Distribution of glycinergic terminals on lumbar motoneurons of the adult cat: an ultrastructural study

Destombes, J.; Horcholle‐Bossavit, G.; Thiesson, D.

doi:10.1016/0006-8993(92)90412-3

Cited by 31 publications

(14 citation statements)

References 33 publications

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“…This observation presumably reflects the comparably weaker glycinergic input received by ␥MNs (reviewed in Baldissera et al, 1981; see also Ellaway and Murphy, 1981; Appelberg et al, 1983a-d). Correspondingly, immunocytochemically detected glycinergic terminals have been found more frequently over the cell somas of cat lumbar ␣MNs vs. ␥MNs (Destombes et al, 1992). It is interesting that our finding of a higher density of gephyrin clusters in approximately one-half of the injected ␥MNs parallels Ellaway and Murphy's (1981) findings of recurrent inhibition in 54% of recorded ␥MNs, compared to 91% of ␣MNs.…”

Section: Cell-type Specific Patterns Of Gephyrin/glycine Receptor Clusupporting

confidence: 58%

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

et al. 1997

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Glycinergic synapses play a major role in shaping the activity of spinal cord neurons. The spatial organization of postsynaptic receptors is likely to determine many functional parameters at these synapses and is probably related to the integrative capabilities of different neurons. In the present study, we have investigated the organization of gephyrin expression along the dendritic membranes of alpha- and gamma-motoneurons, Ia inhibitory interneurons, and Renshaw cells. Gephyrin is a protein responsible for the postsynaptic clustering of glycine receptors, and the features of gephyrin and glycine receptor alpha(1)-subunit immunofluorescent clusters displayed similar characteristics on ventral horn spinal neurons. However, the density of clusters and their topographical organization and architecture varied widely in different neurons and in different dendritic regions. For motoneurons and Ia inhibitory interneurons, cluster size and complexity increased with distance from the soma, perhaps as a mechanism to enhance the influence of distal synapses. Renshaw cells were special in that they displayed an abundant complement of large and morphologically complex clusters concentrated in their somas and proximal dendrites. Serial electron microscopy confirmed that the various immunoreactivity patterns observed with immunofluorescence accurately parallel the variable organization of pre- and postsynaptic active zones of glycinergic synapses. Finally, synaptic boutons from single-labeled axons of glycinergic neurons (Ia inhibitory interneurons) were also associated with postsynaptic receptor clusters of variable shapes and configurations. Our results indicate that mechanisms regulating receptor clustering do so primarily in the context of the postsynaptic neuron identity and localization in the dendritic arbor.

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Section: Cell-type Specific Patterns Of Gephyrin/glycine Receptor Clusupporting

confidence: 58%

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

et al. 1997

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“…They contain flattened or pleomorphic vesicles (i.e., F or P type boutons) and form symmetrical synaptic active zones characteristic of inhibitory terminals (Helfert et al, 1992;Ö rnung et al, 1996;Ottersen et al, 1988;Todd, 1990;Van den Pol and Gorcs, 1988;Wentzel et al, 1993;). However, in a few studies where quantitative analysis of large samples of terminals was performed (Cabot et al, 1992;Clements et al, 1990;Destombes et al, 1992;Holstege and Bongers, 1992;Yang et al, 1997) small proportions (Ͻ10%) of glycine-IR boutons containing rounded vesicles and forming asymmetrical active zones were also detected. Such ''S-type'' boutons are generally considered to be excitatory (Uchizono, 1965).…”

Section: Structural Characteristics Of Glycine-ir Terminalsmentioning

confidence: 98%

Glycine-immunoreactive synaptic terminals in the nucleus tractus solitarii of the cat: Ultrastructure and relationship to GABA-immunoreactive terminals

Saha

Batten

McWilliam

1999

Synapse

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Postembedding immunogold labeling methods applied to ultrathin and semithin sections of cat dorsomedial medulla showed that neuronal perikarya, dendrites, myelinated and nonmyelinated axons, and axon terminals in the nucleus tractus solitarii contain glycine immunoreactivity. Light microscopic observations on semithin sections revealed that these immunoreactive structures were unevenly distributed throughout the entire nucleus. At the electron microscopic level, synaptic terminals with high levels of glycine-immunoreactivity, assumed to represent those releasing glycine as a neurotransmitter, were discriminated from terminals containing low, probably metabolic levels of glycine-immunoreactivity, by a quantitative analysis method. This compared the immunolabeling of randomly sampled terminals with a reference level of labeling derived from sampling the perikarya of dorsal vagal neurones. The vast majority of these "glycinergic" terminals contained pleomorphic vesicles, formed symmetrical synaptic active zones, and targeted dendrites. They appeared to be more numerous in areas of the nucleus tractus solitarii adjoining the tractus solitarius, but rather scarce caudally, medially, ventrally, and in the dorsal motor vagal nucleus. In a random analysis of the entire nucleus tractus solitarii, 26.2% of sampled terminals were found to qualify as glycine-immunoreactive. In contrast, boutons immunoreactive for gamma-aminobutyric acid (GABA) were more evenly distributed throughout the dorsal vagal complex and accounted for 33.7% of the synaptic terminals sampled. A comparison of serial ultrathin sections suggested three subpopulations of synaptic terminals: one containing high levels of both GABA- and glycine-immunoreactivities (21% of all terminals sampled), one containing only GABA-immunoreactivity (12.7%), and relatively few terminals (5.2%) that were immunoreactive for glycine alone. These results were confirmed by dual labeling of sections using gold particles of different sizes. This study reports the first analysis of the ultrastructure of glycinergic nerve terminals in the cat dorsal vagal complex, and the pattern of coexistence of glycine and GABA observed provides an anatomical explanation for our previously reported inhibitory effects of glycine and GABA on neurones with cardiovascular and respiratory functions in the nucleus tractus solitarii.

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“…There is a consensus that axon terminals with these structural features correspond to excitatory and inhibitory synapses, respectively (Peters and Palay, 1996). In the specific context of synapses in the ventral horn, there is widespread evidence for this structure-function correlation (e.g., for Group Ia afferents see Conradi et al, 1983;Maxwell and Bannatyne, 1983;Fyffe and Light, 1984;Nicol and Walmsley, 1991;Pierce and Mendell, 1993; for inhibitory connections see McLaughlin et al, 1975;Holstege and Calkoen, 1990;Destombes et al, 1992;Fyffe, 1991;Tai and Goshgarian, 1996;Murphy et al, 1966;Ornung et al, 1998;see, however, Rastad, 1981). Based on this correlation, the results of the present suggest that ipsilateral LVN projections to lamina IX and ventral lamina VIII are predominately excitatory.…”

Section: Classification Of Axon Terminalsmentioning

confidence: 95%

Projections from the lateral vestibular nucleus to the upper cervical spinal cord of the cat: A correlative light and electron microscopic study of axon terminals stained with PHA‐L

et al. 1999

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Distribution of glycinergic terminals on lumbar motoneurons of the adult cat: an ultrastructural study

Cited by 31 publications

References 33 publications

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

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

Glycine-immunoreactive synaptic terminals in the nucleus tractus solitarii of the cat: Ultrastructure and relationship to GABA-immunoreactive terminals

Projections from the lateral vestibular nucleus to the upper cervical spinal cord of the cat: A correlative light and electron microscopic study of axon terminals stained with PHA‐L

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