Cell‐type specific organization of glycine receptor clusters in the mammalian spinal cord

Álvarez, Francisco J.; Dewey, Dianne E.; Harrington, Deborah A.; Fyffe, Robert E.W.

doi:10.1002/(sici)1096-9861(19970303)379:1<150::aid-cne10>3.3.co;2-m

Cited by 49 publications

(105 citation statements)

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“…Although we did not specifically search for other target cells of glycinergic interneurons, we noted that some of them made contact with cells that were rich in gephyrin and were located at the border of laminae VII and IX. These cells are in a similar location to Renshaw cells which are also rich in gephyrin (Alvarez et al 1997). However, the pattern of gephyrin labelling associated with cells described here appears to differ from that described by Alvarez et al who showed that Renshaw cells are associated with intense rings of immunoreactivity (see their Fig.…”

Section: Table 2 Distribution Of Monosynaptic Excitatory and Inhibitsupporting

confidence: 50%

Excitatory and inhibitory intermediate zone interneurons in pathways from feline group I and II afferents: differences in axonal projections and input

Bannatyne

Liu

Hammar

et al. 2009

The Journal of Physiology

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The aim of the present study was to compare properties of excitatory and inhibitory spinal intermediate zone interneurons in pathways from group I and II muscle afferents in the cat. Interneurons were labelled intracellularly and their transmitter phenotypes were defined by using immunocytochemistry. In total 14 glutamatergic, 22 glycinergic and 2 GABAergic/ glycinergic interneurons were retrieved. All interneurons were located in laminae V-VII of the L3-L7 segments. No consistent differences were found in the location, the soma sizes or the extent of the dendritic trees of excitatory and inhibitory interneurons. However, major differences were found in their axonal projections; excitatory interneurons projected either ipsilaterally, bilaterally or contralaterally, while inhibitory interneurons projected exclusively ipsilaterally. Terminal projections of glycinergic and glutamatergic cells were found within motor nuclei as well as other regions of the grey matter which include the intermediate region, laminae VII and VIII. Cells containing GABA/glycine had more restricted projections, principally within the intermediate zone where they formed appositions with glutamatergic axon terminals and unidentified cells and therefore are likely to be involved in presynaptic as well as postsynaptic inhibition. The majority of excitatory and inhibitory interneurons were found to be coexcited by group I and II afferents (monosynaptically) and by reticulospinal neurons (mono-or disynaptically) and to integrate information from several muscles. Taken together the morphological and electrophysiological data show that individual excitatory and inhibitory intermediate zone interneurons may operate in a highly differentiated way and thereby contribute to a variety of motor synergies.

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Section: Table 2 Distribution Of Monosynaptic Excitatory and Inhibitsupporting

confidence: 50%

Excitatory and inhibitory intermediate zone interneurons in pathways from feline group I and II afferents: differences in axonal projections and input

Bannatyne

Liu

Hammar

et al. 2009

The Journal of Physiology

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“…A contribution from phasic excitation is certain, from the motoneurons known to be active with respiration. But then Renshaw cells are known to receive substantial inhibitory inputs, as shown physiologically (Wilson et al 1964;Ryall 1970) and anatomically (Alvarez et al 1997). However, the extent to which that inhibition is phasic with respiration (e.g., from other Renshaw cells) remains still unclear.…”

