GABAergic projections from the hippocampus to the retrosplenial cortex in the rat

Miyashita, Toshio; Rockland, Kathleen S.

doi:10.1111/j.1460-9568.2007.05745.x

Cited by 96 publications

(109 citation statements)

References 47 publications

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“…Second, longrange axons of nonpyramidal neurons of the CA1 region project to the medial septum, CA3, dentate gyrus, indusium griseum, and retrosplenial cortex (i.e., regions not innervated by the CA1 pyramidal cells). The GABAergic projection to the retrosplenial cortex may be particularly extensive as revealed independently from our study by retrograde labeling (Miyashita and Rockland, 2007). These findings show that long-range interneurons are involved in specialized functions not delivered by the principal cells.…”

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confidence: 55%

Neuronal Diversity in GABAergic Long-Range Projections from the Hippocampus

Jinno¹,

Klausberger²,

Márton³

et al. 2007

J. Neurosci.

319

382

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The formation and recall of sensory, motor, and cognitive representations require coordinated fast communication among multiple cortical areas. Interareal projections are mainly mediated by glutamatergic pyramidal cell projections; only few long-range GABAergic connections have been reported. Using in vivo recording and labeling of single cells and retrograde axonal tracing, we demonstrate novel long-range GABAergic projection neurons in the rat hippocampus: (1) somatostatin-and predominantly mGluR1␣-positive neurons in stratum oriens project to the subiculum, other cortical areas, and the medial septum; (2) neurons in stratum oriens, including somatostatin-negative ones; and (3) trilaminar cells project to the subiculum and/or other cortical areas but not the septum. These three populations strongly increase their firing during sharp wave-associated ripple oscillations, communicating this network state to the septotemporal system. Finally, a large population of somatostatin-negative GABAergic cells in stratum radiatum project to the molecular layers of the subiculum, presubiculum, retrosplenial cortex, and indusium griseum and fire rhythmically at high rates during theta oscillations but do not increase their firing during ripples. The GABAergic projection axons have a larger diameter and thicker myelin sheet than those of CA1 pyramidal cells. Therefore, rhythmic IPSCs are likely to precede the arrival of excitation in cortical areas (e.g., subiculum) that receive both glutamatergic and GABAergic projections from the CA1 area. Other areas, including the retrosplenial cortex, receive only rhythmic GABAergic CA1 input. We conclude that direct GABAergic projections from the hippocampus to other cortical areas and the septum contribute to coordinating oscillatory timing across structures.

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mentioning

confidence: 55%

Neuronal Diversity in GABAergic Long-Range Projections from the Hippocampus

Jinno¹,

Klausberger²,

Márton³

et al. 2007

J. Neurosci.

319

382

View full text Add to dashboard Cite

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“…Neurons expressing ENK have not been described among the extrahippocampal projecting GABAergic populations (Blasco-Ibáñez et al, 1998; Jinno and Kosaka, 2002; Miyashita and Rockland, 2007). Their identity as projection neurons is now clearly established by retrograde labeling and the corroborative features of the ENK-expressing cell recorded and labeled in vivo .…”

Section: Discussionmentioning

confidence: 99%

Rhythmically Active Enkephalin-Expressing GABAergic Cells in the CA1 Area of the Hippocampus Project to the Subiculum and Preferentially Innervate Interneurons

et al. 2008

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Enkephalins (ENKs) are endogenous opioids that regulate synaptic excitability of GABAergic networks in the cerebral cortex. Using retrograde tracer injections in the subiculum, we identified a hippocampal population of ENK-expressing projection neurons. In situ hybridization for GAD shows that ENK-expressing cells are a small GABAergic subpopulation. Furthermore, by extracellular recording and juxtacellular labeling in vivo, we identified an ENK-expressing cell in stratum radiatum of the CA1 area by its complete axodendritic arborization and characteristic spike timing during network oscillations. The somatodendritic membrane was immunopositive for mGluR1␣, and there was both a rich local axon in CA1 and subicular-projecting branches. The boutons showed cell-type-and layerspecific innervation, i.e., interneurons were the main targets in the alveus, both interneurons and pyramidal cell dendrites were innervated in the other layers, and interneurons were exclusive targets in the subiculum. Parvalbumin-, but not somatostatin-, calbindin-, or cholecystokinin-expressing interneurons were preferred synaptic targets. During network activity, the juxtacellularly labeled ENKexpressing cell was phase modulated throughout theta oscillations, but silenced during sharp-wave/ripple episodes. After these episodes the interneuron exhibited rebound activity of high-frequency spike bursts, presumably causing peptide release. The ENK-expressing interneurons innervating parvalbumin-positive interneurons might contribute to the organization of the sharp-wave/ripple episodes by decreased firing during and rebound activity after the ripple episodes, as well as to the coordination of activity between the CA1 and subicular areas during network oscillations.

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“…The Sub provides a meager projection to the anterior cingulate cortex (area 24; White et al, 1990) whereas the projection to the retrosplenial cortex is substantial Van Groen and Wyss, 2003;Miyashita and Rockland, 2007; for an overview, see Sugar et al, 2011). The subiculoretrosplenial projection terminates predominantly in layers II and III with a modest innervation of layer IV.…”

Section: Efferentsmentioning

confidence: 98%