Abstract
Water is used both for evaporative cooling during external heat stress or exercise-induced heat load and for replenishment of the extracellular fluid (ECF) compartment under conditions of dehydration; thus, competing requirements for fluid or electrolyte balance and temperature regulation are well documented for homeothermic animals and humans. Hypothalamic control of salt and fluid balance is structurally well defined, whereas the neuronal cytoarchitecture for thermoregulation remains fragmentary. Employing classic and transsynaptic neuronal tracing techniques, diencephalic structures specifically involved in the perception and/or integration of thermoregulatory or osmoregulatory signals as well as the efferent pathways controlling respective effector systems could be determined. Stimulation of the osmoregulatory or thermoregulatory autonomic circuitries in the rat, using expression of c-fos as marker of neuronal activity, led to differential activation of specific neuronal populations in hypothalamic nuclei such as the SFO, OVLT, PVN, and SON for osmoregulation and MPA, VMPO, LHA, and LS for thermoregulation. The MnPO, activated by both thermal and osmotic stimuli, plays a major role as an integrative structure involved in both central control systems. The enzyme nNOS, generating NO as neuromodulatory agent involved in the centrally controlled homeostasis of body temperature and the ECF, was found to be upregulated in the respective hypothalamic structures during either heat exposure or osmotic stimuli. The latter induced coexpression of Fos protein with nNOS in the same neurons, whereas Fos-positive cells and nitrergic cells were found codistributed as a result of thermal stimulation, indicating NO-mediated neuronal activation in nearest-neighbor target neurons.
Original language | American English |
---|---|
Title of host publication | Thermotherapy for Neoplasia, Inflammation, and Pain |
Editors | Mitsuo Kosaka, Tsutomu Sugahara, Klaus L. Schmidt, Eckhart Simon |
Place of Publication | Tokyo |
Publisher | Springer Japan |
Pages | 43-62 |
Number of pages | 20 |
ISBN (Print) | 978-4-431-67035-3 |
DOIs | |
State | Published - 2001 |