Ординатура / Офтальмология / Английские материалы / Eye, Retina, and Visual System of the Mouse_Chalupa, Williams_2008

Plate 20 The anatomical locations of the medial RALDH3 band are indicated for P15 in the form of a color code, in which prefrontal includes the prelimbic and medial orbital cortices; cingulate includes areas 1 and 2 of the cingulate cortex; motor designates mostly the secondary motor cortex, in addition to a small caudal part of the

primary motor cortex; parietal includes the medial and lateral parietal association cortices; and medial extrastriate extends from a location where the rostral extrastriate region abuts the parietal association cortex all the way caudally, an elongated region also called area 18b or V2M (Wagner et al., 2006). (See figure 30.4.)

RGC cell bodies and axons

Netrin-1/EphA4

EphB2/B3 and BMPR1

CSPG

Slit1

Slit2

Sema5A

Hs2st

Hs6st1 Ephrin-B2–expressing radial glia cells

Plate 21 Cues that guide RGC axons through the visual pathway. Top, RGC axons (blue) express many receptors for a number of cues in the retina that guide them toward the optic disc and out of the retina. Bottom, A variety of cues surrounding the optic nerve,

chiasm, and tract help to funnel RGC axons properly through the ventral diencephalon toward their final targets, the LGN and SC. ODAPs, optic disc astrocyte precursor cells. (See figure 32.2.)

Plate 22 Important techniques for studying RGC projections in the developing mouse visual system. A, DT and VT retinal explants plated near a border of 0.5 μg/mL ephrin-B2 (red). Axons from DT explants project into the ephrin-B2 region, while VT axons are clearly inhibited. B, Time-lapse imaging can be used to study RGC growth cone behavior in real time as they encounter a border, in this case ephrin-B2. Arrowheads highlight two growth cones, one of which projects into the ephrin-B2 region and the other of which is repelled and travels parallel to the ephrin-B2 border. C, Diagram

depicting in utero retinal electroporation. Briefly, DNA is injected into embryonic retina. Current is passed through electroporation paddles, and embryos are allowed to survive for several days. Embryos are perfused, the retina is collected, and heads are cryosectioned. In this case, GFP-positive cells can be seen in the retina, and many GFP-positive RGC projections are visible through the optic nerve, chiasm, and tract. Red denotes neurofilament. (See figure 32.5.) (All images courtesy of T. Petros and C. Mason.)

Plate 23 After an optic nerve crush injury, RGC axons were labeled with an intravitreal injection of fluorophore-conjugated cholera toxin B. The bright axons (green) failed to regrow across

the lesion site (arrows) after 8 days in vivo. Optic nerve nuclei are counterstained with a nuclear dye, DAPI. (See figure 33.6.) (Y. Duan and J. L. Goldberg. [2008]. Unpublished data.)

A

contra ipsi superimposed

Plate 24 Retinogeniculate axon segregation in the developing mouse. A, Anterograde transport of CTβ conjugated to Alexa Fluor 594 (red) labels contralateral eye projections, and anterograde transport of CTβ conjugated to Alexa Fluor 488 (green) labels ipsilateral eye projections. Panels from left to right depict red and green fluorescence labeling of the same section of LGN. Adjacent to these are the superimposed fluorescent pattern and corresponding pseudo-colored image, where pixel intensity is assigned a single value above a defined threshold. Pixels that contain both red and green fluorescence are considered areas of overlap and are represented in yellow. Scale bar = 100 μm. B, Pixel intensity analysis reveals degree of eye-specific segregation in the developing LGN. Top, Scatterplots of pixel intensity for a single section through LGN at P3 and P28. Each point represents a pixel in which the fluorescence intensity of the ipsilateral projection is plotted against the intensity of the contralateral projection. At P3, when projections overlap, pixel intensities show a positive correlation. At P28, pro-

jections are segregated and pixel intensities show a negative correlation. Bottom, Corresponding R distributions of pixel intensity. For each pixel the logarithm of the intensity ratio (R = log10 FI/FC) is plotted as a frequency histogram (bin size = 0.1 log units). A narrow R distribution (P3) shows an unsegregated pattern; a wide one (P28) shows a segregated pattern. C, Summary plots showing the spatial extent of retinal projections (left) and the variance of R distributions (right) at different ages. Left, Percent area in LGN occupied by contralateral, ipsilateral, and overlapping terminal fields at different ages. Each point represents the mean and SEM for a group of same-aged animals. Note that ipsilateral projections and the degree of overlap recede between P3 and P12. Right, Mean and SEM variance values obtained from R distributions. Changes in spatial extent are accompanied by a parallel increase in variance and reflect a progressive increase in the degree of eye-specific segregation between P3 and P12. (See figure 34.2.) (Adapted from JaubertMiazza et al., 2005.)

