Cortical catecholamine changes and seizures induced by 4-aminopyridine in awake rats, studied with a dual microdialysis-electrical recording technique

We describe a rotatory electrical device that permits the simultaneous micr odialysis and electroencephalographic (EEG) recording, by means of bipolar electrodes attached to the microdialysis probe, in two brain regions of awa ke rats. Using this device, we have found that the microdialysis infusion o f 4-aminopyridine (4-AP) in the motor cerebral cortex produces intense beha vioral convulsions and EEG seizures in both the infused and the contralater al cortex. This convulsant action is accompanied by a remarkable increase o f extracellular dopamine (about 15-fold), norepinephrine (2.4-fold) and van illylmandelic acid (1.8-fold) concentration in the infused cortex. Delayed increases of these amines were observed also in the contralateral cortex. T he results suggest that 4-AP induces the release of catecholamines either t hrough a direct effect on nerve endings or as a consequence of seizures. (C ) 1999 Elsevier Science Ireland Ltd. All rights reserved.