The effects of selective opioid delta-receptor antagonists on stress-induced antinociception and plasma corticosterone levels in mice.

Antinociception produced in mice by a 3 min swim was attenuated by ICI 174,864 and by low doses of naloxone indicating the involvement of both delta- and mu-receptors. The degree of antinociception was not related to plasma corticosterone (CS) levels measured 11 min after the swim. Naloxone affected CS levels in control mice and appeared to reduce the CS response to stress: ICI 154,129 and ICI 174,864 did not produce consistent effects on plasma CS levels.