Adrenergic modulation of the blood neutrophilia induced by platelet activating factor in rats.
The involvement of catecholamines in blood neutrophilia observed after administration of platelet activating factor (PAF) to rats was studied. Intravenous (i.v.) injection of PAF (4 micrograms/kg) into naive rats more than doubled the number of neutrophils after 1 h. In contrast, PAF failed to induce neutrophilia in both adrenalectomized rats and those which had their catecholamine stores depleted by reserpine. PAF-induced neutrophilia was not inhibited by the selective antagonism of alpha 1- and alpha 2-adrenoceptors with prazosin and yohimbine, respectively. However, pretreatment with the beta-adrenoceptor antagonist, propranolol, significantly inhibited the phenomenon. Increase in the blood neutrophil counts was also achieved following the i.v. injection of the beta-agonist, salbutamol (1 mg/kg, i.v.). This response was clearly sensitive to propranolol but was not modified in rats submitted to adrenalectomy or reserpine pretreatment. The results suggest that the blood neutrophilia induced by the i.v. administration of PAF in rats is dependent on the stimulation of beta-adrenoceptors by catecholamines released from adrenal glands.
Altenburg
S P
SP
Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil.
Bozza
P T
PT
Martins
M A
MA
Tibiriçá
E V
EV
Silva
P M
PM
Cordeiro
R S
RS
Castro-Faria-Neto
H C
HC
D000315:Adrenalectomy; D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001853:Bone Marrow / Q000187:drug effects; D001854:Bone Marrow Cells; D007958:Leukocyte Count / Q000187:drug effects; D008297:Male; D009504:Neutrophils / Q000187:drug effects*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects*
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D010972:Platelet Activating Factor; D012110:Reserpine