An update on thermosensitive neurons in the brain: from cellular biology to thermal and non-thermal homeostatic functions.

TS neurons in the brain, particularly in the POA, play a central role in thermoregulation, based on the good correlations between the activity of TS neurons and the thermoregulatory responses. Such relationships have been observed during (1) thermal (hypothalamic and peripheral) and (2) pharmacological (amines, neuropeptides, cytokines, and exogenous drugs) stimulations, (3) during modulation of neural inputs from extraPOA brain regions, and (4) during actual thermoregulatory responses. In vitro studies utilizing tissue slice preparations and dissociated cellular preparations have revealed some mechanisms of thermal transduction of central TS neurons, which are apparently endowed with the unique characteristics of thermosensitivity. The high degree of convergence of thermal signals from local and remote sites on TS neurons suggests that locally TS neurons in one site of CNS are connected to TS neurons in the other sites, thus forming neural networks of TS neurons within the brain and the spinal cord. The findings that 40-70% of POA TS neurons respond to divergent types of non-thermal homeostatic signals and have abundant mutual connections with divergent areas of brain (limbic system and association cortices) indicate that TS neurons may be involved in the coordination of thermal and non-thermal homeostatic functions controlled in the hypothalamus.