The 5-HT1A serotonin receptor is located on calbindin- and parvalbumin-containing neurons in the rat brain

The 5-HT(1A) receptor is a well-characterized serotonin receptor playing a role in many central nervous functions and known to be involved in depression and other mental disorders. In situ hybridization, immunocytochemical, and binding studies have shown that the 5-HT(1A) receptor is widely distributed in the rat brain, with a particularly high density in the limbic system. The receptor's localization in the different neuronal subtypes, which may be of importance for understanding its role in neuronal circuitries, is, however, unknown. In this study we show by immunocytochemical double-labeling techniques, that the 5-HT(1A) receptor is present on both pyramidal and principal cells, and calbindin- and parvalbumin-containing neurons, which generally define two different subtypes of interneurons. Moreover, semiquantitative analysis showed that the receptor's distribution in the different neuronal types varies between brain areas. In cortex, hippocampus, hypothalamus, and amygdala the receptor was located on both principal cells and calbindin- and parvalbumin-containing neurons. In septum and thalamus, the receptor was mostly present on calbindin- and parvalbumin-containing cells. Especially in the medial septum and thalamic reticular nucleus, the receptor highly colocalized with parvalbumin-positive neurons. These results suggest a diverse function of the 5-HT(1A) receptor in modulating neuronal circuitry in different brain areas, that may depend on the type of neuron the receptor is predominantly located on.     

NMDA receptor blockade in intact adult cortex increases trafficking of NR2A subunits into spines,postsynaptic densities,and axon terminals

Past in vitro studies have used immunofluorescence to show increased clustering of the NR1 subunits of NMDA receptors (NMDAR) following NMDAR blockade, indicating that NMDARs self-regulate trafficking to and from spines. However, since a substantial portion of spinous NMDAR subunits can reside at sites removed from plasma membranes, whether or not these immunofluorescent clusters are synaptic remains to be shown. Also, the NR2A/B subunits undergo activity-dependent switching at synapses, indicating that their subcellular distribution may be regulated differently from the NR1 subunits. We examined the issue of NMDAR autoregulation by determining whether in vivo NMDAR blockade enhances trafficking of the NR2A subunits toward spines and more specifically to postsynaptic densities (PSDs) of already mature synapses. Seven adult rats received unilateral intra-cortical infusion of the NMDAR antagonist, D-AP5 for 1/2-2 h and the inactive enantiomer or the solvent, alone, in the contralateral cortex. Using an electron microscope, approximately 5600 cortical spines originating from the two hemispheres of the seven adult animals were analyzed for the location of NR2A subunits. In six out of the seven cases analyzed, the D-AP5-treated neuropil exhibited increased immunolabeling at PSDs and a concomitantly great increase at non-synaptic sites within spines. NR2A subunits also increased presynaptically within 1/2 h but not after 1 h. These findings indicate that NR2A subunits in intact, adult cortical neurons are prompted to become trafficked into spines and axon terminals by NMDAR inactivity, yielding an increase of a readily available reserve pool and greater localization at both sides of synapses.     

Excitotoxic lesions of the medial prefrontal cortex attenuate fear responses in the elevated-plus maze,social interaction and shock probe burying tests

Previous research investigating the effects of medial prefrontal cortex (MPFC) lesions on fear- and anxiety-related behavior has yielded an inconsistent body of findings. Behavioral studies have reported increases, decreases, and no effect on anxiety. In addition, many studies are complicated by the use of lesioning techniques that destroy fibers of passage, and the use of conditioned fear tests, which may introduce the confounding effects of learning and memory. Therefore, the present study examined the effects of ibotenic acid lesions of the MPFC (including prelimbic, infralimbic and anterior cingulate) on three wide-ranging and well-validated behavioral assays of anxiety: the elevated plus maze (EPM), social interaction (SI) and the shock-probe tests (SP). In the EPM test, lesioned rats showed a significantly higher percentage of open arm entries and open arm time than controls. In a version of the SI test sensitive to anxiolytic effects, lesioned rats were found to spend a significantly greater amount of time in active interaction with a conspecific; while another version of the SI test sensitive to anxiogenic effects did not show any differences between lesioned and non-lesioned controls. In the SP test, lesioned rats exhibited significantly lower rates of burying. In contrast, retention of shock probe avoidance was not affected. No effects of lesions on measures of locomotor activity or shock reactivity were found. The concordant anxiolytic-like effects found in the three behavioral assays strongly suggests a general reduction in fear responsiveness in MPFC lesioned rats.     

Platelet-induced expression of tissue factor procoagulant activity in freshly isolated human mononuclear cells: implications for experimental use

Monocytes express tissue factor (TF) as a result of cytokine stimulation or endothelial adherence. We evaluated monocyte-platelet interaction in vitro as another trigger for monocyte TF enhancement in human mononuclear cells isolated by density gradient centrifugation from peripheral blood. Cell TF procoagulant activity (TF-PCA) was quantitated by a one-stage recalcification clotting time assay. Platelets were counted and identified by whole blood flow cytometry as CD61 positive particles, activated platelets were characterized by P-Selectin (CD62) expression, and monocytes by surface CD14 expression. A significant correlation between normalized TF-PCA of isolated mononuclear cells and platelet count was shown (r = 0.43, P < 0.001). Percentage of activated platelets in baseline samples was 4.2 +/- 3.5 while adenosine diphosphate (ADP) increased platelet positivity to 34 +/- 17% (P < 0.001). After isolation, 52 +/- 12% of platelets within suspensions were activated (P < 0.0001). Percentage of CD62-positive monocytes (CD14+ particles) increased from baseline 5% to 13 +/- 6% in ADP-stimulated samples to 53 +/- 17% after isolation (P < 0.001). These findings suggest that density gradient centrifugation activates platelets and that an adhesive interaction between monocytes and platelets may promote TF-PCA expression in isolated mononuclear suspensions. Enhanced monocyte TF expression as a result of an activated platelet-monocyte interaction seems to be an important laboratory effect requiring consideration when utilizing this technique in an experimental setup.