TIME-DEPENDENT CHANGES IN RAT HIPPOCAMPAL SYNAPSIN-I MESSENGER-RNA EXPRESSION DURING LONG-TERM POTENTIATION

We studied the time-dependent changes in synapsin I mRNA levels after hippocampal long-term potentiation (LTP) in rats in vivo. Following LT P induction by stimulating the perforant path, synapsin I mRNA express ion in the granule cell layer of the dentate gyrus ipsilateral to stim ulation increased significantly in a time-dependent manner. From 2 to 8 h after stimulation, the synapsin I mRNA levels in the ipsilateral d entate gyrus were significantly higher than those of controls subjecte d to a sham procedure. The synapsin I mRNA level (157.4 +/- 7.1% of th e control level, mean +/- SEM) was at a maximum 8 h after stimulation. The synapsin I mRNA level of animals that received only test pulses d id not increase significantly, compared with the control level. These results suggest that the increased level of synapsin I mRNA is related to persistent enhancement of synaptic activity within the neural netw orks in which dentate granule cells participate in LTP. (C) 1998 Elsev ier Science B.V.