Experimental Epilepsy Models and Morphologic Alterations of Experimental Epilepsy Models in Brain and Hippocampus

Abstract

Epilepsy is a neurological disease arising from abnormal and uncontrollable electrical firings of a group of neurons appearing in the central nervous system. Experimental epilepsy models have been developed to assess the pathophysiology of epileptic seizures and to search for new effective anti-epileptic drugs. This chapter is designed to describe characteristics of experimental epilepsy models and morphological and anatomical changes of brain, particularly hippocampus (Figure 1), in these models. Because of the hippocampal neuronal hyperexcitability during epileptic seizures, hippocampus has been one of the best choices in terms of target area that reveals most efficiently the effects of seizures in experimental epilepsy models. The purpose of the study determines which model should be chosen for epilepsies. This type of studies may have three purposes: 1. Developing new drugs, 2. Exploring the mechanisms, 3. Determining the relationships between basic events and the development of events for epilepsy. An ideal model of epilepsy should have the following characteristics: 1. Seizures should be as the spontaneous recurrent seizures, 2. Seizures should be similar to seizures in humans, 3. The EEG pattern should be similar to related type of epilepsy, and 4. The frequency of seizures should be sufficient to test acute and chronic effects of drugs. However, there is no single model that meets all these criteria. Some researchers classify seizures according to generation of the epilepsy model, not according to seizures in humans. Experimental models are divided into three groups according to this classification: 1. experimental seizures induced by chemical convulsants or by electrical stimulation, 2. reflex epilepsies, and 3. idiopathic epilepsies. Epileptic seizures are classified in three groups: 1. Partial seizures, which can be further subdivided into simple partial seizures and complex partial seizures. 2. Generalized seizures which can be further subdivided into tonic, clonic, tonic-clonic (grand mal), absence (petit-mal) seizures, and status epilepticus. 3. Unclassified seizures. In experimental epilepsy studies, animal models have been developed according to this classification (Table-1).