Focal Lesions in the Rat Central Nervous System Induced by Endothelin-1

Abstract

Axon injury following cerebral ischemia has received little scientific attention compared to the abundance of information dealing with the pathophysiology of grey matter ischemia. There are differences in the initial response of grey and white matter to ischemia in vitro. In this study we investigate whether the vasoactive peptide, endothelin-1, can generate a focal ischemic lesion in the white matter and compare the findings with endothelin-1-induced lesions in the grey matter. Using a minimally invasive technique to microinject endothelin-1 into selected brain regions, we observed an acute reduction in local MRI perfusion in the injected hemisphere after 1 hour. Twenty-four hours after microinjection of 10 pmoles of endothelin-1, we observed a loss of neurons in the grey matter. At 72 hours, neutrophils were absent and a macrophage/microglia response and astrocyte gliosis were detected. No breakdown in the blood-brain barrier was detected. After injection of 10 pmoles endothelin-1 into the cortical white matter, we observed prolific amyloid precursor protein-positive immunostaining (indicative of axonal disruption) and an increase in tau-1 immunostaining in oligodendrocytes at 6 hours. Similar to the grey matter lesions, no neutrophils were present, a macrophage/microglia response did not occur until 72 hours and there was no disruption in the blood-brain barrier. Focal injections of endothelin-1 into specific areas of the rat CNS represent a model to investigate therapeutic approaches to white matter ischemia.

Rodent models of focal stroke: Size, mechanism, and purpose

“…134 Intracerebral injection or surface application of endothelin-1 produces a local dose dependent ischemic lesion with minimal tissue edema. 135,136 Endothelin-1 application can be directed to distinct cortical regions to produce localized stroke within specific brain circuits. 137,138 Endothelin-1 can also be injected into subcortical white matter to produce focal subcortical stroke in the rodent.…”

A Versatile Murine Model of Subcortical White Matter Stroke for the Study of Axonal Degeneration and White Matter Neurobiology

“…A number of prior models of subcortical stroke have been described including focal injections of endothelin-1 into the internal capsule, subcortical white matter and striatum in the rat [12][13][14] and mouse 6,15 . More recent models of small focal strokes have utilized cholesterol microemboli injection in the carotid artery 16 and photothrombotic occlusion of a single penetrating arteriole 17 .…”

Models That Matter: White Matter Stroke Models

“…Approximately a 60% reduction in CBF leads to a hyperintense area detected by T2-weighted MRI within 24 h of injection [23]. The regional blood flow is restored by 3 h. Interestingly, ischemia induced by ET-1 administration does not appear to affect BBB integrity.…”

“…Endothelin is a naturally produced vascular endothelial cell peptide that may have paradoxical vasoconstrictive or vasodilatory activity when binding the respective endothelin receptors, ETA-R and ETB-R [21]. ET-1 is used to significantly reduce local blood flow to levels that produce ischemic injury when injected directly into parenchyma [22], and to induce precise and reproducible focal ischemic lesions in gray or white matter without disruption of the BBB [23]. This method has been largely used in modeling disease in rats.…”

“…When injected into rat subcortical white matter and striatum, ET-1 causes a short-lived (3 h) decline in regional CBF as measured by MRI and signal attenuation of an intravenous contrast agent [23]. Approximately a 60% reduction in CBF leads to a hyperintense area detected by T2-weighted MRI within 24 h of injection [23].…”