DEFICIENCY IN INDUCTION BUT NOT EXPRESSION OF LTP IN HIPPOCAMPAL SLICES FROM YOUNG-RATS

In this study we examine developmental changes between postnatal day ( PND) 4 and 14 in synaptic transmission and plasticity in the CA1 regio n of hippocampal slices. We confirm previous results that tetanus-indu ced long-term potentiation (LTP) in field recordings is diminished in slices from younger animals. LTP in whole-cell current-clamp recording s is also diminished in younger animals. However, robust LTP can be in duced in young animals if sufficient postsynaptic depolarization is pr ovided during LTP induction. Furthermore, we find differences in synap tic transmission between PND 4 and 14, suggesting that the depolarizat ion during tetanic stimulation in young tissue is ineffective to produ ce LTP. These results indicate that the smaller potentiation in field. recordings in slices from younger animals is attributable to insuffic ient postsynaptic depolarization during LTP induction rather than a de fect in expression mechanisms.