Reversible Inactivation and Excitation of Nucleus Raphe Magnus Can Modulate Tail Blood Flow of Male Wistar Rats in Response to Hypothermia

The nucleus raphe magnus (NRM) is involved in thermoregulatory processing. There is a correlation between changes in the firing rates of the cells in the NRM and the application of the peripheral thermal stimulus. we examined the effect of reversible inactivation and excitation of NRM on mechanisms involved in tail blood flow (TBF) regulation in hypothermia. Hypothermia was induced in Male Wistar rats and cannula was implanted above the NRM. To evaluate the effect of nucleus inactivation on TBF, the amount of TBF was measured by Laser Doppler in hypothermic rats, before and after lidocaine microinjection into NRM. TBF was also measured after glutamate microinjection to assess the effect of nucleus excitation in hypothermic rats. Results indicated that after dropping TBF by hypothermia, microinjection of lidocaine into NRM significantly decreased TBF from 54.43 -/+ 5.7 to 46.81 -/+ 3.4, whereas glutamate microinjection caused a significant increase from 44.194 -/+ 0.6 to 98 -/+ 10.0 These data suggest that NRM have thermoregulatory effect in response to hypothermia