Journal of Applied Physiology, Vol 47, Issue 4 813-817, Copyright © 1979 by American Physiological Society
Hypothermia induced by chlorpromazine or L-tryptophan: effects on treadmill performance in the heat
R. Francesconi and M. Mager
To study the effects of preinduced hypothermia on the physiological and
thermoregulatory responses to exercise in the heat rats were intravenously
administered either 100 micrograms of chlorpromazine (CPZ) or 200 mg/kg of
L-tryptophan (L-Trp) under restraint in a cold (4 degrees C) environment.
When rectal temperatures (Tre) reached 32-33 degrees C the rats were
removed to a hot environment (35 degrees C) where they ran on a level
treadmill (9.14 m/min) to hyperthermic exhaustion (Tre, 42.5-43 degrees C).
Both CPZ and L-trp hypothermia was effective in increasing significantly (P
less than 0.001) the time to hyperthermic exhaustion. However, the maximal
Tre and skin temperatures (Tsk) attained were unaffected by either
treatment. When the rats exercised on the treadmill, increments (degrees
C/min) in Tre and Tsk were significantly (P less than 0.02, minimal)
greater for the initially hypothermic animals compared to normothermic
controls. Cooling rates were unaffected by either treatment. We concluded
from these studies that, although preinduced hypothermia is extremely
effective in prolonging the time to hyperthermic exhaustion, no additional
beneficial thermoregulatory responses accrued as a result of this
treatment.
