Spatial alterations in endothelin receptor expression are temporally associated with the altered microcirculation after brain trauma.

Abstract

OBJECTIVES: To study the cellular distribution of endothelin receptors A and B (ETrA and ETrB) in the post-traumatic sensorimotor cortex and hippocampus. MATERIALS AND METHODS: We inflicted closed head trauma to male Sprague-Dawley rats and visualized ETrA and ETrB immunoreactivity with 3,3'-diaminobenzidine. RESULTS: ETrA immunolabeling was the most prominent in pyramidal neurons 24 and 48 hours post-trauma, while it reached its peak in the microvasculature at hour 4. ETrB immunolabeling was observed in endothelial cells, perivascular neurons, smooth muscle cells (SM) and pericytes, the expression being the most pronounced 24 hours post-trauma. DISCUSSION: The results suggest that the vasoconstrictor effect of endothelin-1 (ET-1) is mediated primarily by ETrA. The dual effects of ETrB are reflected in its vasoconstrictor role at the vascular bed and conversely, in the attenuation of ET-1 availability and synthesis. We conclude that both receptors play a role in the disturbed microvascular autoregulation and in the sustained reduction of blood flow following trauma to the brain.