F. Canini et al., Inhibition of different types of nitric oxide synthase: effect on thermoregulation in the rat exposed to high ambient temperature, NEUROSCI L, 316(1), 2001, pp. 45-49
Vascular and immunological mechanisms are both likely to be involved in hea
tstroke, this condition being preceded by a decrease in cerebral blood flow
and an increase in brain cytokine concentrations. As the two mechanisms in
volve a nitridergic step, we analysed their respective role in heat toleran
ce by exposing vigil rats to heat after treatment with nitric oxide synthas
es (NOS) antagonists: non-specific inhibitors N-omega-nitro-L-arginine (LNA
) and N-nitro-L-arginine-methyl-ester (L-NAME); 7-nitroinclazol (neuronal N
OS inhibitor) and aminoguanidine (AG) (inducible NOS inhibitor). Heat expos
ure was interrupted when clinical signs occurred or when colonic temperatur
e reached 43 degreesC. LNA and L-NAME dramatically reduced heat tolerance,
while AG did not modify it. These results suggest the involvement of consti
tutive NOS in heat tolerance. Inducible NOS does not seem to be involved in
the occurrence of heatstroke. (C) 2001 Elsevier Science Ireland Ltd. All r
ights reserved.