A test for analgesics as an indicator of locomotor activity in writhing mice.

Marked depression of locomotor activity was observed in writhing mice given acetic acid i.p. This depression of the activity was evidenced by a squatting posture in reaction to pain. The hypoactivity was reversed dose-dependently by nonnarcotic analgesics such as acetyl-salicylic acid, aminopyrine and mefenamic acid in smaller dosages than those obtained by the conventional writhing syndrome test, and was also reversed dose-dependently by narcotic analgesics such as morphine, pethidine and codeine. Consequently, this hypoactivity test proved to be useful for analgesics screening.