The involvement of opioid delta-receptors in stress induced antinociception in mice.

The selective opioid delta-receptor antagonist, ICI 154,129, attenuated the antinociception, assessed by prolongation of reaction time on the hot-plate, of mice which had swum for 3 min at 20 degrees C. This stress-induced antinociception was also sensitive to naloxone suggesting the involvement of both delta- and mu-receptors. A swim of 0.5 min at 30 degrees C did not produce antinociception on the hot plate but the writhing response to i.p. acetic acid was blocked by a non-opioid mechanism.