Brain research bulletin
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Brain research bulletin · Mar 2002
NMDA and AMPA/kainate glutamatergic agonists increase the extracellular concentrations of GABA in the prefrontal cortex of the freely moving rat: modulation by endogenous dopamine.
Using microdialysis in the prefrontal cortex, this study investigated first the effects of the ionotropic glutamatergic agonists NMDA and AMPA on extracellular concentrations of GABA, and second, the modulation of these effects by increasing endogenous dopamine. NMDA (20, 100, and 500 microM) and AMPA (1, 20, and 100 microM), perfused through the microdialysis probe for 60 min, produced a dose-related increase of extracellular concentrations of GABA in the prefrontal cortex of the awake rat. NMDA 100 and 500 microM produced a maximal increase of extracellular GABA of 150 +/- 38% and 245 +/- 75% of baseline, respectively. ⋯ However, increases of endogenous dopamine at 0.5-0.7 nM did potentiate the increases of extracellular GABA produced by AMPA (20 microM) (from 140% to 240% of baseline), but not by NMDA (100 microM), in this area of the brain. These effects were attenuated by the perfusion of (-)sulpiride (D2 antagonist), but not by the perfusion of SCH-23390 (D1 antagonist). These results suggest that glutamate, through the activation of both NMDA and AMPA/kainate ionotropic receptors, facilitates GABAergic transmission in the prefrontal cortex, and that dopamine can modulate the effects of glutamate through AMPA/kainate receptors on GABA transmission in this area of the brain.
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Brain research bulletin · Mar 2002
Dynamic changes and spatial correlation of EEG activities during cold pressor test in man.
To explore the effects of tonic cold pain in man, the pain rating (intensity and distress), skin temperature, and continuous EEG recording were conducted before, during, and after cold pressor test (CPT) in 15 young healthy males. The acquired electroencephalogram (EEG) data was analysed in four ways: (1) comparison of EEG topographic patterns and power spectra across baseline, CPT, and post-CPT; (2) dynamic EEG changes during CPT; (3) correlation of EEG activities at the isolated focal maxima across the three experimental stages; and (4) spatial correlation of EEG powers among the focal sites during CPT. ⋯ This new evidence and the detailed EEG effects in CPT may enhance our understanding of the dynamics in cerebral processing of tonic noxious information. Alpha reduction may reflect the attention processing in nociceptive input, and the delta/theta/beta activation may be related to the motivational modulation of the brain.