Effect of electrical stimulation of "rewarding" areas of the hypothalamus on habituation and dishabituation to repeated mild cold exposures in C57BL/6J mice.
Four groups of 12-month-old C57BL/6J male mice had chronic electrodes implanted in the median forebrain bundle. In three groups the "rewarding" property of electrical stimulation was determined during a single 30-min session of self-stimulation (ISS) before the beginning of the experiment. In the fourth group this test was postponed until the end of experiment. Every two weeks for 12 weeks all animals were subjected to repeated 3-hr cold stress tests consisting of partial physical restraint at an ambient temperature of 10 degrees C. The time interval between tests No. 3 and No. 4 was intentionally delayed up to four weeks. During the 4-week interval, animals of one of the groups tested for ISS remained in their home cages; mice of the second ISS-tested group received daily 30-min sessions of brain stimulation; and animals of the third ISS-tested group were placed daily for 30 min in the experimental chamber where they had been tested for ISS previously but received no brain stimulation. Animals of the fourth group, which were not tested for ISS prior to the experiment, also were placed daily in the experimental chamber without brain stimulation. Repeated cold testing resulted in improvement of cold tolerance (decrease of the rate of decline of colonic temperature during cold exposure) in the second and third tests relative to the first cold test in all groups (cold habituation).(ABSTRACT TRUNCATED AT 250 WORDS)
Talan
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Laboratory of Behavioral Sciences, National Institute on Aging, Baltimore, MD 21224.
Engel
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D000818:Animals; D001831:Body Temperature; D001835:Body Weight; D003080:Cold Temperature; D004558:Electric Stimulation; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012201:Reward