The effects of subconvulsant and convulsant doses of pentylenetetrazol (PTZ) on cerebral blood flow (rCBF), permeability-capillary surface area products (rPS), and brain vascular spaces (BVS) were examined in 15 brain regions at 1 h, 24 h and 1 week after injection in male Sprague-Dawley rats. Brain histology was examined 3 days after injection. A dose of PTZ (50 mg/kg, i.p.), sufficient to trigger a single convulsive seizure, produced small regional changes in rCBF at 1 h, but not at 24 h or 1 week after injection. No significant changes in rPS or BVS were found at any time, and only mild histologic changes were observed. In contrast, a dose of PTZ (25 mg/kg) which failed to cause either convulsions or significant electrocorticographic changes, markedly increased rCBF and rPS. Some of these regional effects were still observed 1 week later. Similarly, more severe and extensive cellular changes followed treatment with the subconvulsive dose. These findings indicate that PTZ treatment can have prolonged effects on cerebrovascular functions and neuronal integrity even in the absence of convulsive activity.