Acute and chronic effects of endotoxin on cerebral circulation in lambs

Author:

Feng Susan Y. S.1,Samarasinghe Thilini1,Phillips David J.2,Alexiou Theodora1,Hollis Jacob H.3,Yu Victor Y. H.14,Walker Adrian M.1

Affiliation:

1. Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University;

2. Centre of Reproduction and Development, Monash Institute of Medical Research, Monash University; and

3. Department of Physiology, Monash University, Clayton, Victoria, Australia

4. Newborn Services, Monash Medical Centre;

Abstract

The impact of endotoxemia on cerebral endothelium and cerebral blood flow (CBF) regulation was studied in conscious newborn lambs. Bacterial endotoxin [LPS, 2 μg/kg iv] was infused on 3 consecutive days. Cerebrovascular function was assessed by monitoring CBF and cerebral vascular resistance (CVR) over 12 h each day and by the endothelium-dependent vasodilator bradykinin (BK) ( n = 10). Inflammatory responses were assessed by plasma tumor necrosis factor-α (TNF-α, n = 5). Acutely, LPS disrupted the cerebral circulation within 1 h, with peak cerebral vasoconstriction at 3 h (CBF −28 and CVR +118%, P < 0.05) followed by recovery to baseline by 12 h. TNF-α and body temperature peaked ∼1 h post-LPS. BK-induced vasodilatation (CVR −20%, P < 0.05) declined with each LPS infusion, was abolished after 3 days, and remained absent for at least the subsequent 5 days. Histological evidence of brain injury was found in four of five LPS-treated newborns. We conclude that endotoxin impairs cerebral perfusion in newborn lambs via two mechanisms: 1) acute vasoconstriction (over several hours); and 2) persistent endothelial dysfunction (over several days). Endotoxin-induced circulatory impairments may place the newborn brain at prolonged risk of CBF dysregulation and injury as a legacy of endotoxin exposure.

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology

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