Electroshock seizures and brain chemistry after acute exposure to moderate cold

Abstract

Adult male rats were exposed to 2.5 C for 60 hr, and responses to threshold and supramaximal electroshocks were studied. Body weights, adrenal and thymus weights, and concentrations of water, sodium, potassium, chloride, and glycogen (or glucose) in brain, liver, muscle, and plasma were determined. Cold exposure markedly lowered seizure threshold, but failed to affect the pattern of maximal seizures. It also caused a significant drop in body weight, as well as the adrenal hypertrophy and thymic involution usually observed under stress. Biochemical studies revealed brain (cortex, cerebellum, and brain stem studied separately) to be much more stable in water and electrolyte content than are liver, muscle, and plasma. Sodium retention in muscle and liver and potassium depletion in muscle occurred in the cold-exposed rats, probably as a result of increased secretion of mineralocorticoids, but these changes were not apparent in brain. Calculations of distribution of water and electrolytes in brain showed a significant increase in effective extracellular sodium in the cortex. Cold exposure caused hyperglycemia and a significant drop in glycogen content in all tissues analyzed.