ATTENUATION OF HEMISPHERIC SWELLING ASSOCIATED WITH ACUTE SUBDURAL HEMATOMAS BY EXCITATORY AMINO-ACID ANTAGONIST IN RATS

Acute subdural hematoma (ASDH) gives rise to a mass effect not only by itself but also through unilateral hemispheric swelling, The present study tested the hypothesis that hemispheric swelling is mediated by m echanisms which involve excitatory amino acids (EAAs). After removal o f the subdural clot, introduced by homologous blood (0.1-0.2 ml), the % brain water was determined from the formula: ((wet weight - dry weig ht) / wet weight) x 100. The % brain water of the left hemisphere was significantly greater than that of the right hemisphere during the ini tial 6 hours after induction of ASDH in animals injected with 0.2 ml b lood. A less marked but significant increase was observed in the anima ls injected with 0.1 ml blood. Systemic pretreatment with kynurenic ac id (KYN; 800 mg/kg, i.p.), a broad-spectrum EAA antagonist, attenuated the increase in % brain water in the animals injected with 0.2 ml blo od. In order to determine the changes in cerebral metabolism induced b y the model of ASDH employed in the present study, we measured the cor tical cytochrome oxidase (CYO) activity, a marker of mitochondrial res piration, in a separate group of animals. The CYO activity estimated d ensitometrically from the histochemical staining was not significantly altered in the animals injected with either 0.1 or 0.2 ml blood, sugg esting absence of ischemia. These results indicated that the hemispher ic swelling associated with thin ASDHs may be partially mediated by me chanisms other than ischemia, in which EAAs appear to be involved.