Age-related changes in the dynamics of potassium-evoked L-glutamate release in the striatum of Fischer 344 rats

Abstract

In the present studies we used a multisite ceramic-based microelectrode for rapid (800 ms) and low level measures of L-glutamate in vivo. We measured the amplitude and clearance rate of phasic changes in L-glutamate release produced by local application of potassium by a micropipette placed adjacent to the recording sites in the striatum of young (6 month), late middle aged (18 month) and aged (24 month) Fischer 344 rats. Our results showed that the amplitudes and clearance rates of potassium-evoked release of L-glutamate in the striatum were significantly decreased in aged rats as compared to the other age groups. In addition, the sensitivity of glutamate fibers to depolarization with potassium was significantly decreased in the aged rats as compared to young animals. Taken together, these data are consistent with age-related alterations in glutamate release dynamics, which may involve a compensatory mechanism for maintaining static glutamate concentrations within the striatum.

Second-by-Second Measures of l-Glutamate in the Prefrontal Cortex and Striatum of Freely Moving Mice

“…Ceramic-based MEAs were assembled and prepared for in vivo recordings as described previously (Burmeister et al, 2000(Burmeister et al, , 2002Nickell et al, 2005;Hascup et al, 2006;Rutherford et al, 2007). The four platinum recording sites were dip-coated with Nafion (Sigma-Aldrich, St. Louis, MO) to repel anions such as DOPAC and AA (Burmeister and Gerhardt, 2001).…”

“…Our laboratory has developed an enzyme-based microelectrode array (MEA) that is capable of detecting low levels of Glu on a subsecond time scale (500 -800 ms) that is free from central nervous system interferents such as 3,4-dihydroxyphenylacetic acid (DOPAC) and ascorbic acid (AA) (Burmeister and Gerhardt, 2001;Burmeister et al, 2002). These MEAs have been successfully used by our laboratory to measure Glu dynamics in anesthetized and awake Fischer 344 rats (Nickell et al, 2005;Day et al, 2006;Rutherford et al, 2007). The present study concerns the adaptation and validation of these MEAs for selective Glu recordings in awake, freely moving mice.…”

Resting Glutamate Levels and Rapid Glutamate Transients in the Prefrontal Cortex of the Flinders Sensitive Line Rat: A Genetic Rodent Model of Depression

“…Briefly, the platinum recording sites were dip coated with Nafion (Sigma-Aldrich, St Louis, MO) to repel anions (Burmeister and Gerhardt, 2001). Two of the MEA recording sites were coated with an L-glutamate oxidase (EC 1.4.3.11) (Seikagaku America, East Falmouth, MA) coating solution (Nickell et al, 2005). To induce crosslinking of L-glutamate oxidase and to increase the adhesion to the microelectrode, glutaraldehyde, and BSA (Sigma-Aldrich) were added to the L-glutamate oxidase solution.…”

“…MEAs were calibrated to determine their sensitivity and selectivity against ascorbic acid as previously described (Hascup et al, 2010(Hascup et al, , 2009(Hascup et al, , 2008(Hascup et al, , 2006Nickell et al, 2005). Selectivity ratios for glutamate over ascorbic acid were calculated in addition to the slope (sensitivity), limit of detection (LOD), and linearity (R 2 ) for glutamate for all MEAs.…”

Decreased Dopamine D4 Receptor Expression Increases Extracellular Glutamate and Alters Its Regulation in Mouse Striatum

“…Ceramicbased microelectrode arrays (MEAs) that contained four platinum (Pt) recording surfaces were prepared to selectively measure Glu (Figure 1a). These electrodes were fabricated for in vivo recordings using published methods (Burmeister et al, 2000(Burmeister et al, , 2002Nickell et al, 2005). All four sites were electroplated with meta-phenylenediamine (mPD) by applying a potential of + 0.5 V to the Pt sites vs a silver/silver chloride (Ag/AgCl) reference electrode (Bioanalytical Systems, RE-5) in a deoxygenated 0.05 M phosphate-buffered saline (PBS, pH 7.1-7.4) with 5.0 mM mPD.…”