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  • 1
    Keywords: IN-VIVO ; RESPONSES ; RAT STRIATUM ; NUCLEUS-ACCUMBENS ; VENTRAL TEGMENTAL AREA ; OLFACTORY TUBERCLE ; MIDBRAIN DOPAMINE ; GLUTAMATE NEURONS ; AFFERENT-FIBERS ; DORSAL STRIATUM
    Abstract: Phasic increases in dopamine (DA) are involved in the detection and selection of relevant sensory stimuli. The DAergic and cholinergic system dynamically interact to gate and potentiate sensory inputs to striatum. Striatal cholinergic interneurons (CINs) respond to relevant sensory stimuli with an initial burst, a firing pause, or a late burst, or a combination of these three components. CIN responses coincide with phasic firing of DAergic neurons in vivo. In particular, the late burst of CINs codes for the anticipated reward. To examine whether DAergic midbrain afferents can evoke the different CIN responses, we recorded from adult olfactory tubercle slices in the mouse ventral striatum. Olfactory inputs to striatal projection neurons were gated by the cholinergic tone. Phasic optogenetic activation of DAergic terminals evoked combinations of initial bursts, pauses, and late bursts in subsets of CINs by distinct receptor pathways. Glutamate release from midbrain afferents evoked an NMDAR-dependent initial burst followed by an afterhyperpolarization-induced pause. Phasic release of DA itself evoked acute changes in CIN firing. In particular, in CINs without an initial burst, phasic DA release evoked a pause through D2-type DA receptor activation. Independently, phasic DA activated a slow depolarizing conductance and the late burst through a D1-type DA receptor pathway. In summary, DAergic neurons elicit transient subsecond firing responses in CINs by sequential activation of NMDA, D2-type, and D1-type receptors. This fast control of striatal cholinergic tone by phasic DA provides a novel dynamic link of two transmitter systems central to the detection and selection of relevant stimuli.
    Type of Publication: Journal article published
    PubMed ID: 25164653
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  • 2
    Keywords: brain ; EXPRESSION ; SYSTEM ; GENES ; MICE ; DISRUPTION ; CORTEX ; autism ; NEURONAL PATTERNS ; AMPA
    Abstract: In postnatal development, GluN2B-containing NMDARs are critical for the functional maturation of glutamatergic synapses. GluN2B-containing NMDARs prevail until the second postnatal week when GluN2A subunits are progressively added, conferring mature properties to NMDARs. In cortical principal neurons, deletion of GluN2B results in an increase in functional AMPAR synapses, suggesting that GluN2B-containing NMDARs set a brake on glutamate synapse maturation. The function of GluN2B in the maturation of glutamatergic inputs to cortical interneurons is not known. To examine the function of GluN2B in interneurons, we generated mutant mice with conditional deletion of GluN2B in interneurons (GluN2B(DeltaGAD67)). In GluN2B(DeltaGAD67) mice interneurons distributed normally in cortical brain regions. After the second postnatal week, GluN2B(DeltaGAD67) mice developed hippocampal seizures and died shortly thereafter. Before the onset of seizures, GluN2B-deficient hippocampal interneurons received fewer glutamatergic synaptic inputs than littermate controls, indicating that GluN2B-containing NMDARs positively regulate the maturation of glutamatergic input synapses in interneurons. These findings suggest that GluN2B-containing NMDARs keep the circuit activity under control by promoting the maturation of excitatory synapses in interneurons.
    Type of Publication: Journal article published
    PubMed ID: 25429143
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  • 3
    Abstract: Oxytocin promotes social interactions and recognition of conspecifics that rely on olfaction in most species. The circuit mechanisms through which oxytocin modifies olfactory processing are incompletely understood. Here, we observed that optogenetically induced oxytocin release enhanced olfactory exploration and same-sex recognition of adult rats. Consistent with oxytocin's function in the anterior olfactory cortex, particularly in social cue processing, region-selective receptor deletion impaired social recognition but left odor discrimination and recognition intact outside a social context. Oxytocin transiently increased the drive of the anterior olfactory cortex projecting to olfactory bulb interneurons. Cortical top-down recruitment of interneurons dynamically enhanced the inhibitory input to olfactory bulb projection neurons and increased the signal-to-noise of their output. In summary, oxytocin generates states for optimized information extraction in an early cortical top-down network that is required for social interactions with potential implications for sensory processing deficits in autism spectrum disorders.
    Type of Publication: Journal article published
    PubMed ID: 27112498
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  • 4
    Keywords: brain ; EXPRESSION ; IN-VIVO ; synaptic plasticity ; DENTATE GYRUS ; neurogenesis ; GENERATED NEURONS ; SUBVENTRICULAR ZONE ; GRANULE CELLS ; CRITICAL PERIOD
    Abstract: In the developing telencephalon, NMDA receptors (NMDARs) are composed of GluN1 and GluN2B subunits. These "young" NMDARs set a brake on synapse recruitment in neurons of the neonatal cortex. The functional role of GluN2B for synapse maturation of adult-born granule cells (GCs) in the olfactory bulb has not been established and may differ from that of differentiating neurons in immature brain circuits with sparse activity. We genetically targeted GCs by sparse retroviral delivery in mouse subventricular zone that allows functional analysis of single genetically modified cells in an otherwise intact environment. GluN2B-deficient GCs did not exhibit impairment with respect to the first developmental milestones such as synaptogenesis, dendrite formation, and maturation of inhibitory synaptic inputs. However, GluN2B deletion prevented maturation of glutamatergic synaptic input. This severe impairment in synaptic development was associated with a decreased response to novel odors and eventually led to the demise of adult-born GCs. The effect of GluN2B on GC survival is subunit specific, since it cannot be rescued by GluN2A, the subunit dominating mature NMDAR function. Our observations indicate that, GluN2B-containing NMDARs promote synapse activation in adult-born GCs that integrate in circuits with high and correlated synaptic activity. The function of GluN2B-containing NMDARs on synapse maturation can thus be bidirectional depending on the environment.
    Type of Publication: Journal article published
    PubMed ID: 22956849
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