Accommodation properties of isolated hippocampal neurons under conditions of an experimental model of epilepsy

A pilocarpine/lithium model of status epilepticus is an effective tool allowing one to study the principles of development of temporal epilepsy. It is believed that, in addition to the corresponding modifications of the efficacy of synaptic transmission, changes in the endogenous properties of neuronal activity can promote repetitive epileptiform activity. We measured the accommodation parameters of spike generation by isolated neurons of the CA1 hippocampal area obtained from 14-day-old rats 2 or 24 h after they had been subjected to an epileptization procedure, as well as from control rats of the same age. The spike activity of the neurons was initiated by their depolarization with a long-lasting stimulus in a current-clamp mode under conditions of perforated patch clamp. We found that the initial phase of accommodation manifested as a rapid increase in interspike intervals immediately after application of the depolarizing stimulus became significantly shorter in rats 24 h after epileptization; at the same time, the characteristics of the late phase of accommodation underwent no changes. In addition, the mean number of generated action potentials dropped. Such changes were not found in neurons of rats 2 h after epileptization. It is hypothesized that the above effect is compensatory and not injuring; it can develop because of prolonged abnormal activation of neurons in the course of epileptic attacks. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 211–218, May–June, 2006.