Participation of opiate delta-receptors in immunomodulation.

The activation of the opiate delta-receptors by the highly specific agonist DSLET evokes an immunoinhibitory effect in CBA mice which disappears with preliminary blockade of S2 serotonin receptors by cyproheptadine. The blockade of delta-receptors by the antagonist ICI 174,864 leads to stimulation of the immune response, which is tested on the basis of the number of rosette-forming cells. Neither stimulation nor suppression of immunogenesis are manifested in animals with a transsected hypophyseal stalk; this suggests the central action of the opioids. The increase in the immune response obtained with the administration of ICI 174,864 is associated with the dopaminergic system, since it is prevented by haloperidol. It was demonstrated that the thymus participates in the immune-stimulating influence of ICI 174,864.