Dopamine is a critical determinant of neostriatal function, but its impact on intrastriatal GABAergic signaling is poorly understood. The role of D(1) dopamine receptors in the regulation of postsynaptic GABA(A) receptors was characterized using whole cell voltage-clamp recordings in acutely isolated, rat neostriatal medium spiny neurons. Exogenous application of GABA evoked a rapidly desensitizing current that was blocked by bicuculline. Application of the D(1) dopamine receptor agonist SKF 81297 reduced GABA-evoked currents in most medium spiny neurons. The D(1) dopamine receptor antagonist SCH 23390 blocked the effect of SKF 81297. Membrane-permeant cAMP analogues mimicked the effect of D(1) dopamine receptor stimulation, whereas an inhibitor of protein kinase A (PKA; Rp-8-chloroadenosine 3',5' cyclic monophosphothioate) attenuated the response to D(1) dopamine receptor stimulation or cAMP analogues. Inhibitors of protein phosphatase 1/2A potentiated the modulation by cAMP analogues. Single-cell RT-PCR profiling revealed consistent expression of mRNA for the beta1 subunit of the GABA(A) receptor-a known substrate of PKA-in medium spiny neurons. Immunoprecipitation assays of radiolabeled proteins revealed that D(1) dopamine receptor stimulation increased phosphorylation of GABA(A) receptor beta1/beta3 subunits. The D(1) dopamine receptor-induced phosphorylation of beta1/beta3 subunits was attenuated significantly in neostriata from DARPP-32 mutants. Voltage-clamp recordings corroborated these results, revealing that the efficacy of the D(1) dopamine receptor modulation of GABA(A) currents was reduced in DARPP-32-deficient medium spiny neurons. These results argue that D(1) dopamine receptor stimulation in neostriatal medium spiny neurons reduces postsynaptic GABA(A) receptor currents by activating a PKA/DARPP-32/protein phosphatase 1 signaling cascade targeting GABA(A) receptor beta1 subunits.

Regulator of G protein signaling (RGS) proteins negatively regulate receptor-mediated second messenger responses by enhancing the GTPase activity of G␣ subunits. We describe a receptor-specific role for an RGS protein at the level of an individual brain neuron. RGS9-2 and G␤5 mRNA and protein complexes were detected in striatal cholinergic and ␥-aminobutyric acidergic neurons. Dialysis of cholinergic neurons with RGS9 constructs enhanced basal Ca 2؉ channel currents and reduced D2 dopamine receptor modulation of Cav2.2 channels. These constructs did not alter M2 muscarinic receptor modulation of Cav2.2 currents in the same neuron. The noncatalytic DEP-GGL domain of RGS9 antagonized endogenous RGS9-2 activity, enhancing D2 receptor modulation of Ca 2؉ currents. In vitro, RGS9 constructs accelerated GTPase activity, in agreement with electrophysiological measurements, and did so more effectively at Go than Gi. These results implicate RGS9-2 as a specific regulator of dopamine receptor-mediated signaling in the striatum and identify a role for GAP activity modulation by the DEP-GGL domain.calcium ͉ GTPase activating protein ͉ receptor-specific ͉ basal ganglia ͉ indirect pathway R egulators of G protein signaling (RGS) are a diverse family of proteins identified by the presence of a 120-aa domain termed the RGS box. In cell lines or in purified in vitro assays, most RGS proteins enhance the GTPase activity of heterotrimeric G protein ␣ subunits and thereby accelerate the deactivation of receptor-initiated second messenger responses. Many RGS proteins also contain one or more putative protein-protein interaction domains. These noncatalytic domains have been suggested to regulate catalytic activity, signal transduction pathway specificity, and͞or subcellular targeting of RGS proteins.One subfamily of RGS proteins (RGS6, -7, -9, and -11) all share homologous DEP (Dishevelled, Egl-10, Pleckstrin), GGL (G protein Gamma subunit Like), and RGS domains. The DEP domain of the retinal isoform of RGS9 (RGS9-1) has been shown to confer localization to a retinal membrane protein termed R9AP, and this localization has been shown to be necessary for proper RGS9-1 function in the retina (1). Several investigators have demonstrated that the GGL domain interacts with the G␤ 5 subunit (2-6). In vitro, G␤ 5 binding to RGS6, -7, or -11 increases the GAP specificity of these RGS proteins for G␣ (2, 3). In addition, G␤ 5 binding to either RGS7 or RGS9 enhances RGS-mediated acceleration of G protein gated inwardly rectifying K ϩ (Kir3) channel activation and deactivation kinetics in an oocyte expression system. This enhancement may result from G␤ 5 -mediated increased stability of the RGS protein or enhanced GAP activity (7).Despite the functional similarities among RGS6, -7, -9, and -11 in heterologous expression systems or when analyzed in vitro, each of these RGS proteins is likely to play a unique role in the central nervous system because they are differentially localized within the brain (8, 9). In contrast to the more ubiquitous loc...

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ObjectiveTo evaluate the accuracy and precision of HemoCue 201 (HemoCue) and Masimo Pronto 7 (Masimo) devices for measuring hemoglobin (Hb) in epidemiological studies, having venous blood samples as a gold standard.Material and methodsWe measured Hb concentrations in a field sample of 148 children from one to five years of age. Masimo and HemoCue were used for capillary blood samples and an automatic analyzer for venous blood samples. Regression models with no intercept were constructed to measure precision and predictability, concordance correlations to measure accuracy and precision, and Bland-Altman limits of agreement as well as hierarchical linear models to estimate variance.ResultsBoth HemoCue and Masimo underestimated Hb concentrations compared to the gold standard. They respectively yielded the following results: regression coefficients of 0.887 and 0.876 with 98.7% and 98.6% predictability; concordance correlation coefficients of 0.183 (p<0.001) and 0.166 (p<0.001); and Bland-Altman variances of -1.51 and -1.62. With regard to Masimo specifically, the three-level Hierarchical Linear Model showed that 57.9% of total variance stemmed from random errors in repeated measures from the same subject.ConclusionsHemoCue and Masimo measure lower Hb concentrations than the gold standard. Their accuracy and precision levels are comparable. It is essential to ensure proper use of devices through enhanced training of field workers.

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