Serotonergic brainstem projections to hippocampus are thought to preferentially target and increase, via 5-HT3 receptors, the excitability of a distinct subpopulation of interneurons that primarily regulate GABAB-mediated inhibition in the dendritic region of pyramidal cells. Hippocampal slice work suggests that the between-burst hyperpolarization caused by slow (GABAB) IPSPs plays a significant role in controlling the strength of LTP induced with theta burst stimulation. According to the above observations it was assumed that blockade of hippocampal 5-HT3 receptors should reduce the hyperpolarization and thereby enhance both the frequency of the naturally occurring theta rhythm and the induction of LTP; moreover, if LTP-like mechanisms provide the substrate for certain forms of memory, such treatment was expected to facilitate learning. Each of the above predictions was tested and confirmed in the present set of experiments. The effects of ondansetron, a potent and selective antagonist of the 5- HT3 receptor, were examined on (1) frequency of the hippocampal theta rhythm, (2) induction of LTP in field CA1 of freely moving rats, and (3) retention of olfactory and spatial memory in tasks known to depend on an intact hippocampus. When injected intraperitoneally into freely moving rats, the drug reliably and significantly increased the frequency of the hippocampal theta rhythm in a dose-dependent manner. Second, at concentrations that facilitate theta frequency (100 micrograms/kg and 500 micrograms/kg), an injection of the drug 30 min prior to delivering electrical stimulation bursts significantly increased the magnitude and duration of LTP compared to that obtained in the same animals after vehicle injections.(ABSTRACT TRUNCATED AT 250 WORDS)
Background
Glibenclamide is a widely used sulfonylurea drug prescribed to treat type II diabetes mellitus. Previous studies have demonstrated that glibenclamide has neuroprotective effects in central nervous system injury. However, the exact mechanism by which glibenclamide acts on the blood–brain barrier (BBB) after intracerebral hemorrhage (ICH) remains unclear. The purpose of this study was to validate the neuroprotective effects of glibenclamide on ICH and to explore the mechanisms underlying these effects.
Methods
We investigated the effects of glibenclamide on experimental ICH using the autologous blood infusion model. Glibenclamide was administrated either immediately or 2 hr after ICH. Brain edema was quantified using the wet–dry method 3 days after injury. BBB integrity was evaluated by Evans Blue extravasation and degradation of the tight junction protein zona occludens‐1 (ZO‐1). mRNA levels of inflammatory cytokines were determined by quantitative polymerase chain reaction. Activation of the nucleotide‐binding oligomerization domain‐like receptor with a pyrin domain 3 (NLRP3) inflammasome and cell viability were also measured in cerebral microvascular endothelial b.End3 cells exposed to hemin. Neurological changes were evaluated by the Garcia score and rotarod test.
Results
After ICH, the brain water content, Evans Blue extravasation, and inflammatory cytokines decreased significantly in the ipsilateral hemisphere of the experimental compared to the vehicle group. Glibenclamide treatment and NLRP3 knockdown significantly reduced hemin‐induced activation of the NLRP3 inflammasome, release of extracellular lactate dehydrogenase, apoptosis, and loss of ZO‐1 in b.End3 cells. However, NLRP3 knockdown abolished the protective effect of glibenclamide.
Conclusion
Glibenclamide maintained BBB integrity in experimental ICH by inhibiting the activation of the NLRP3 inflammasome in microvessel endothelial cells. Our findings will contribute to elucidating the pharmacological mechanism of action of glibenclamide and to developing a novel therapy for clinical ICH.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.