Pentylenetetrazol: failure to improve memory in mice.

Pentylenetetrazol purportedly improves memory in mice. Irwin and Benuazizi (1) suggested that pretrial doses of pentylenetetrazol improve short-term retention, that posttrial doses improve longer-term retention, and that the doses that facilitate retention are much less than those that produce convulsions. We tried to confirm the salient parts of their findings. Our method was similar to theirs. Male CF1 mice, 9 to 10 weeks old, were placed individually in a small antechamber that led into a larger chamber. When they stepped on the grids of the large chamber, the mice received 0.2 ma of electric shock for 0.5 second. When replaced in the antechamber, these mice took longer to reenter the large chamber than did unshocked mice, a result noted previously (1). Sixteen groups of 14 mice each received oral doses of either pentylenetetrazol or distilled water either 30 minutes before (pretrial) or immediately after the shock (posttrial). Either 8 minutes or 24 hours after the shock, the mice received a second trial, with a cutoff latency of 180 seconds for reentry. Procedure and results are summarized in Table 1. Pentylenetetrazol had no statistically significant effects on reentry latencies. The two groups receiving posttrial doses of 10 mg/kg had slightly longer reentry latencies than did the two corresponding control groups only because 16 of the drugged mice, as opposed to 11 of the control mice, did not reenter the shock chamber. As for the pretrial results, none of the drugged groups had significantly longer reentry latencies than did their control groups. Like Irwin and Benuazizi, we did find relatively great varia-