Antinociceptive activity of sodium valproate in mice after chronic treatment.

1. Mice were given sodium valproate (0.71%) in the drinking fluid for 21 days. The antinociceptive activity, locomotor activity and body temperature changes were recorded at 7, 14 and 21 days. The possible carryover antinociceptive effects were also determined after valproate withdrawal for up to 3 days after 7-, 14- and 21-day treatment. 2. The antinociceptive activity was present only on days 7, 14 and 21 and, on withdrawal of the drug, the antinociceptive activity disappeared. 3. Thus, with this regimen of valproate administration, there was no persistent antinociceptive activity (carryover effect). There were essentially no effects of valproate on the locomotor activity and body temperature of mice. The antinociceptive effects were due to the presence of the drug and disappeared on valproate's withdrawal.