Naloxone and long term potentiation of hippocampal CA3 field potentials in vitro

The effects of naloxone on potentiation of CA3 pyramidal cell field potentials induced by tetanization of the mossy fiber pathway was studied in the in vitro guinea pig hippocampal slice preparation. Naloxone in nanomolar concentrations prevented the development of long term potentiation and it is concluded that an opioid peptide is probably involved in the generation of the potentiation.