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Liberia T, Blasco-Ibáñez JM, Nácher J, Varea E, Lanciego JL, Crespo C. Synaptic connectivity of the cholinergic axons in the olfactory bulb of the cynomolgus monkey. Front Neuroanat. 2015 Mar 17;9:28
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.