Acute heat exposure causes cellular alteration in cerebral cortex of young rats

The possibility that prolonged heat exposure resulting in a failure of central thermoregulatory mechanism may induce cellular damage in brain was examined in young rats. Children exposed to Indian summer heat can develop sudden pathophysiological symptoms. Subjection of young animals to similar acute systemic heat exposure at 38 degrees C (relative humidity, 46%) for 4 h resulted in a profound hyperthermia, and behavioral stress symptoms e.g. salivation and prostration. Subsequent morphological examination of the brain tissue revealed profound cellular changes. In the cerebral cortex, dark neurons, swollen astrocytes, and expanded white and gray matter were quite frequent. At the ultrastructural level, collapse of microvessels, perivascular edema, vacuolation and damage to postsynaptic membrane was very common. Thus, profound hyperthermia can induce cellular changes by some direct or indirect (e.g. neurochemical) mechanism.