Nitric oxide as a peripheral and central mediator in temperature regulation

In animals including humans nitric oxide (NO) serves as a biological messenger both peripherally at neuroeffector junctions and in the central nervous system where it modulates neuronal activity. Evidence for the involvement of NO in homeostatic control is accumulating also for temperature regulation in homeotherms. In the periphery an auxiliary role in the vasomotor control of convective heat transfer to heat dissipating surfaces and modulation of thermoregulatory heat generation, especially in brown adipose tissue as the site of nonshivering thermogenesis, are discussed as NO actions. At the central level a thermolytic role of NO in thermoregulation as well as in fever is assumed, however, experimental data opposing this view suggest that topical specificity may be important. At the level of single neurons, the observed interrelationships between thermosensitivity and responsiveness to NO are still not consistent enough to reconcile these data with the effects of NO-donors and inhibitors of NO-synthase on temperature regulation.