The experimental study presented was undertaken to evaluate the role of thromboxane A2 contributing to aggravating cerebral ischemia, and to examine the effect of a thromboxane A2 synthetase inhibitor, trapidil on cerebral ischemia. Cerebral ischemia model was induced in 16 week old spontaneously hypertensive rats (SHR) by bilateral common carotid artery ligation (BLCL). Two doses of trapidil 15 mg/kg was intraperitoneally administered one dose 2 hr before and one dose 15 min after BLCL in SHR. While control animals only underwent BLCL. Brain tissue metabolites such as ATP, lactate and pyruvate, brain water content and plasma thromboxane B2 and 6 Keto PGF1 alpha were determined 3 hr after BLCL. Scanning electron microscopic observations were also recorded. ATP concentrations were 1.36 +/- 0.23 n moles/mg wet tissue in the trapidil treated group, 0.61 +/- 0.26 n moles/mg wet tissue in the control group, the difference between the treated and the control being significant (P less than 0.001). Lactate concentrations were 4.70 +/- 1.20 n moles/mg wet tissue in the treated group, 12.17 +/- 8.53 n moles/mg wet tissue in the control group, the difference between the treated and the control being significant (P less than 0.02). Pyruvate concentrations were 0.59 +/- 0.11 n moles/mg wet tissue in the treated group, 0.43 +/- 0.16 n moles/mg wet tissue in the control, the difference was also significant (P less than 0.05). Average water content was 78.87 +/- 0.59% in the treated group, 79.82 +/- 0.33% in the control.(ABSTRACT TRUNCATED AT 250 WORDS)