Role of monoaminergic neurotransmitter systems in MDP-induced adjuvant effect.

The changes in delayed hypersensitivity in guinea pigs stimulated by muramyl dipeptide (MDP) after administration of agonists or antagonists of neurotransmitter systems were studied. Muramyl dipeptide was given in Freund's incomplete adjuvant three weeks before administration of drugs and antigen. Pretreatment with methiotepine, haloperidol and clonidine increased, while lisuride, apomorphine and yohimbine decreased the reaction of delayed hypersensitivity. These results suggest that serotonergic, dopaminergic as well as presynaptic alpha-receptors might have an inhibitory effect on cell-mediated immunity.