Limits...
Synaptic connectivity of the cholinergic axons in the olfactory bulb of the cynomolgus monkey.

Liberia T, Blasco-Ibáñez JM, Nácher J, Varea E, Lanciego JL, Crespo C - Front Neuroanat (2015)

Bottom Line: Our results demonstrate that the cholinergic axons form synaptic contacts on interneurons.Although the cholinergic boutons were frequently found in close vicinity of the dendrites of principal cells, we have not found synaptic contacts on them.From a comparative perspective, our data indicate that the synaptic connectivity of the cholinergic circuits is highly preserved in the OB of macrosmatic and microsmatic mammals.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Biology, Department of Cell Biology, University of Valencia Burjassot, Valencia, Spain.

ABSTRACT
The olfactory bulb (OB) of mammals receives cholinergic afferents from the horizontal limb of the diagonal band of Broca (HDB). At present, the synaptic connectivity of the cholinergic axons on the circuits of the OB has only been investigated in the rat. In this report, we analyze the synaptic connectivity of the cholinergic axons in the OB of the cynomolgus monkey (Macaca fascicularis). Our aim is to investigate whether the cholinergic innervation of the bulbar circuits is phylogenetically conserved between macrosmatic and microsmatic mammals. Our results demonstrate that the cholinergic axons form synaptic contacts on interneurons. In the glomerular layer, their main targets are the periglomerular cells, which receive axo-somatic and axo-dendritic synapses. In the inframitral region, their main targets are the granule cells, which receive synaptic contacts on their dendritic shafts and spines. Although the cholinergic boutons were frequently found in close vicinity of the dendrites of principal cells, we have not found synaptic contacts on them. From a comparative perspective, our data indicate that the synaptic connectivity of the cholinergic circuits is highly preserved in the OB of macrosmatic and microsmatic mammals.

No MeSH data available.


Related in: MedlinePlus

Absence of perisomatic synaptic contacts from VAChT-containing boutons on external tufted cells. (A) Low-power magnification view of the periglomerular region of the glomerular layer under electron microscopy showing VAChT-containing boutons close to the soma of an external tufted cell (T; dotted line). The square bouton is magnified in the panel (B). (B) The VAChT-containing bouton does not form synaptic contacts on the soma of the external tufted cell. Glial lamellae separate the plasma membranes of the VAChT-containing axon and the external tufted cell (arrows). Scale bar: 2 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4362316&req=5

Figure 5: Absence of perisomatic synaptic contacts from VAChT-containing boutons on external tufted cells. (A) Low-power magnification view of the periglomerular region of the glomerular layer under electron microscopy showing VAChT-containing boutons close to the soma of an external tufted cell (T; dotted line). The square bouton is magnified in the panel (B). (B) The VAChT-containing bouton does not form synaptic contacts on the soma of the external tufted cell. Glial lamellae separate the plasma membranes of the VAChT-containing axon and the external tufted cell (arrows). Scale bar: 2 μm.

Mentions: Electron microscopy examination demonstrated that the VAChT-containing axons formed axo-dendritic and axo-somatic synaptic contacts on some bulbar neurons. The vast majority of the cholinergic synapses did not show evident electron-dense postsynaptic thickenings. Therefore, they were classified morphologically as symmetrical synapses (Figures 4, 6–8, 9A,B). However, few synaptic contacts showed an ambiguous postsynaptic thickening and their symmetric or asymmetric nature was doubtful (Figures 9C,D). The DAB-precipitate filled up the VAChT-containing axons and thus hampered a detailed analysis of their ultrastructural features. However, presynaptic boutons containing numerous medium-sized to large round synaptic vesicles and some mitochondria were clearly observed (Figures 4, 6–9).


Synaptic connectivity of the cholinergic axons in the olfactory bulb of the cynomolgus monkey.

Liberia T, Blasco-Ibáñez JM, Nácher J, Varea E, Lanciego JL, Crespo C - Front Neuroanat (2015)

Absence of perisomatic synaptic contacts from VAChT-containing boutons on external tufted cells. (A) Low-power magnification view of the periglomerular region of the glomerular layer under electron microscopy showing VAChT-containing boutons close to the soma of an external tufted cell (T; dotted line). The square bouton is magnified in the panel (B). (B) The VAChT-containing bouton does not form synaptic contacts on the soma of the external tufted cell. Glial lamellae separate the plasma membranes of the VAChT-containing axon and the external tufted cell (arrows). Scale bar: 2 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4362316&req=5

Figure 5: Absence of perisomatic synaptic contacts from VAChT-containing boutons on external tufted cells. (A) Low-power magnification view of the periglomerular region of the glomerular layer under electron microscopy showing VAChT-containing boutons close to the soma of an external tufted cell (T; dotted line). The square bouton is magnified in the panel (B). (B) The VAChT-containing bouton does not form synaptic contacts on the soma of the external tufted cell. Glial lamellae separate the plasma membranes of the VAChT-containing axon and the external tufted cell (arrows). Scale bar: 2 μm.
Mentions: Electron microscopy examination demonstrated that the VAChT-containing axons formed axo-dendritic and axo-somatic synaptic contacts on some bulbar neurons. The vast majority of the cholinergic synapses did not show evident electron-dense postsynaptic thickenings. Therefore, they were classified morphologically as symmetrical synapses (Figures 4, 6–8, 9A,B). However, few synaptic contacts showed an ambiguous postsynaptic thickening and their symmetric or asymmetric nature was doubtful (Figures 9C,D). The DAB-precipitate filled up the VAChT-containing axons and thus hampered a detailed analysis of their ultrastructural features. However, presynaptic boutons containing numerous medium-sized to large round synaptic vesicles and some mitochondria were clearly observed (Figures 4, 6–9).

Bottom Line: Our results demonstrate that the cholinergic axons form synaptic contacts on interneurons.Although the cholinergic boutons were frequently found in close vicinity of the dendrites of principal cells, we have not found synaptic contacts on them.From a comparative perspective, our data indicate that the synaptic connectivity of the cholinergic circuits is highly preserved in the OB of macrosmatic and microsmatic mammals.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Biology, Department of Cell Biology, University of Valencia Burjassot, Valencia, Spain.

ABSTRACT
The olfactory bulb (OB) of mammals receives cholinergic afferents from the horizontal limb of the diagonal band of Broca (HDB). At present, the synaptic connectivity of the cholinergic axons on the circuits of the OB has only been investigated in the rat. In this report, we analyze the synaptic connectivity of the cholinergic axons in the OB of the cynomolgus monkey (Macaca fascicularis). Our aim is to investigate whether the cholinergic innervation of the bulbar circuits is phylogenetically conserved between macrosmatic and microsmatic mammals. Our results demonstrate that the cholinergic axons form synaptic contacts on interneurons. In the glomerular layer, their main targets are the periglomerular cells, which receive axo-somatic and axo-dendritic synapses. In the inframitral region, their main targets are the granule cells, which receive synaptic contacts on their dendritic shafts and spines. Although the cholinergic boutons were frequently found in close vicinity of the dendrites of principal cells, we have not found synaptic contacts on them. From a comparative perspective, our data indicate that the synaptic connectivity of the cholinergic circuits is highly preserved in the OB of macrosmatic and microsmatic mammals.

No MeSH data available.


Related in: MedlinePlus