Neurogenesis in the thermoregulatory system

In response to various internal and external stimuli, neuronal progenitor cells in the hypothalamic area proliferate and differentiate to functionally working neurons even in adult animals. This is the case in the thermoregulatory system, especially in the process of heat acclimation. The heat acclimation process presents two different patterns, namely short-term and long-term heat acclimation. In rats, long-term heat acclimation is attained by exposing subjects to constant heat for more than 4 weeks, while short-term heat acclimation is established within several days of heat exposure. Heat exposure for more than 6 days facilitates cell proliferation in the ependymal layer of the third ventricle. The newborn cells then migrate into the hypothalamic parenchyma. After 33 days of heat exposure, the newborn cells abruptly differentiate to mature neurons. A part of the newborn cells are incorporated in a neuronal circuit in the hypothalamus. However, only 6 days of heat exposure hardly promote neuronal differentiation. An administration of mitosis inhibitor interferes with cell proliferation in the hypothalamic area and attenuates heat acclimation-induced improvement of heat tolerance. Long-term, but not short-term, heat acclimation may be established by generating new functional neurons in the hypothalamic area, which is where an important part of the thermoregulatory circuitry exists in rats.