title: Increase in the extracellular glutamate level during seizures and electrical stimulation determined using a high temporal resolution technique.
abstract: BACKGROUND
  Glutamate has been measured using different methods to determine its role under normal and pathological conditions. Although microdialysis coupled with HPLC is the preferred method to study glutamate, this technique exhibits poor temporal resolution and is time consuming. The concentration of glutamate in dialysis samples can be measured via glutamate oxidase using the Amplex Red method.
  
  
  METHODS
  A new device has been designed and constructed to rapidly deposit dialysis samples onto a polycarbonate plate at Cartesian coordinates (every five seconds). The samples were added to an enzymatic reaction that generates hydrogen peroxide from glutamate, which was quantified using fluorescence detection. Fluorescence emission was induced by laser excitation, stimulating each spot automatically, in addition to controlling the humidity, temperature and incubation time of the enzymatic reaction.
  
  
  RESULTS
  The measurement of standard glutamate concentrations was linear and could be performed in dialysis samples. This approach was used to determine the effect of the convulsant drugs bicuculline and 4-aminopyridine on the extracellular glutamate concentration. Seizure activity was associated with a considerable increase in glutamate that correlated with altered EEG patterns for both drugs.
  
  
  CONCLUSIONS
  These results indicate that this method is able to read samples with high temporal resolution, and it is easy to use compared with classical methods such as high-performance liquid chromatography, with the advantage that a large number of samples can be measured in a single experimental series. This method provides an alternative approach to determine the concentrations of neurotransmitters or other compounds that generate hydrogen peroxide as a reaction product.
authors.affiliation: Laboratory of Neurophysiology and Neurochemistry, Department of Cellular and Molecular Biology, CUCBA, University of Guadalajara, Jalisco, Mexico. lauramedcej@gmail.com.
authors.forename: Laura
authors.initials: L
authors.lastname: Medina-Ceja
authors.affiliation: Laboratory of Neurophysiology and Neurochemistry, Department of Cellular and Molecular Biology, CUCBA, University of Guadalajara, Jalisco, Mexico. keny_02pp@hotmail.com.
authors.forename: Kenia
authors.initials: K
authors.lastname: Pardo-Peña
authors.affiliation: Laboratory of Neurophysiology and Neurochemistry, Department of Cellular and Molecular Biology, CUCBA, University of Guadalajara, Jalisco, Mexico. amorales@cucba.udg.mx.|Laboratorio de Neurofisiología y Neuroquímica, Departamento de Biología Celular y Molecular, Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Camino Ing. R. Padilla Sánchez 2100, Las Agujas, Nextipac, CP 45110, Zapopan, Jalisco, Mexico. amorales@cucba.udg.mx.
authors.forename: Alberto
authors.initials: A
authors.lastname: Morales-Villagrán
authors.affiliation: Laboratory of Neurophysiology and Neurochemistry, Department of Cellular and Molecular Biology, CUCBA, University of Guadalajara, Jalisco, Mexico. venomjmo@hotmail.com.mx.
authors.forename: Jorge
authors.initials: J
authors.lastname: Ortega-Ibarra
authors.affiliation: Laboratory of Neurophysiology and Neurochemistry, Department of Cellular and Molecular Biology, CUCBA, University of Guadalajara, Jalisco, Mexico. sjlopez@cucba.udg.mx.
authors.forename: Silvia
authors.initials: S
authors.lastname: López-Pérez
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002138:Calibration; D002408:Catheters, Indwelling; D003292:Convulsants / Q000494:pharmacology; D003956:Dialysis / Q000379:methods*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004867:Equipment Design; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D005453:Fluorescence; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007834:Lasers; D008297:Male; D017208:Rats, Wistar; D012640:Seizures / Q000378:metabolism*
chemical_list: D003292:Convulsants; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D015761:4-Aminopyridine; D001640:Bicuculline