Baroreceptors discharge due to bilateral aortic denervation evokes acute neuronal damage in rat brain

Deep hypothermic circulatory arrest in cardiothoracic surgery evokes severe brain damages. On the other hand, blood pressure stimuli discontinuation to the brain has been found to induce alterations in neurotransmitter release, including glutamate, in numerous brain regions. Furthermore, it is well established that excessive glutamate release can induce neuronal injury, a process called excitotoxicity. Aim of the present study was the evaluation of possible acute neuronal damage after bilateral aortic denervation (bAD), imitating the baroreceptors discharge during circulatory arrest. Male, Wistar rats underwent either bAD or Sham operation under continuous hemodynamic monitoring. Two hours after completion of the procedure, rats were sacrificed and the brains were dissected and cut in specific levels corresponding to selective brain regions, based on either their participation in neuronal circuits, regulating blood pressure, or their vulnerability, after deep hypothermic circulatory arrest. Slices were stained and examined under light microscope using morphometric techniques. Increased number of necrotic neurons were found among bAD rats in amygdaloid complex (p=0.005), motor cortex (p=0.001), CA1 and CA3 (p=0.02 and 0.015) but not in posterior hypothalamic nucleus and Purkinje cell. Higher ratios of necrotic neurons were found in amygdaloid complex (p=0.002), motor layer (p=0.003 and p=0.000) and the hippocampal CA1 region (p=0.027) of bAD rats. The present study shows that baroreceptors discharge due to bAD may induce acute neuronal loss in brain regions involved in blood pressure regulation. Neuronal loss might be attributed to excitotoxic phenomena and it is following the same topographic distribution seen in deep hypothermic circulatory arrest, revealing a concurrent to hypoxia/ischemia mechanism of brain damage.