Epileptiform activity induced by 4-aminopyridine in entorhinal cortex hippocampal slices of rats with a genetically determined absence epilepsy (GAERS)

• Published in: Brain research Vol. 841; no. 1; pp. 62 - 69
• Main Authors: Armand, V, Hoffmann, P, Vergnes, M, Heinemann, U
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 11.09.1999; Amsterdam Elsevier; New York, NY
• Subjects: 4-Aminopyridine; 4-Aminopyridine - pharmacology; Animals; Biological and medical sciences; CA1 area; Entorhinal Cortex - drug effects; Entorhinal Cortex - physiology; Entorhinal Cortex - physiopathology; Epilepsy, Absence - chemically induced; Epilepsy, Absence - genetics; Epilepsy, Absence - physiopathology; Epileptiform activity; Evoked Potentials - drug effects; Field potential; Genetic absence epilepsy rats of Strasbourg (GAERS); Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Hippocampus; Hippocampus - drug effects; Hippocampus - physiology; Hippocampus - physiopathology; In Vitro Techniques; Medical sciences; Nervous system (semeiology, syndromes); Neurology; Neurons - drug effects; Neurons - physiology; Paired pulse; Rats; Rats, Mutant Strains; Reference Values; Seizures - chemically induced; Seizures - physiopathology; CA1 area; Field potential; Paired pulse; Epileptiform activity; Hippocampus; Genetic absence epilepsy rats of Strasbourg (GAERS); Nervous system diseases; Rat; Epilepsy; Rodentia; Central nervous system; Electrophysiology; Petit mal; Cerebral disorder; Vertebrata; Mammalia; Entorhinal cortex; Animal; Central nervous system disease; Brain (vertebrata)
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(99)01781-3

Patients with absence epilepsy frequently develop convulsions later in life. We were therefore interested whether tissue from rats with a genetic absence epilepsy is more prone to seizure generation than normal animals. We compared the epileptiform activities induced by 4-aminopyridine (4-AP) induced in hippocampal–entorhinal cortex slices from genetic absence epilepsy rats of Strasbourg (GAERS, age 6 months) in which absence seizures have been present for about 4 months and from control non epileptic rats (NE). 4-AP induced short recurrent discharges in area CA1 of rat hippocampus, seizure-like events and interictal discharges in the entorhinal cortex. The various epileptiform discharges did not differ between the two strains in amplitude, duration and frequency. However, the latency for induction of different epileptiform activities by 50 μM 4-AP was significantly shorter in GAERS (about 16 min) than in NE rats (about 25 min). We also analysed differences in evoked field potentials (fp) in hippocampal area CA1 before, during and after application of 4-AP. Before application of 4-AP, responses to stimulation of Schaffer collateral were smaller in GAERS than in NE rats. Paired pulse potentiation was significantly larger in GAERS than in NE rats. 4-AP in the bath augmented the size of the evoked field potentials and this increase was larger in GAERS than in NE rats. Our findings show a greater excitability of hippocampal area CA1 in GAERS rats and a greater ability to develop 4-AP-induced epileptiform activity in combined hippocampal–enthorhinal cortex slices in GAERS than in NE rats.