Histological examination of neuronal damage. The photomicrographs of the cerebral corpus striatum in a normothermic control rat treated with 0.9% NaCl solution (11 ml/kg) (A), a heat stroke rat treated with 0.9% NaCl solution (11 ml/kg) (B), or a heat stroke rat treated with the combined agent (DXM+HES) (C) immediately after the initiation of heat stroke. The striatal photomicrograph in a heat stroke rat treated with DXM (4 mg/kg) is similar to (B), and in a heat stroke rat treated with HES (10%, 11 ml/kg) is similar to (C) (data not shown). Twenty-five minutes after 80-min heat exposure, the corpus striatum of the rat treated with 0.9% NaCl solution showed cell shrinkage, pyknosis of the nucleus, and disappearance of nucleolus. After acute treatment with the combined agent, neuronal damage was reduced, as shown in C. The rats were sacrificed at 25 min after the termination of heat exposure or the equivalent time for the normothermic controls. Scale bar, 50 μm.