Time-dependent aspects of CO2 induced amnesia and hippocampal monoamine metabolism in rats.

The time course of amnesia for a one-trial passive avoidance response after treatment with carbon dioxide (CO2) was studied. Amnesia developed gradually over the first 4 hr following the amnesic treatment. Once established, amnesia remained during a 4 week test period. Previously, we reported that acquisition of the passive avoidance response was attended with a rise in the hippocampal concentration of serotonin 24 hr later and that this rise was not observed when acquisition was followed by amnesic treatment. In the present study, it was found that a rise in hippocampal serotonin parallelled the transient retention of the avoidance response 2 hr after amnesic treatment. However, 2 weeks after acquisition and amnesic treatment no changes in hippocampal monomine metabolism could be detected. Hippocampal noradrenaline did not correlate with avoidance and amnesia.