Effect of morphine on the excitability of rabbit hippocampus

The effects of morphine with respect to the excitability of hippocampal pyramidal cells were studied in acutely prepared rabbits. Microelectrode techniques were used for stimulation, recording, and iontophoresis of morphine and naloxone. Field potential responses were recorded before, during, and after drug delivery in different hippocampal layers. The data indicate that morphine administration results in a naloxone-reversible enhancement in pyramidal cell excitability. “Supersensitivity” was seen with repeated, but short-term, administration of morphine.