Spinal alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors may mediate the analgesic effects of emulsified halogenated anaesthetics.

1. The present study was designed to investigate the relationship between spinal cord alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and the analgesic effects of emulsified halogenated anaesthetics. 2. After having established the mouse model of analgesia by intraperitoneal or subcutaneous injections of appropriate doses of emulsified enflurane, isoflurane or sevoflurane, we injected different doses of AMPA intrathecally and observed effects on the pain threshold using the hot-plate and acetic acid-induced writhing tests. 3. The results showed that intrathecal injection of AMPA (0.25, 0.5 and 1.0 ng) did not affect the pain threshold on the hot-plate test or the writhing times in conscious mice. In contrast, AMPA (0.25, 0.5 and 1.0 ng intrathecally) significantly and dose-dependently decreased the pain threshold on the hot-plate test and increased the writhing times in mice treated with emulsified anaesthetics. 4. These results suggest that spinal AMPA receptors may be important targets for the analgesic effects of emulsified enflurane, isoflurane and sevoflurane.