Excitatory Connections Made by Presynaptic Cortico-Cortical Pyramidal Cells in Layer 6 of the Neocortex

Mercer, Audrey; West, David C.; Morris, Oliver T.; Kirchhecker, Sarah; Kerkhoff, Jane E.; Thomson, Alex M.

doi:10.1093/cercor/bhi027

Cited by 104 publications

(128 citation statements)

References 25 publications

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“…Synaptic connection selectivity between pyramidal cell subtypes Pyramidal cells are functionally connected with each other by local collaterals (Thomson and Deuchars, 1994;Markram et al, 1997;Mercer et al, 2005), and pyramidal cells in different layers are selectively connected (Thomson and Bannister, 2003;Feldmeyer et al, 2005). Pyramidal cells in the same layer appear to be connected in nonrandom ways Song et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

“…Considering the interlaminar connectivity of pyramidal cells, the reverberating excitation could occur in individual cortical layers (Thomson and Morris, 2002), perhaps within layer V (Sanchez-Vives and McCormick, 2000). Although the specific synaptic connectivity of cortical projection neurons within the same layer is not yet established, recent data suggest that different classes of cortical neurons within a layer may show selective connectivity (Mercer et al, 2005), a finding that has important implications for our understanding of the function of the cortex.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Recurrent Connection Patterns of Corticostriatal Pyramidal Cells in Frontal Cortex

Morishima

Kawaguchi²

2006

J. Neurosci.

262

324

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recurrent Connection Patterns of Corticostriatal Pyramidal Cells in Frontal Cortex

Morishima

Kawaguchi²

2006

J. Neurosci.

262

324

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“…Our preliminary analysis suggested that the firing properties of the layer VI pyramidal neurons in rat could be a useful criterion to predict which neurons were likely to have nicotinic currents, as shown in Figure 2. Recent work has suggested that corticothalamic layer VI neurons are regular spiking neurons (West et al, 2006), whereas layer VI corticocortical neurons tend to be burst-spiking neurons (Mercer et al, 2005). Therefore, we compared nicotinic inward currents between regular spiking and bursting neurons from rats from ages P15 to P42.…”

Section: Nicotinic Currents In Layer VI Pyramidal Neurons Change Acromentioning

confidence: 99%

Developmental Excitation of Corticothalamic Neurons by Nicotinic Acetylcholine Receptors

Kassam¹,

Herman²,

Goodfellow³

et al. 2008

J. Neurosci.

129

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In this study, we show robust nicotinic excitation of pyramidal neurons in layer VI of prefrontal cortex. This layer contains the corticothalamic neurons, which gate thalamic activity and play a critical role in attention. Our experiments tested nicotinic excitation across postnatal development, using whole-cell recordings in prefrontal brain slices from rats. These experiments showed that layer VI neurons have peak nicotinic currents during the first postnatal month, a time period of intensive cortical development in rodents. We demonstrate that these currents are mediated directly by postsynaptic nicotinic receptors and can be suppressed by a competitive antagonist of ␣ 4 ␤ 2 * nicotinic receptors. To record from identified corticothalamic neurons, we performed stereotaxic surgery to label the neurons projecting to medial dorsal thalamus. As hypothesized, recordings from these retrogradely labeled neurons in layer VI showed prominent nicotinic currents. Finally, we examined the effects of the drug nicotine on layer VI neurons and probed for the potential involvement of the accessory subunit, ␣ 5 , in their receptors. A level of nicotine similar to that found in the blood of smokers elicits a stable inward current in layer VI neurons, yet this exposure desensitizes ϳ50% of the subsequent current elicited by acetylcholine. An allosteric modulator of ␣ 4 ␤ 2 ␣ 5 receptors resulted in a 2.5-fold potentiation of submaximal nicotinic currents. This result is consistent with the expression of the relatively rare ␣ 5 nicotinic subunit in layer VI. In summary, we show that layer VI corticothalamic neurons can be strongly excited during development by an unusual subtype of nicotinic receptor.

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“…Examination at the electron microscopic level revealed that this axon made asymmetrical synapses, as shown in the bottom left micrograph where a labeled axon terminal (a) synapses with an unlabeled dendritic spine (sp) exhibiting a postsynaptic density (arrow). (Mercer et al 2005). Finally, the neurons shown in Figs.…”

Section: Characterization Of Vglutϩ/gadϩ Nonpyramidal Neurons From Lamentioning

confidence: 99%

“…Nurr1 is expressed in layer VI neurons projecting to the ipsilateral cortex, but not those projecting to contralateral cortical regions (Arimatsu et al 2003). Although functional studies have established the existence of excitatory nonpyramidal spiny neurons in layer VI (Mercer et al 2005), the proportion of polymorphic layer VI nonpyramidal neurons displaying a glutamatergic phenotype has not been thoroughly investigated. Furthermore, relatively few reports describe the electrophysi-ological properties of layer VI spiny nonpyramidal neurons (Brumberg et al 2003;Karayannis et al 2007;Mercer et al 2005;van Brederode and Snyder 1992).…”

Section: Introductionmentioning

confidence: 99%

Glutamatergic Nonpyramidal Neurons From Neocortical Layer VI and Their Comparison With Pyramidal and Spiny Stellate Neurons

Andjelić

Gallopin²,

Cauli³

et al. 2009

Journal of Neurophysiology

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. The deeper part of neocortical layer VI is dominated by nonpyramidal neurons, which lack a prominent vertically ascending dendrite and predominantly establish corticocortical connections. These neurons were studied in rat neocortical slices using patch-clamp, single-cell reverse transcription-polymerase chain reaction, and biocytin labeling. The majority of these neurons expressed the vesicular glutamate transporter but not glutamic acid decarboxylase, suggesting that a high proportion of layer VI nonpyramidal neurons are glutamatergic. Indeed, they exhibited numerous dendritic spines and established asymmetrical synapses. Our sample of glutamatergic nonpyramidal neurons displayed a wide variety of somatodendritic morphologies and a subset of these cells expressed the Nurr1 mRNA, a marker for ipsilateral, but not commissural corticocortical projection neurons in layer VI. Comparison with spiny stellate and pyramidal neurons from other layers showed that glutamatergic neurons consistently exhibited a low occurrence of GABAergic interneuron markers and regular spiking firing patterns. Analysis of electrophysiological diversity using unsupervised clustering disclosed three groups of cells. Layer V pyramidal neurons were segregated into a first group, whereas a second group consisted of a subpopulation of layer VI neurons exhibiting tonic firing. A third heterogeneous cluster comprised spiny stellate, layer II/III pyramidal, and layer VI neurons exhibiting adaptive firing. The segregation of layer VI neurons in two different clusters did not correlate either with their somatodendritic morphologies or with Nurr1 expression. Our results suggest that electrophysiological similarities between neocortical glutamatergic neurons extend beyond layer positioning, somatodendritic morphology, and projection specificity.

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Excitatory Connections Made by Presynaptic Cortico-Cortical Pyramidal Cells in Layer 6 of the Neocortex

Cited by 104 publications

References 25 publications

Recurrent Connection Patterns of Corticostriatal Pyramidal Cells in Frontal Cortex

Recurrent Connection Patterns of Corticostriatal Pyramidal Cells in Frontal Cortex

Developmental Excitation of Corticothalamic Neurons by Nicotinic Acetylcholine Receptors

Glutamatergic Nonpyramidal Neurons From Neocortical Layer VI and Their Comparison With Pyramidal and Spiny Stellate Neurons

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