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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.


Synaptic connectivity of the cholinergic circuits in the macaque olfactory bulb. Cholinergic axons establish synaptic contacts on bulbar interneurons. On the one hand, cholinergic fibers form synaptic contacts on the somata, dendrites and dendritic appendages of type 1 (TH-containing) and type 2 (CR-containing) periglomerular cells. In addition, cholinergic axons form synaptic contacts on the dendrites and appendages of granule cells (Gr). We cannot discard sporadic synapses (?) from cholinergic axons on superficial short-axon cells (SSA). Synaptic contacts from cholinergic axons on mitral (M) and tufted (ET) cells were never found. Abbreviations: CR: type 2, calretinin-containing periglomerular cells (orange); EPL: external plexiform layer; ET: tufted cell (dark green); GCL: granule cell layer; GL: glomerular layer; Gr: granule cells (purple); M: Mitral cell (green); MCL: mitral cell layer; ON: olfactory nerve (blue). ONL: olfactory nerve layer. SSA: superficial-short-axon cell (pink); TH: type 1, tyrosine hydroxylase-containing periglomerular cells (brown).
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Figure 10: Synaptic connectivity of the cholinergic circuits in the macaque olfactory bulb. Cholinergic axons establish synaptic contacts on bulbar interneurons. On the one hand, cholinergic fibers form synaptic contacts on the somata, dendrites and dendritic appendages of type 1 (TH-containing) and type 2 (CR-containing) periglomerular cells. In addition, cholinergic axons form synaptic contacts on the dendrites and appendages of granule cells (Gr). We cannot discard sporadic synapses (?) from cholinergic axons on superficial short-axon cells (SSA). Synaptic contacts from cholinergic axons on mitral (M) and tufted (ET) cells were never found. Abbreviations: CR: type 2, calretinin-containing periglomerular cells (orange); EPL: external plexiform layer; ET: tufted cell (dark green); GCL: granule cell layer; GL: glomerular layer; Gr: granule cells (purple); M: Mitral cell (green); MCL: mitral cell layer; ON: olfactory nerve (blue). ONL: olfactory nerve layer. SSA: superficial-short-axon cell (pink); TH: type 1, tyrosine hydroxylase-containing periglomerular cells (brown).

Mentions: The results shown here constitute the first report of the synaptic connectivity of the cholinergic system in the OB of primates (Figure 10). Our data demonstrate that the cholinergic axons found in the macaque OB form axo-somatic and axo-dendritic synaptic contacts on bulbar interneurons, mainly on periglomerular cells and granule cells. Although we have found VAChT-containing axons in juxtaposition with the dendrites of mitral and tufted cells, cholinergic synapses were never found on principal cells. Our data are in close agreement with those previously reported in rodents, and demonstrate that the synaptic action of the cholinergic system on the bulbar circuitry remains largely preserved between macrosmatic and microsmatic mammals.


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)

Synaptic connectivity of the cholinergic circuits in the macaque olfactory bulb. Cholinergic axons establish synaptic contacts on bulbar interneurons. On the one hand, cholinergic fibers form synaptic contacts on the somata, dendrites and dendritic appendages of type 1 (TH-containing) and type 2 (CR-containing) periglomerular cells. In addition, cholinergic axons form synaptic contacts on the dendrites and appendages of granule cells (Gr). We cannot discard sporadic synapses (?) from cholinergic axons on superficial short-axon cells (SSA). Synaptic contacts from cholinergic axons on mitral (M) and tufted (ET) cells were never found. Abbreviations: CR: type 2, calretinin-containing periglomerular cells (orange); EPL: external plexiform layer; ET: tufted cell (dark green); GCL: granule cell layer; GL: glomerular layer; Gr: granule cells (purple); M: Mitral cell (green); MCL: mitral cell layer; ON: olfactory nerve (blue). ONL: olfactory nerve layer. SSA: superficial-short-axon cell (pink); TH: type 1, tyrosine hydroxylase-containing periglomerular cells (brown).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 10: Synaptic connectivity of the cholinergic circuits in the macaque olfactory bulb. Cholinergic axons establish synaptic contacts on bulbar interneurons. On the one hand, cholinergic fibers form synaptic contacts on the somata, dendrites and dendritic appendages of type 1 (TH-containing) and type 2 (CR-containing) periglomerular cells. In addition, cholinergic axons form synaptic contacts on the dendrites and appendages of granule cells (Gr). We cannot discard sporadic synapses (?) from cholinergic axons on superficial short-axon cells (SSA). Synaptic contacts from cholinergic axons on mitral (M) and tufted (ET) cells were never found. Abbreviations: CR: type 2, calretinin-containing periglomerular cells (orange); EPL: external plexiform layer; ET: tufted cell (dark green); GCL: granule cell layer; GL: glomerular layer; Gr: granule cells (purple); M: Mitral cell (green); MCL: mitral cell layer; ON: olfactory nerve (blue). ONL: olfactory nerve layer. SSA: superficial-short-axon cell (pink); TH: type 1, tyrosine hydroxylase-containing periglomerular cells (brown).
Mentions: The results shown here constitute the first report of the synaptic connectivity of the cholinergic system in the OB of primates (Figure 10). Our data demonstrate that the cholinergic axons found in the macaque OB form axo-somatic and axo-dendritic synaptic contacts on bulbar interneurons, mainly on periglomerular cells and granule cells. Although we have found VAChT-containing axons in juxtaposition with the dendrites of mitral and tufted cells, cholinergic synapses were never found on principal cells. Our data are in close agreement with those previously reported in rodents, and demonstrate that the synaptic action of the cholinergic system on the bulbar circuitry remains largely preserved between macrosmatic and microsmatic mammals.

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.