AJP - Endocrinology and Metabolism, Vol 259, Issue 4 E534-E541, Copyright © 1990 by American Physiological Society
Thermogenesis following meal feeding, isoproterenol, and cold in rats with LH lesions
S. W. Corbett, B. Roland and R. E. Keesey
Department of Psychology, University of Wisconsin, Madison 53706.
Responses to several thermogenic stimuli were measured in rats maintaining
stable but reduced body weights following lateral hypothalamic (LH)
lesions. Oxygen consumption was monitored in open-circuit respirometers
before and after exposure to cold (16.5 degrees C), intubation of a meal,
and isoproterenol injection (40 micrograms/kg 0.75). Observations were made
in both warm- (28 degrees C) and cold-acclimated (9 degrees C) LH-lesioned
rats. Cold exposure, intubation, and drug injection each caused marked
increases in heat production in sham- and LH-lesioned rats. This
thermogenic response was similar in magnitude and form for both groups.
Acclimation to 9 degrees C caused increased baseline levels of heat
production when measured at 28 degrees C. Subsequent exposure to
thermogenic stimuli revealed an exaggerated response to isoproterenol but
not intubation in cold-acclimated groups. The LH-lesioned cold-acclimated
rats responded in the same manner as sham-lesioned cold-acclimated rats.
These findings are in contrast to the immediate postlesion period when rats
show enhanced thermogenic activity. At reduced body weights LH-lesioned
rats show normal rates of heat production and make normal responses to
thermogenic stimuli. Enhanced thermogenesis does not appear to play a role
in the maintenance of chronically reduced body mass in LH-lesioned rats.
