Organization of myelin in the mouse somatosensory barrel cortex and the effects of sensory deprivation - PubMed (original) (raw)
Organization of myelin in the mouse somatosensory barrel cortex and the effects of sensory deprivation
Kyrstle Barrera et al. Dev Neurobiol. 2013 Apr.
Abstract
In rodents, the barrel cortex is a specialized area within the somatosensory cortex that processes signals from the mystacial whiskers. We investigated the normal development of myelination in the barrel cortex of mice, as well as the effects of sensory deprivation on this pattern. Deprivation was achieved by trimming the whiskers on one side of the face every other day from birth. In control mice, myelin was not present until postnatal day 14 and did not show prominence until postnatal day 30; adult levels of myelination were reached by the end of the second postnatal month. Unbiased stereology was used to estimate axon density in the interbarrel septal region and barrel walls as well as the barrel centers. Myelin was significantly more concentrated in the interbarrel septa/barrel walls than in the barrel centers in both control and sensory-deprived conditions. Sensory deprivation did not impact the onset of myelination but resulted in a significant decrease in myelinated axons in the barrel region and decreased the amount of myelin ensheathing each axon. Visualization of the oligodendrocyte nuclear marker Olig2 revealed a similar pattern of myelin as seen using histochemistry, but with no significant changes in Olig2+ nuclei following sensory deprivation. Consistent with the anatomical results showing less myelination, local field potentials revealed slower rise times following trimming. Our results suggest that myelination develops relatively late and can be influenced by sensory experience.
Copyright © 2012 Wiley Periodicals, Inc.
Figures
Figure 1
P60 control tissue stained for myelin. Coronal section reveals myelinated axons in the barrel cortex running perpendicular to the pial surface terminating by layer IV (A). Low-magnification images reveal the barrel pattern (B), whereas higher magnifications (C and D) highlight individual myelinated axons cut in cross section in the tangential plane. Note that myelinated axons are sparser within the barrel hollows than in the septa/wall regions.
Figure 2
Quantifying myelin. A P60 AuCl-stained tangential section (A) with barrel wall and barrel hollow contours indicated. High magnification (B) displays the difference in axon density between barrel wall and hollow (B) and how the quick measure line tool was used to quantify axon diameter. A schematic of the contours and counting frames that were utilized for stereological analyses is depicted (C). The counting frame (red and green box) is placed by the software program (Stereo Investigator) in the top left corner of the grid (blue lines), myelinated axons that cross the green line are counted those that intersect the red line are not to prevent double counting. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com
.]
Figure 3
Density of myelinated axons increases significantly during development. Control tissue stained for myelin at P14 (A), P21 (B), P30 (C), P45 (D), P60 (E), and P90 (F). Myelination increases over normal development in both the barrel hollow and septal/barrel wall regions. Quantification of myelinated axonal density (G) reveals a significant increase between P45 and P60 in the barrel [F(5,26) = 22.304, p < 0.001] and in the septa [F(5,26) = 28.616, p < 0.001]. Data points represent population means and one standard error of the mean.
Figure 4
Myelin basic protein staining in the mouse barrel cortex. Tangential sections at P32 tangential sections at low (A) and high magnifications (C) reveal a barrel pattern as do images from P62 animals at low (B) and high magnifications (D). Quantification of myelin basic protein + axons in the barrel hollow and barrel wall shows that barrel walls have greater densities of transected myelinated axons than barrel hollows at both time points (E and F).
Figure 5
Gold chloride labeling and myelin basic protein labeling are equivalent in the mouse barrel cortex. P30 and P60 tangential sections using AuCl labeling (A and C) revealed similar patterns of staining when compared P32 and P62 tangential sections labeled with an antibody to myelin basic protein (B and D). The ratio of barrel hollow to barrel wall is consistent between AuCl (E) and myelin basic protein labeling (F).
Figure 6
Diameter of myelinated axons increases significantly during development. Myelin diameter significantly increased over development in both the barrel hollow and barrel wall/septal regions peaking at P45–P60 before returning to mature levels at P90 [F(13,766) = 14.685, p < 0.001; F(13,766) = 18.778, p < 0.001, respectively]. The data represent population means and one standard error of the mean.
Figure 7
Whisker trimming decreases density of myelinated axons in the barrel and septal/barrel wall regions. Control (A) and deprived (B) tissue at P60 stained for myelin. Myelination is significantly reduced in the barrel hollow region of the sensory-deprived animals in the P30-P60 trim group and in the Trim30/Regrow30 group [F(13,64) = 36.369, p < 0.001] (C). Myelination is significantly reduced in the septal/barrel wall region of sensory-deprived animals at P60, and in the P30-P60 trim group, Trim30/Regrow30 group, and an increase in the P90-P120 trim group [F(13,64) = 51.015, p < 0.001] (D). Bars represent population means and one standard error of the mean. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com
.]
Figure 8
Whisker trimming decreases the diameter of transected myelinated axons. Whisker trimming decreased the diameter of transected myelinated axons in the barrel hollow (A) at P60 [F(14,765) = 13.693, p < 0.001] and in the septa/barrel wall (B) at P45 and P60 [F(13,766) = 18.778, p < 0.001]. Bars represent population means and one standard error of the mean.
Figure 9
Cell density and oligodendrocyte density were not affected by sensory deprivation. Representative nissl-stained tangential section from P60 control animal at low magnification (A) shows the barrel field and Olig2+ oligodendrocytes. White arrows indicate nissl-stained cells, and black arrows indicate cells double stained for both Olig2+ and nissl. Overall cell numbers and oligodendrocyte density were unaffected by sensory deprivation (C and D). Bars represent population means and one standard error of the mean. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com
.]
Figure 10
Local field potential recordings from barrel cortex. Tungsten microelectrodes were manually inserted into layer IV (dotted lines, A). Local field potentials reveal that responses from the intact side (control, red trace) had a faster rate of rise than those on the deprived side (trim, blue trace). Black trace indicates onset and offset of the air puff, and field potentials are averaged in response to 100 stimulus presentations. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com
.]
References
- Allen CB, Celikel T, Feldmen DE. Long-term depression induced by sensory deprivation during cortical map plasticity in vivo. Nat Neurosci. 2003;6:291–299. -PubMed
- Brumberg JC, Pinto DJ, Simons DJ. Cortical columnar processing in the rat whisker-to-barrel system. J Neurophysiol. 1999;82:1808–1817. -PubMed
- Clopton BM, Silverman MS. Changes in latency and duration of neural responding following developmental auditory deprivation. Exp Brain Res. 1978;32:39–47. -PubMed
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