The aim of our study was to investigate amino acid and energy metabolism of pentylenetetrazol (PTZ)-kindled animals. Glutamate dehydrogenase, aspartate-aminotransferase (AST), alanine-aminotransferase, gamma-glutamyltransferase, alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and creatine kinase (CK) were determined in the frontal cortex, cerebellum, hippocampus and pons-medulla regions of Hannover-Wistar rats. The rats were randomly divided into four experimental groups: (a) control; (b) rats which received a single PTZ injection in a subconvulsive dose of 40 mg/kg i.p.; (c) rats which received a single PTZ injection in a convulsive dose of 50 mg/kg i.p.; and (d) PTZ-kindled rats. Kindling increased ALP activity throughout the brain, elevated AST as well as LDH activity in the frontal cortex and hippocampus and decreased CK activity in the frontal cortex and cerebellum. Acute seizures of the same intensity did not induce these alterations. The observed effects therefore are obviously linked to the kindling phenomenon and not to seizure activity. Changes appeared mainly in the frontal cortex and hippocampus, i.e. brain areas believed to be directly involved in kindling.