateral parabrachial nucleus in dorsolateral pons, a critical site which receives cutaneous thermoafferent information via a serotonin-gated spinoparabrachial pathway and has been shown to modulate both chemoreflex and thermoreflex responses.