Activation of shivering and non-shivering thermogenesis by electrical stimulation of the lateral and medial preoptic areas.
Experiments were conducted to determine if the area of stimulation within the preoptic area and/or the magnitude of the electrical stimulus applied to the preoptic region would selectively alter the evoked thermogenic responses of normothermic and hypothermic rats. Urethane anesthetized male, Long-Evans rats kept at 37 degrees C, and later cooled to 34 degrees C, were given unilateral electrical stimulation (0.5 ms pulses of 200 microA at 50 Hz for 30 and 300 s) into either the medial preoptic area (MPO) or the lateral preoptic area (LPO). Temperature changes of intrascapular brown adipose tissue, TIBATs; of gastrocnemius muscle, Tms, tail, Tts and colonic Tcs via thermistor probes were recorded before and after stimulation along with differential, multi-unit EMG activity of the gastrocnemius muscle via implanted stainless steel electrodes. The group kept at 37 degrees C and given MPO electrical stimulations evoked graded increases in TIBATs above core dependent on the duration of the electrical stimulus but shivering did not occur and Tms did not rise. When kept at 34 degrees C the MPO-stimulated group showed greater increases in TIBATs than respective responses seen when the same stimuli were applied at 37 degrees C. The group maintained at 37 degrees C and given LPO stimuli over 300 s increased Tms as shivering occurred, yet no change in TIBATs were observed. When cooled to 34 degrees C LPO stimulation (30 or 300 s duration) showed greater shivering activity. Interesting, LPO stimulation of animals maintained at 34 degrees C also caused TIBAT to increase.(ABSTRACT TRUNCATED AT 250 WORDS)
Thornhill
J
J
Department of Physiology, University of Saskatchewan, Saskatoon, Canada.
Halvorson
I
I
D002001:Adipose Tissue, Brown / Q000502:physiology; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004576:Electromyography; D008297:Male; D011301:Preoptic Area / Q000033:anatomy & histology / Q000502:physiology*; D051381:Rats; D012768:Shivering / Q000502:physiology*