Section: Discussionmentioning

confidence: 99%

Axonal projections of Renshaw cells in the thoracic spinal cord

Saywell¹,

Ford

Kirkwood

2013

Physiol Rep

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Renshaw cells are widely distributed in all segments of the spinal cord, but detailed morphological studies of these cells and their axonal branching patterns have only been made for lumbosacral segments. For these, a characteristic distribution of terminals was reported, including extensive collateralization within 1–2 mm of the soma, but then more restricted collaterals given off at intervals from the funicular axon. Previous authors have suggested that the projections close to the soma serve inhibition of motoneurons (known to be greatest for the motor nuclei providing the Renshaw cell excitation) but that the distant projections serve mainly the inhibition of other neurons. However, in thoracic segments, inhibition of motoneurons is known to occur over two to three segments (20–40 mm) from the presumed somatic locations of the Renshaw cells. Here, we report the first detailed morphological study of Renshaw cell axons outside the lumbosacral segments, which investigated whether this different distribution of motoneuron inhibition is reflected in a different pattern of Renshaw cell terminations. Four Renshaw cells in T7 or T8 segments were intracellularly labeled with neurobiotin in anesthetized cats and their axons traced for distances ≥6 mm from the somata. The only morphological difference detected within this distance in comparison with Renshaw cells in the lumbosacral cord was a minimal taper in the funicular axons, where in the lumbosacral cord this is pronounced. Patterns of termination were virtually identical to those in the lumbosacral segments, so we conclude that these patterns are unrelated to the pattern of motoneuronal inhibition.

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“…Since Kv2.1-IR is widespread in the ventral horn, it was of interest to determine if these channels are expressed by interneuronal populations as well as by α-motoneurones. Renshaw cells in ventral lamina VII can be easily identified by their gephyrin-IR (present at postsynaptic glycine/GABA synapses) and by calbindin d28K expression (see Alvarez et al 1997;Carr et al 1998). Dual immunolabelling demonstrated that Renshaw cells exhibit little or no Kv2.1-IR (Fig.…”

Section: Kv21 Channel Immunolabelling and Organization In Interneuronesmentioning

confidence: 99%

Focal aggregation of voltage‐gated, Kv2.1 subunit‐containing, potassium channels at synaptic sites in rat spinal motoneurones

Muennich

Fyffe

2004

The Journal of Physiology

101

176

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Delayed rectifier K+ currents are involved in the control of α-motoneurone excitability, but the precise spatial distribution and organization of the membrane ion channels that contribute to these currents have not been defined. Voltage-activated Kv2.1 channels have properties commensurate with a contribution to delayed rectifier currents and are expressed in neurones throughout the mammalian central nervous system. A specific antibody against Kv2.1 channel subunits was used to determine the surface distribution and clustering of Kv2.1 subunitcontaining channels in the cell membrane of α-motoneurones and other spinal cord neurones. In α-motoneurones, Kv2.1 immunoreactivity (-IR) was abundant in the surface membrane of the soma and large proximal dendrites, and was present also in smaller diameter distal dendrites. Plasma membrane-associated Kv2.1-IR in α-motoneurones was distributed in a mosaic of small irregularly shaped, and large disc-like, clusters. However, only small to medium clusters of Kv2.1-IR were observed in spinal interneurones and projection neurones, and some interneurones, including Renshaw cells, lacked demonstrable Kv2.1-IR. In α-motoneurones, dual immunostaining procedures revealed that the prominent disc-like domains of Kv2.1-IR are invariably apposed to presynaptic cholinergic C-terminals. Further, Kv2.1-IR colocalizes with immunoreactivity against postsynaptic muscarinic (m2) receptors at these locations. Ultrastructural examination confirmed the postsynaptic localization of Kv2.1-IR at C-terminal synapses, and revealed clusters of Kv2.1-IR at a majority of S-type, presumed excitatory, synapses. Kv2.1-IR in α-motoneurones is not directly associated with presumed inhibitory (F-type) synapses, nor is it present in presynaptic structures apposed to the motoneurone. Occasionally, small patches of extrasynaptic Kv2.1-IR labelling were observed in surface membrane apposed by glial processes. Voltage-gated potassium channels responsible for the delayed rectifier current, including Kv2.1, are usually assigned roles in the repolarization of the action potential. However, the strategic localization of Kv2.1 subunit-containing channels at specific postsynaptic sites suggests that this family of voltage-activated K + channels may have additional roles and/or regulatory components.

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Cell‐type specific organization of glycine receptor clusters in the mammalian spinal cord

Cited by 49 publications

References 0 publications

Excitatory and inhibitory intermediate zone interneurons in pathways from feline group I and II afferents: differences in axonal projections and input

Excitatory and inhibitory intermediate zone interneurons in pathways from feline group I and II afferents: differences in axonal projections and input

Axonal projections of Renshaw cells in the thoracic spinal cord

Focal aggregation of voltage‐gated, Kv2.1 subunit‐containing, potassium channels at synaptic sites in rat spinal motoneurones

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