Comparison of the effects of intra-third ventricular administration of interleukin-1 or platelet activating factor on ACTH secretion and the sympathetic-adrenomedullary system in conscious rats.
The effects of centrally administered interleukin-1 beta (IL-1) or platelet activating factor (PAF) on adrenocorticotropin (ACTH) and catecholamine secretion, blood pressure and heart rate were examined to determine if these agents stimulate similarly the hypothalamic-pituitary-adrenal (HPA) axis or the sympathetic-adrenomedullary system. Intra-third ventricular administration of IL-1 (50, 200 ng) evoked significant ACTH secretion. Centrally administered IL-1 (50 ng) elevated plasma noradrenaline and adrenaline levels, systolic blood pressure and heart rate. Plasma ACTH, noradrenaline and adrenaline levels were also increased by the higher dose (200 ng) of IL-1 while systolic blood pressure and heart rate were not affected. Intra-third ventricular administration of 9 micrograms of PAF elevated the plasma ACTH level while 3 micrograms of PAF did not stimulate ACTH secretion. Neither dose of centrally administered PAF affected any plasma catecholamine level or systolic blood pressure. These results suggest that central IL-1 stimulates both the HPA axis and the sympathetic-adrenomedullary system, that a higher dose of IL-1 stimulates a mechanism to antagonize the elevation of blood pressure and heart rate and that central PAF is not involved in the control of the sympathetic-adrenomedullary system. Thus, IL-1 and PAF do not interact in the brain, although they interact peripherally.
Hashimoto
K
K
Second Department of Internal Medicine, Kochi Medical School, Japan.
Hirasawa
R
R
Makino
S
S
D000313:Adrenal Medulla / Q000187:drug effects*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000378:metabolism*; D006339:Heart Rate / Q000187:drug effects; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D007276:Injections, Intraventricular; D007375:Interleukin-1 / Q000008:administration & dosage*; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects; D010972:Platelet Activating Factor / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000187:drug effects*
D002395:Catecholamines; D007375:Interleukin-1; D010972:Platelet Activating Factor; D000324:Adrenocorticotropic Hormone