Dexmedetomidine Attenuates Isoflurane-induced Neurocognitive Impairment in Neonatal Rats

2009 ◽  
Vol 110 (5) ◽  
pp. 1077-1085 ◽  
Author(s):  
Robert D. Sanders ◽  
Jing Xu ◽  
Yi Shu ◽  
Adam Januszewski ◽  
Sunil Halder ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Hippocampal Slice ◽  
Gamma Amino Butyric Acid ◽  
Amino Butyric Acid ◽  
Hippocampal Slice Cultures ◽  
Acid Type ◽  
Alpha2 Adrenoceptor ◽  
Organotypic Hippocampal Slice Cultures

Background Neuroapoptosis is induced by the administration of anesthetic agents to the young. As alpha2 adrenoceptor signaling plays a trophic role during development and is neuroprotective in several settings of neuronal injury, the authors investigated whether dexmedetomidine could provide functional protection against isoflurane-induced injury. Methods Isoflurane-induced injury was provoked in organotypic hippocampal slice cultures in vitro or in vivo in postnatal day 7 rats by a 6-h exposure to 0.75% isoflurane with or without dexmedetomidine. In vivo, the alpha2 adrenoceptor antagonist atipamezole was used to identify if dexmedetomidine neuroprotection involved alpha2 adrenoceptor activation. The gamma-amino-butyric-acid type A antagonist, gabazine, was also added to the organotypic hippocampal slice cultures in the presence of isoflurane. Apoptosis was assessed using cleaved caspase-3 immunohistochemistry. Cognitive function was assessed in vivo on postnatal day 40 using fear conditioning. Results In vivo dexmedetomidine dose-dependently prevented isoflurane-induced injury in the hippocampus, thalamus, and cortex; this neuroprotection was attenuated by treatment with atipamezole. Although anesthetic treatment did not affect the acquisition of short-term memory, isoflurane did induce long-term memory impairment. This neurocognitive deficit was prevented by administration of dexmedetomidine, which also inhibited isoflurane-induced caspase-3 expression in organotypic hippocampal slice cultures in vitro; however, gabazine did not modify this neuroapoptosis. Conclusion Dexmedetomidine attenuates isoflurane-induced injury in the developing brain, providing neurocognitive protection. Isoflurane-induced injury in vitro appears to be independent of activation of the gamma-amino-butyric-acid type A receptor. If isoflurane-induced neuroapoptosis proves to be a clinical problem, administration of dexmedetomidine may be an important adjunct to prevent isoflurane-induced neurotoxicity.

scholarly journals Isoflurane Neurotoxicity Is Mediated by p75NTR-RhoA Activation and Actin Depolymerization

2011 ◽  
Vol 114 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Brian P. Lemkuil ◽  
Brian P. Head ◽  
Matthew L. Pearn ◽  
Hemal H. Patel ◽  
John C. Drummond ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Hippocampal Slice ◽  
Hippocampal Slices ◽  
Neurotrophin Receptor ◽  
P75 Neurotrophin Receptor ◽  
Actin Depolymerization ◽  
Rhoa Activation ◽  
Hippocampal Slice Cultures ◽  
Developing Neurons

Background The mechanisms by which isoflurane injured the developing brain are not clear. Recent work has demonstrated that it is mediated in part by activation of p75 neurotrophin receptor. This receptor activates RhoA, a small guanosine triphosphatase that can depolymerize actin. It is therefore conceivable that inhibition of RhoA or prevention of cytoskeletal depolymerization might attenuate isoflurane neurotoxicity. This study was conducted to test these hypotheses using primary cultured neurons and hippocampal slice cultures from neonatal mouse pups. Methods Primary neuron cultures (days in vitro, 4-7) and hippocampal slice cultures from postnatal day 4-7 mice were exposed to 1.4% isoflurane (4 h). Neurons were pretreated with TAT-Pep5, an intracellular inhibitor of p75 neurotrophin receptor, the cytoskeletal stabilizer jasplakinolide, or their corresponding vehicles. Hippocampal slice cultures were pretreated with TAT-Pep5 before isoflurane exposure. RhoA activation was evaluated by immunoblot. Cytoskeletal depolymerization and apoptosis were evaluated with immunofluorescence microscopy using drebrin and cleaved caspase-3 staining, respectively. Results RhoA activation was increased after 30 and 120 min of isoflurane exposure in neurons; TAT-Pep5 (10 μm) decreased isoflurane-mediated RhoA activation at both time intervals. Isoflurane decreased drebrin immunofluorescence and enhanced cleaved caspase-3 in neurons, effects that were attenuated by pretreatment with either jasplakinolide (1 μm) or TAT-Pep5. TAT-Pep5 attenuated the isoflurane-mediated decrease in phalloidin immunofluorescence. TAT-Pep5 significantly attenuated isoflurane-mediated loss of drebrin immunofluorescence in hippocampal slices. Conclusions Isoflurane results in RhoA activation, cytoskeletal depolymerization, and apoptosis. Inhibition of RhoA activation or prevention of downstream actin depolymerization significantly attenuated isoflurane-mediated neurotoxicity in developing neurons.

