Interaction between long-term potentiation and the action of a peptide transmitter.

The interaction between long-term potentiation (LTP) and the action of a peptide transmitter was examined with evoked field potential recording in the CA1 region of the hippocampus in anesthetized male rats. The peptide transmitter transiently reversed and opposed the effects of LTP, and LTP reversed the action of the peptide transmitter. Because the peptide transmitter is released and has action particularly during sexual behaviors, the results are interpreted to mean that any memory trace encoded by potentiating mechanisms in the rat hippocampus is probably not accessible in the 20-30-min period of time surrounding reproductive activity in male rats.