Morphometric analysis of feedforward pathways from the primary somatosensory area (S1) of rats
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Abstract
In this report, we used biotinylated dextran amine to anterogradely label individual axons projecting from primary somatosensory cortex (S1) to four cortical areas in rats, namely the secondary somatosensory (S2), the parietal ventral (PV), the perirhinal (PR), and the contralateral S1 (S1c). A major goal was to determine whether axon terminals could be classified on the basis of morphological criteria, such as the shape and density of boutons, and the shape and size of individual terminal arbors. Evidence from reconstruction of isolated axon terminal fragments (n=111) supported a degree of morphological heterogeneity. In particular, morphological parameters associated with the complexity of terminal arbors and the proportion of beaded, en passant boutons (Bp) vs. stalked boutons terminaux (Bt) were found to differ significantly. Two broad groups could be established following a discriminant function analysis across axon fragments. Both groups occurred in all four target areas, possibly consistent with a commonality of presynaptic processing of tactile information in these areas. However, more work is needed to investigate synaptic function at the single bouton level and see how this might be associated with emerging properties in the postsynaptic targets.
Cite this as
2014. Morphometric analysis of feedforward pathways from the primary somatosensory area (S1) of rats. PeerJ PrePrints 2:e480v2 https://doi.org/10.7287/peerj.preprints.480v2Author comment
This is version 2 of the manuscript. We fixed some small errors: Labels of Figures 3 and 4 were switched and we removed the word "tangentially" from the Material and Methods section.
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Supplemental Information
Morphometric Data
Morphometric data for axon terminals. Each sheet is related to a target area (S2, PV, PR, S1c). The variables are declared on column titles, axon terminal ID, number of branching points, number of synaptic boutons, number of segments, total length of segments in mm, number of bouton terminaux (Bt), number of bouton en passant (Bp)
Additional Information
Competing Interests
There are no competing interests.
Author Contributions
Andrea Lima de Sá performed the experiments, analyzed the data, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Vânia Castro Corrêa performed the experiments, analyzed the data, reviewed drafts of the paper.
Carlomagno Pacheco Bahia conceived and designed the experiments, analyzed the data, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Ivanira Dias performed the experiments, reviewed drafts of the paper.
Walace Gomes Leal analyzed the data, contributed reagents/materials/analysis tools, reviewed drafts of the paper.
André Luís Santos Pinho analyzed the data, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Jean-Christophe Houzel conceived and designed the experiments, analyzed the data, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Cristovam Wanderley Picanço Diniz analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, reviewed drafts of the paper.
Antonio Pereira conceived and designed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, reviewed drafts of the paper.
Animal Ethics
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
Experimental procedures were approved by the Federal University of Pará Ethics Committee for the Use of Animals (BIO015-09).
Funding
This work was supported by grants from CNPq (476627/2011-7) and CNPq (483404/2013-6). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