scholarly journals Development of P301S tau seeded organotypic hippocampal slice cultures to study potential therapeutics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
James M. McCarthy ◽  
Jasmeet Virdee ◽  
Jessica Brown ◽  
Daniel Ursu ◽  
Zeshan Ahmed ◽  
...  
Keyword(s):  
Hippocampal Slice ◽  
Ex Vivo ◽  
Direct Access ◽  
In Vivo Studies ◽  
Dependent Manner ◽  
Ex Vivo Model ◽  
Concentration Dependent Manner ◽  
Hippocampal Slice Cultures ◽  
Organotypic Hippocampal Slice Cultures

AbstractIntracellular tau inclusions are a pathological hallmark of Alzheimer's disease, progressive supranuclear palsy, corticobasal degeneration and other sporadic neurodegenerative tauopathies. Recent in vitro and in vivo studies have shown that tau aggregates may spread to neighbouring cells and functionally connected brain regions, where they can seed further tau aggregation. This process is referred to as tau propagation. Here we describe an ex vivo system using organotypic hippocampal slice cultures (OHCs) which recapitulates aspects of this phenomenon. OHCs are explants of hippocampal tissue which may be maintained in culture for months. They maintain their synaptic connections and multicellular 3D architecture whilst also permitting direct control of the environment and direct access for various analysis types. We inoculated OHCs prepared from P301S mouse pups with brain homogenate from terminally ill P301S mice and then examined the slices for viability and the production and localization of insoluble phosphorylated tau. We show that following seeding, phosphorylated insoluble tau accumulate in a time and concentration dependent manner within OHCs. Furthermore, we show the ability of the conformation dependent anti-tau antibody, MC1, to compromise tau accrual in OHCs, thus showcasing the potential of this therapeutic approach and the utility of OHCs as an ex vivo model system for assessing such therapeutics.

A micromass culture method for rat embryonic neural cells

1983 ◽  
Vol 61 (1) ◽  
pp. 247-262
Author(s):  
O.P. Flint
Keyword(s):  
De Novo ◽  
Culture Method ◽  
Neural Cells ◽  
Gamma Amino Butyric Acid ◽  
De Novo Synthesis ◽  
Rat Embryo ◽  
Amino Butyric Acid ◽  
Acid Incorporation

A method of culturing early (13-day) rat embryo neural cells is described. Undifferentiated neural epithelium is disaggregated and cultured in small discrete islands. Cells that destined to differentiate as neurons actively segregate from the other cells in the island and aggregate together into small clumps. Other cells flatten and attach to the substrate and resemble typical fibroblasts throughout the culture period. The clumps of preneuron cells spread out forming large irregular foci. Spreading is mediated by active cell movements. Cells in the foci differentiate as a pure population of neurons identifiable by specific inhibition of 3H-labelled gamma-amino butyric acid incorporation or by labelling with a monoclonal antibody to GQ-ganglioside. The ganglioside is not found on the cell surface at the start of culture after trypsinization, but emerges during the 5 days of culture. The antigen is similarly not present in the embryonic mesencephalon in vivo at 13 days post coitum, only emerging later in the differentiated midbrain. There is thus an apparent de novo synthesis, which is paralleled in vivo and in vitro.

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