SYSTEMIC NEUTROPHILIA OBSERVED DURING ANAPHYLACTIC SHOCK IN RATS IS INHIBITED BY DOPAMINERGIC ANTAGONISTS

The involvement of the sympathetic and dopaminergic systems on blood neutrophilic leucocytosis observed during anaphylaxis was investigated. Blood neutrophil counts impressively increased 1 h after intravenous injection of ovalbumin (OVA, 250 mu g/kg) into OVA-immunized rats. The increase in neutrophil counts induced by OVA was abrogated after catecholamine depletion by reserpine. Either adrenalectomy or the alpha- and beta-adrenoceptor antagonists phentolamine and propranolol, respectively, had only minor inhibitory effects on neutrophilia induced by antigen. On the other hand, pretreatment with the dopaminergic antagonists chlorpromazine and pimozide significantly inhibited the neutrophilia. The intravenous injection of apomorphine, a dopaminergic agonist, increased neutrophil counts in naive animals, while chlorpromazine completely inhibited this phenomenon. These results suggest that dopaminergic mechanisms play a role in the systemic neutrophilia observed during anaphylactic shock.