Effects of visual deprivation on the induction of epileptiform activity were studied in layer II/III of 29-39-day-old rat primary visual cortex. Field potentials were evoked by stimulation of layer IV in slices from control (CON) and dark-reared (DR) rats. Picrotoxin (PTX)-induced epileptiform activity was characterized by spontaneous and evoked epileptic field potentials (EFPs). The results showed that DR slices demonstrate greater susceptibility for induction of spontaneous EFP. PTX-induced changes in the characteristics of evoked field potentials also showed higher tendency of DR animals to generate epileptiform activity. In both groups, field potentials consisted of pEPSP1 (population excitatory postsynaptic potential 1, i.e., first negativity) and pEPSP2 (second negativity), respectively. There was no significant difference between the characteristics of field potentials in CON and DR slices. PTX significantly increased amplitude and duration of pEPSP2, but it had no significant effect on pEPSP1. Effects of PTX on pEPSP2 were significantly higher in DR slices. It is concluded that visual deprivation results in a heightened potential in layer II/III of the rat visual cortex to generate PTX-induced epileptiform activity. Copyright (C) 1999 Elsevier Science B.V.
- Brain slice
- Epileptic field potential