Inflammatory Response in Patients under Coronary Artery Bypass Grafting Surgery and Clinical Implications: A Review of the Relevance of Dexmedetomidine Use

Figure 8

Neuroprotective mechanism(s) triggered by (α-)2-adrenoreceptors agonists. Presynaptically: (1) activation of outward rectifying K⁺ channels causing hyperpolarization; (2) inhibition of inward translocation of Ca²⁺ ions; (3) hyperpolarization resulting from action-1 causes reduced Ca²⁺ entry; (4) reduced intracellular Ca²⁺ (as a result of actions 2 and 3) causes diminished neurotransmitter release. Synaptically: (5) due to action-4 as well as reduced receptor sensitivity; (6) extrasynaptic scavenging of glutamate by astrocytes. Postsynaptically: (7) hyperpolarization reduces the activation of NMDA receptors by enhancing Mg²⁺ block and also causes reduced neuronal firing and reduced intracellular Ca²⁺ release; (8) due to actions 5 and 9. The reduced excitotoxic neuronal death due to combination of all actions but the main pathway is via a reduction in the free intracellular Ca²⁺ [106] (Modified of [157]).