Does Central Nitric Oxide Play a Role in Thermoregulation

The diffusible stable free radical gas nitric oxide (NO) has been shown to function as a messenger molecule in the cardiovascular, immune, central and peripheral nervous systems (1,2). Concerning the nervous system, most of the principal criteria for considering NO to be a new neurotransmitter have been satisfied: the presence of a specific synthesizing enzyme, NO-synthase (NOS), specific Ca++-mediated activation of NOS in presynaptic neurones, and the presence of specific intracellular receptors: soluble guanylyl cyclase or ADP-ribosyltransferase in postsynaptic neurones (2,3). There is evidence that putative NO-synthesizing neurones are widespread over most parts of mammalian brain (4,5). However, the data related to the functional role of NO in the central nervous system are limited. Recent evidence favours a possible role for NO in central autonomic regulation (6). It was shown that endogenous formation of NO is required in the mechanisms associated with central respiratory rhythm generation (7). NO is also involved in the control of vasomotor tone within the ventrolateral medulla (8), and in cardiovascular regulation within the nucleus tractus solitarii (9,10).