The link between dysregulated serotonergic activity and depression and anxiety disorders is well established, yet the molecular mechanisms underlying these psychopathologies are not fully understood. Here, we explore the role of microRNAs in regulating serotonergic (5HT) neuron activity. To this end, we determined the specific microRNA "fingerprint" of 5HT neurons and identified a strong microRNA-target interaction between microRNA 135 (miR135), and both serotonin transporter and serotonin receptor-1a transcripts. Intriguingly, miR135a levels were upregulated after administration of antidepressants. Genetically modified mouse models, expressing higher or lower levels of miR135, demonstrated major alterations in anxiety- and depression-like behaviors, 5HT levels, and behavioral response to antidepressant treatment. Finally, miR135a levels in blood and brain of depressed human patients were significantly lower. The current results suggest a potential role for miR135 as an endogenous antidepressant and provide a venue for potential treatment and insights into the onset, susceptibility, and heterogeneity of stress-related psychopathologies.

Mammalian bombesin-like peptides are widely distributed in the central nervous system as well as in the gastrointestinal tract, where they modulate smooth-muscle contraction, exocrine and endocrine processes, metabolism and behaviour. They bind to G-protein-coupled receptors on the cell surface to elicit their effects. Bombesin-like peptide receptors cloned so far include, gastrin-releasing peptide receptor (GRP-R), neuromedin B receptor (NMB-R), and bombesin receptor subtype-3 (BRS-3). However, despite the molecular characterization of BRS-3, determination of its function has been difficult as a result of its low affinity for bombesin and its lack of an identified natural ligand. We have generated BRS-3-deficient mice in an attempt to determine the in vivo function of the receptor. Mice lacking functional BRS-3 developed a mild obesity, associated with hypertension and impairment of glucose metabolism. They also exhibited reduced metabolic rate, increased feeding efficiency and subsequent hyperphagia. Our data suggest that BRS-3 is required for the regulation of endocrine processes and metabolism responsible for energy balance and adiposity. BRS-3-deficient mice provide a useful new model for the investigation of human obesity and associated diseases.

The molecular architecture of developing serotonin (5HT) neurons is poorly understood yet its determination is likely to be essential for elucidating functional heterogeneity of these cells and the contribution of serotonergic dysfunction to disease pathogenesis. Here, we describe the purification of postmitotic embryonic 5HT neurons by flow cytometry for whole genome microarray expression profiling of this unitary monoaminergic neuron type. Our studies identified significantly enriched expression of hundreds of unique genes in 5HT neurons thus providing an abundance of new serotonergic markers. Furthermore, we identified several hundred transcripts encoding homeodomain, axon guidance, cell adhesion, intracellular signaling, ion transport, and imprinted genes associated with various neurodevelopmental disorders that were differentially enriched in developing rostral and caudal 5HT neurons. These findings suggested a homeodomain code that distinguishes rostral and caudal 5HT neurons. Indeed, verification studies demonstrated that Hmx homeodomain and Hox gene expression defined an Hmx+ rostral subtype and Hox+ caudal subtype. Expression of engrailed genes in a subset of 5HT neurons in the rostral domain further distinguished two subtypes defined as Hmx+En+ and Hmx+En-. The differential enrichment of gene sets for different canonical pathways and gene ontology categories provided additional evidence for heterogeneity between rostral and caudal 5HT neurons. These findings demonstrate a deep transcriptome and biological pathway duality for neurons that give rise to the ascending and descending serotonergic subsystems. Our databases provide a rich, clinically relevant, resource for definition of 5HT neuron subtypes and elucidation of the genetic networks required for serotonergic function.

Glutamate transporters are essential for terminating excitatory neurotransmission. Two distinct glutamate transporters, glutamateaspartate transporter (GLAST) and excitatory amino acid transporter 4 (EAAT4), are expressed most abundantly in the molecular layer of the cerebellar cortex. GLAST is expressed in Bergmann glial processes surrounding excitatory synapses on Purkinje cell dendritic spines, whereas EAAT4 is concentrated on the extrasynaptic regions of Purkinje cell spine membranes. To clarify the functional significance of the coexistence of these transporters, we analyzed the kinetics of EPSCs in Purkinje cells of mice lacking either GLAST or EAAT4. There was no difference in the amplitude or the kinetics of the rising and initial decay phase of EPSCs evoked by stimulations of climbing fibers and parallel fibers between wild-type and EAAT4-deficient mice. However, long-lasting tail currents of the EPSCs appeared age dependently in most of Purkinje cells in EAAT4-deficient mice. These tail currents were never seen in mice lacking GLAST. In the GLAST-deficient mice, however, the application of cyclothiazide that reduces desensitization of AMPA receptors increased the peak amplitude of the EPSC and prolonged its decay more markedly than in both wild-type and EAAT4-deficient mice. The results indicate that these transporters play differential roles in the removal of synaptically released glutamate. GLAST contributes mainly to uptake of glutamate that floods out of the synaptic cleft at early times after transmitter release. In contrast, the main role of EAAT4 is to remove low concentrations of glutamate that escape from the uptake by glial transporters at late times and thus prevents the transmitter from spilling over to neighboring synapses.

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The expression of oxytocin receptor (OT-R) mRNA in the rat central nervous system was examined by in situ hybridization histochemistry using cRNA probe. Wide distribution of cells expressing OT-R mRNA was observed not only in the hypothalamus, but also in other regions. There were high levels of OT-R mRNA in the anterior olfactory nuclei, tenia tecta, olfactory tubercle, rostral most region of the frontal cortex, piriform cortex, layers 2 and 3 of the neocortex, bed nucleus of the stria terminalis, anterior medial preoptic nucleus (AV3V region), magnocellular preoptic nucleus, supraoptic nucleus, paraventricular hypothalamic nucleus, retrochiasmatic nucleus, ventromedial hypothalamic nucleus, paraventricular thalamic nucleus, central amygdaloid nucleus, medial amygdaloid nucleus, posterior cortical amygdaloid nucleus, amygdalohippocampal area, subiculum, prepositus hypoglossal nucleus, and dorsal motor nucleus of vagus. In most regions of the brain, our findings concurred with those obtained by receptor binding autoradiography using a ligand specific to OT. However, in the inferior olive nucleus, OT-R mRNA was not detected despite an abundance of binding sites showed by receptor binding autography. Despite this discrepancy OT appears to have central nervous system functions in addition to its hormonal functions.

A significant evaluation in HIF-1alpha expression was revealed in regenerating rat livers. HIF-1alpha expression was preceded by VEGF and flt-1 expression and thus may be related to sinusoidal endothelial reconstruction.