Long-term depression is reliably induced in rats at 30 days of age

Previously we showed that long-term depression (LTD, a lasting diminishment in synaptic strength) can be reliably induced in the hippocampal dentate gyrus of both adult and 2-week old freely moving rats. Results from these studies indicated both age- and frequency-dependent alterations in the frequency response profile of the perforant path/dentate gyrus synapse. In the present study, we designed experiments to assess whether these frequency-response changes are sustained over the extent of time spanning the perinatal period and early adulthood. Dentate evoked field potentials were recorded and analyzed using the population spike amplitude (PSA) measure following sustained stimulation (900 pulses) of the lateral perforant pathway at various frequencies. Preliminary results suggest that LTD can reliably be induced in the 30-day old freely moving rat, and that such LTD is frequency dependent. These preliminary results, although representative of only 5 animals, appear to be consistent with our previously published findings of frequency and age effects on LTD transition to long-term potentiation (LTP) in the freely moving rat model.