Dibucaine Mitigates Spreading Depolarization in Human Neocortical Slices and Prevents Acute Dendritic Injury in the Ischemic Rodent Neocortex

Abstract

BackgroundSpreading depolarizations that occur in patients with malignant stroke, subarachnoid/intracranial hemorrhage, and traumatic brain injury are known to facilitate neuronal damage in metabolically compromised brain tissue. The dramatic failure of brain ion homeostasis caused by propagating spreading depolarizations results in neuronal and astroglial swelling. In essence, swelling is the initial response and a sign of the acute neuronal injury that follows if energy deprivation is maintained. Choosing spreading depolarizations as a target for therapeutic intervention, we have used human brain slices and in vivo real-time two-photon laser scanning microscopy in the mouse neocortex to study potentially useful therapeutics against spreading depolarization-induced injury.Methodology/Principal FindingsWe have shown that anoxic or terminal depolarization, a spreading depolarization wave ignited in the ischemic core where neurons cannot repolarize, can be evoked in human slices from pediatric brains during simulated ischemia induced by oxygen/glucose deprivation or by exposure to ouabain. Changes in light transmittance (LT) tracked terminal depolarization in time and space. Though spreading depolarizations are notoriously difficult to block, terminal depolarization onset was delayed by dibucaine, a local amide anesthetic and sodium channel blocker. Remarkably, the occurrence of ouabain-induced terminal depolarization was delayed at a concentration of 1 µM that preserves synaptic function. Moreover, in vivo two-photon imaging in the penumbra revealed that, though spreading depolarizations did still occur, spreading depolarization-induced dendritic injury was inhibited by dibucaine administered intravenously at 2.5 mg/kg in a mouse stroke model.Conclusions/SignificanceDibucaine mitigated the effects of spreading depolarization at a concentration that could be well-tolerated therapeutically. Hence, dibucaine is a promising candidate to protect the brain from ischemic injury with an approach that does not rely on the complete abolishment of spreading depolarizations.

Optogenetic Analysis of Neuronal Excitability during Global Ischemia Reveals Selective Deficits in Sensory Processing following Reperfusion in Mouse Cortex

“…In vitro data indicate that ischemic depolarization can alter the balance between excitation and inhibition (Berger et al, 2008). Our study supports the idea that agents that reduce ischemic depolarization are potential therapeutic targets for stroke (Douglas et al, 2011;Risher et al, 2011). Reducing ischemic depolarization will help to maintain excitability and may prevent prolonged loss of sensory processing, leading to better outcomes following reperfusion.…”

The Role of 7,8-Dihydroxyflavone in Preventing Dendrite Degeneration in Cortex After Moderate Traumatic Brain Injury

“…All of the pyramidal neurons matched the criteria in layer II/III within the 2-mm area from edge of cavity were imaged and beadings on those dendrites were counted. Dendritic beading were defined as a rounded appearance that extending beyond the diameter of the parent dendrite and separated by “interbead ” segment [40]. …”

Ischemic stroke: experimental models and reality

“…Thus, the situation comes closer to the situation of focal cerebral ischemia. Most importantly, brain slices can also be prepared from human brain tissue and exposed to OGD experiments [102]. To study the cell-specific responses to stress such as OGD, the use of primary neuronal and glial cells is an invaluable benefit to understand their specific roles in stroke pathophysiology.…”