Journal of neuroscience methods
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J. Neurosci. Methods · Dec 2004
On-line monitoring of striatum glucose and lactate in the endothelin-1 rat model of transient focal cerebral ischemia using microdialysis and flow-injection analysis with biosensors.
In vivo studies on cerebral glucose and lactate metabolism following a brain insult require fast and sensitive monitoring techniques. Here we report on-line monitoring of ischemic events and metabolic changes following reperfusion in striatum of freely moving rats subjected to endothelin-1 (60-240 pmol) induced, transient focal cerebral ischemia using slow microdialysis (0.5 microl/min), fast sampling (every minute) and flow-injection analysis with biosensors for glucose and lactate. The high-time resolution provides detailed information on lactate rise times and duration of low glucose. ⋯ The lactate increase measured over a 2-h period after endothelin-1 infusion was highly correlated with striatal infarct size. In some rats oscillatory changes are observed which cannot be detected in traditional assays. The here-described monitoring technique applied in a clinically relevant rat model is a sensitive tool to study post-ischemic energy metabolism, effects of therapeutic interventions and its relationship with histological outcome.
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J. Neurosci. Methods · Dec 2004
Simultaneous monitoring of nitric oxide, oxyhemoglobin and deoxyhemoglobin from small areas of the rat brain by in vivo visible spectroscopy and a least-square approach.
Nitric oxide (NO) is a versatile molecule involved in a wide range of biological processes. Under physiological conditions, NO reacts with oxyhemoglobin (OxyHb) to form methemoglobin (MetHb) at a very high rate. Previous works have shown that MetHb is proportional to NO and that MetHb absorption contributes to the in vivo absorption spectrum recorded with visible spectroscopy using optical fibers. ⋯ A least-square approach with a fitting equation containing the in vitro spectrum of the main endogenenous chromophores was used. The validity of this approach was studied by increasing the endogenous MetHb level with NO infusion and by biliverdin perfusion. Data indicate that in vivo visible spectroscopy in combination with the least-square fitting method may be a useful tool for gaining insight into the roles of NO, hemoglobins and the interaction between them even from small cerebral areas.
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J. Neurosci. Methods · Dec 2004
Comparative StudyApplication of triple-probe microdialysis for fast pharmacokinetic/pharmacodynamic evaluation of dopamimetic activity of drug candidates in the rat brain.
The technique of microdialysis utilizing three simultaneously implanted probes in the anaesthetized rat enables monitoring of pharmacokinetic (PK) profiles of a tested drug both in blood (1st probe) and brain (2nd probe) compartments and the pharmacodynamic (PD) response of neurotransmitters (3rd probe) released into, or accumulating within the brain extracellular fluid (ECF). In the present study, the PK/PD characteristics of cocaine (psychostimulant, strong abuse potential) and methylphenidate (dopamimetic drug without reinforcing properties) and two novel NeuroSearch (NS) drug candidates, NS-A and NS-B, were examined in blood and brain microdialysates from the anaesthetized rats. The extracellular levels of dopamine (DA) were monitored in the striatum or prefrontal cortex. ⋯ Faster kinetics of NS-B and its delayed effect on extracellular DA suggests that this compound is metabolized to an active intermediate product, which itself exerts stronger dopamimetic activity in the rat prefrontal cortex that the original NS-B substance. The present study illustrates the feasibility of triple-probe microdialysis to monitor the rate of extracellular accumulation of a drug candidate and DA levels in vivo and compare the resulting PK/PD profiles to those obtained for cocaine and methylphenidate. These measures may serve as initial neurochemical indicators of potential psychomimetic or reinforcing properties of the tested substances.
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J. Neurosci. Methods · Dec 2004
Technical aspects of an impact acceleration traumatic brain injury rat model with potential suitability for both microdialysis and PtiO2 monitoring.
This report describes technical adaptations of a traumatic brain injury (TBI) model-largely inspired by Marmarou-in order to monitor microdialysis data and PtiO2 (brain tissue oxygen) before, during and after injury. We particularly focalize on our model requirements which allows us to re-create some drastic pathological characteristics experienced by severely head-injured patients: impact on a closed skull, no ventilation immediately after impact, presence of diffuse axonal injuries and secondary brain insults from systemic origin... ⋯ Our new model will henceforth allow a better understanding of neurochemical and biochemical alterations resulting from traumatic brain injury, using microdialysis and PtiO2 techniques already monitored in our Intensive Care Unit. Studies on efficiency and therapeutic window of neuroprotective pharmacological molecules are now conceivable to ameliorate severe head-injury treatment.