Compatibility of bidirectional synaptic plasticity on hippocampo-prefrontal cortex pathway in rats

The hippocampo-prefrontal cortex pathway reportedly expresses long-term potentiation (LTP) and depression (LTD) in anesthetized rats. We examined whether there were any effects governing the induction of LTD after prior induction of LTP, or vice versa. Induction in sequence of LTP and LTD resulted in significantly stable changes of about 140 and 70% of a common control for 1 h each. The reversed sequence, LTD and LTP, showed a mirror image of about 65 and 135% of control, which were not different from the respective changes in the first sequence (P>0.3 for each). The correlation coefficient between changes was significantly positive in the first sequence and weakly negative in the reverse. These results indicate that this pathway can express compatibility of bidirectional synaptic plasticity while historical changes remain covert.