RESPONSES OF SYMPATHETIC-NERVES INNERVATING BLOOD-VESSELS IN INTERSCAPULAR, BROWN ADIPOSE-TISSUE AND SKIN DURING COLD STIMULATION IN ANESTHETIZED C57BL/6J MICE

The effect of cold stimulation on the activity of sympathetic nerves running along blood vessels in interscapular, brown adipose tissues (IBAT) and skin overlying IBAT was examined in 15, urethane-anesthetized, artificially ventilated, C57BL/6J mice. Cold stimulation was applied caudal to the pelvic area using a plastic bag containing iced water. The stimulation of 14-16 min duration reduced core temperature measured at the esophagus or muscle near the esophagus by approximately 4-degrees-C from a control temperature of about 38-degrees-C. The stimulation decreased the activity of the nerve branches to IBAT, while it increased the activity of the nerve branches to skin. Blood flow in the IBAT increased significantly following the stimulation; however, this effect was abolished by the denervation. These findings suggest that the sympathetic innervation of the blood vessels in the IBAT plays a major role in thermoregulation against cold by decreasing the vascular tone and thus increasing the IBAT blood flow. An increase in the IBAT blood flow would facilitate the dissipation of heat from the IBAT to various organs as well as the supply of energy stuffs to the IBAT.