Olfaction in Lamprey Pallium Revisited—Dual Projections of Mitral and Tufted Cells

Shreyas M Suryanarayana,Juan Pérez-Fernández,Brita Robertson,Sten Grillner

doi:10.1016/j.celrep.2020.108596

Shreyas M Suryanarayana, Juan Pérez-Fernández + Show 2 more

Open Access

https://doi.org/10.1016/j.celrep.2020.108596

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Journal: Cell Reports	Publication Date: Jan 1, 2021
Citations: 19	License type: cc-by

Affiliation: Karolinska Institutet

Abstract

The presence of two separate afferent channels from the olfactory glomeruli to different targets in the brain is unravelled in the lamprey. The mitral-like cells send axonal projections directly to the piriform cortex in the ventral part of pallium, whereas the smaller tufted-like cells project separately and exclusively to a relay nucleus called the dorsomedial telencephalic nucleus (dmtn). This nucleus, located at the interface between the olfactory bulb and pallium, in turn projects to a circumscribed area in the anteromedial, ventral part of pallium. The tufted-like cells are activated with short latency from the olfactory nerve and terminate with mossy fibers on the dmtn cells, wherein they elicit large unitary excitatory postsynaptic potentials (EPSPs). In all synapses along this tufted-like cell pathway, there is no concurrent inhibition, in contrast to the mitral-like cell pathway. This is similar to recent findings in rodents establishing two separate exclusive projection patterns, suggesting an evolutionarily conserved organization.

Highlights

Olfaction is an important sense for all vertebrates, but is the olfactory system organized in a similar way? In rodents, olfaction is mediated by around a thousand genetically specified receptors for different specific odorants (Buck and Axel, 1991)
Brief pulses of odorants activate the tufted cells with shorter latency and more effectively, as compared to the mitral cells activated with a longer latency and a somewhat higher threshold (Igarashi et al, 2012; Liu et al, 2019; Manabe and Mori, 2013)
We show that stimulation of the olfactory nerve leads to large excitatory postsynaptic potentials (EPSPs) in the dmtn, which in turn projects to a small circumscribed area in the rostral, ventral part of pallium

Summary

Introduction

Olfaction is an important sense for all vertebrates, but is the olfactory system organized in a similar way? In rodents, olfaction is mediated by around a thousand genetically specified receptors for different specific odorants (Buck and Axel, 1991). Brief pulses of odorants activate the tufted cells with shorter latency and more effectively, as compared to the mitral cells activated with a longer latency and a somewhat higher threshold (Igarashi et al, 2012; Liu et al, 2019; Manabe and Mori, 2013). This is true for responses to electrical stimulation of the olfactory afferents (Shepherd, 2004). The mitral cells have, on the other hand, a very broad projection pattern over the entire piriform cortex (Choi et al, 2011; Igarashi et al, 2012)

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