SEIZURE-INDUCED DIFFERENTIAL EXPRESSION OF MESSENGER-RNAS FOR NEUROTROPHINS AND THEIR RECEPTORS IN GENETICALLY FAST AND SLOW KINDLING RATS

Levels of messenger RNAs for brain-derived neurotrophic factor, nerve growth factor and neurotrophin-3, and their high-affinity receptors, T rkB and TrkC, were analysed in the brains of genetically fast and slow kindling rats using in situ hybridization. Basal expression of neurot rophins and Trk messenger RNAs in the hippocampal formation, amygdala, frontoparietal and piriform cortices did not differ between the two s trains. Al 2 h after the third generalized grade 5 seizure, induced by kindling stimulations in the amygdala, increased expression of brain- derived neurotrophic factor messenger RNA was detected in the dentate gyrus granule cell layer, amygdala, frontoparietal and piriform cortic es of the fast kindlers. Similar seizure-evoked increases of brain-der ived neurotrophic factor messenger RNA levels were also observed in th e amygdala and piriform cortex of slow kindlers. However, in these ani mals, brain-derived neurotrophic factor messenger RNA expression was n ot significantly altered by the seizures in the dentate gyrus granule cell layer and frontoparietal cortex. Furthermore, the seizure-induced increase of nerve growth factor, TrkB and TrkC messenger RNAs and dec rease of neurotrophin-3 messenger RNA levels in the dentate gyrus gran ule cell layer was only observed in fast, but not in slow, kindlers. T he neurotrophins are believed to regulate synaptic plasticity and effi cacy and to facilitate long-term potentiation and kindling epileptogen esis. The present data suggest that the slow and fast kindling rates i n the two strains studied here might partly be due to differences in s eizure-evoked neurotrophin and Trk synthesis. Copyright (C) 1996 IBRO.