Nitric oxide in the nucleus raphe magnus modulates cutaneous blood flow in rats during hypothermia

OBJECTIVES Nucleus Raphe Magnus (NRM) that is involved in the regulation of body temperature contains nitric oxide (NO) synthase. Considering the effect of NO on skin blood flow control, in this study, we assessed its thermoregulatory role within the raphe magnus. MATERIALS AND METHODS To this end, tail blood flow of male Wistar rats was measured by laser doppler following the induction of hypothermia. RESULTS Intra-NRM injection of SNP (exogenous NO donor, 0.1- 0.2 μl, 0.2 nM) increased the blood flow. Similarly, unilateral microinjection of glutamate (0.1- 0.2 μl, 2.3 nM) into the nucleus increased the blood flow. This effect of L-glutamate was reduced by prior intra NRM administration of NO synthase inhibitor N(G)-methyl-L-arginine or N(G)-nitro-L-arginine methyl ester (L-NAME, 0.1 µl, 100 nM). CONCLUSION It is concluded that NO modulates the thermoregulatory response of NRM to hypothermia and may interact with excitatory amino acids in central skin blood flow regulation.