LPS-INDUCED BLOOD NEUTROPHILIA IS INHIBITED BY ALPHA(1)-ADRENOCEPTOR ANTAGONISTS - A ROLE FOR CATECHOLAMINES

A role for catecholamines in the regulation of the blood neutrophilia induced by intravenous (i.v.) injection of lipopolysaccharide (LPS; 25 0 mu g/kg) was examined in Wistar rats by means of surgical adrenalect omy or pretreatment with adrenergic and dopaminergic antagonists into naive animals, Treatment of animals with a single dose (250 mu g/kg) o f LPS caused a dramatic increase in the number of circulating neutroph ils concomitant with a decrease in the number of these cells in the bo ne marrow, These effects were partially reversed when catecholamine st ores were depleted with reserpine, It was found that neither adrenalec tomy nor pretreatment with the dopaminergic antagonists, chlorpromazin e and pimozide, affected the changes in neutrophil counts induced by L PS, The injection of the alpha(1)/alpha(2)-adrenoceptor antagonist, ph entolamine, and the selective alpha(1)-adrenoceptor antagonist, prazos in, significantly decreased blood neutrophilia induced by LPS, However , neither the selective alpha(2)-adrenoceptor antagonist, yohimbine, n or the beta-adrenoceptor antagonist, propranolol, had any effect on LP S response. Taken together, these findings support the hypothesis that the catecholamine norepinephrine plays a role in the regulation of th e LPS-induced neutrophilia through activation of alpha(1)-adrenoceptor s.