Plate 25 Retinotopic mapping of mouse binocular visual cortex using optical imaging of intrinsic signals. A, Schematic illustration of primary visual pathway in the mouse, depicting the location of the dorsal lateral geniculate nucleus (dLGN) and the primary visual cortex (V1), with the binocular zone (bV1) located laterally. B, Top, Cortical blood vessel pattern as imaged through the skull. Bottom, Arrangement of grating stimuli used to map the central visual field. Color denotes stimulus position. C, Individual activity maps dis-

playing responses to the 3 × 3 stimulus grid depicted in B are presented separately to the two eyes. The coordinates of the yellow cross are fixed in each map. D and E, Color-coded maps of the combined responses to contralateral (D) and ipsilateral (E) eye stimulation superimposed on the cortical blood vessel pattern, revealing the extent of the binocular zone. Color indicates stimulus position eliciting the strongest response at each pixel. Scale bars = 0.5 mm. (See figure 36.1.)

Plate 26 Mapping OD in mouse binocular visual cortex by twophoton calcium imaging. A, Examples of visually evoked calcium transients (fluorescent change, F/F) recorded from two different neurons in the binocular visual cortex loaded with the calcium indicator dye OGB-1AM. Thin traces show individual responses to stimulation of each eye; thick traces are average responses to eight stimulus presentations. Stimulation periods are indicated by gray bars. B, Response maps ( F) for the contralateral (left panel ) and ipsilateral (right panel ) eye 230 μm below the pial surface in a normal mouse. C, A cell-based OD map computed from the single-eye

response maps in B. Individual neurons are color coded by the OD score, as indicated by the labels in D. OD score of 1 or 0 denotes exclusive response to contralateral or ipsilateral eye stimulation, respectively, and a value of 0.5 indicates an equal response to both eyes. D, Overlay of cell-based OD maps at different depths for a normal mouse (left, four depths, 190–290 μm), after a 5-day contralateral MD (center, six depths, 195–410 μm), and after a 5-day ipsilateral MD (right, two depths, 200 and 225 μm). Note weak clustering of cells with similar OD values in the normal mouse. Scale bars = 50 μm. (See figure 36.3.)

C

Contra/ipsi-ratio

1.4

1.2

1.0

0.8

0.6

Plate 27 OD plasticity in adult visual cortex assessed with intrinsic signal imaging and multielectrode recordings. A and B, Ipsilateral and contralateral eye responses in the same mouse before (A, P80, contralateral/ipsilateral ratio = 2.21) and after 6 days of MD (B, P92, contralateral/ipsilateral ratio = 1.09). Stimulus arrangement as in figure 36.2A. C, Ratio of contralateral to ipsilateral eye response strength after 6–7 days of MD in normal adult mice plotted against age shows no significant correlation. R2 = 0.12, P = 0.24. D, Contralateral/ipsilateral ratio values from repeated experiments in adult control animals (gray, interimaging period

1–3 weeks) and in deprived adult animals before and after 6 days of MD in the contralateral eye (black). E, Functional map of the binocular region (green corresponds to the ipsilateral eye representation), used for targeting electrode penetrations (circles). Scale bar = 0.5 mm. F, Distribution of contralateral/ipsilateral ratio values from all recording sites in adult control (2.99 ± 0.28, mean

± SEM, 324 recording sites, 4 mice) and deprived (1.05 ± 0.12, 260 recording sites, 5 mice) animals, showing strong OD shifts in response to MD. Each color represents a different animal. Horizontal lines indicate mean group values. (See figure 36.4.)

B

Non-EE

P10 P20 P25 P30

19-20 22-23 25-26 28-29 34-35 44-45

Plate 28 Acceleration of visual system development by environmental enrichment. A, EE accelerates the maturation of visual acuity. Visual acuity of non-EE (green) and EE (red) rats has been assessed by means of visual evoked potentials (VEPs) recorded from the binocular portion of the visual cortex at different ages during postnatal development. VEP acuity is normalized to the acuity value at P44–P45 and is plotted as a function of age for each experimental group to show the leftward shift of the curve for EE animals. B, Higher levels of BDNF and GAD65/67 expression in EE pups. ELISA and Western blot analysis have been used to measure, respectively, BDNF and GAD65/67 protein levels in the visual cortex of EE and non-EE animals at different postnatal ages. Data are plotted as percentage of variation between the two groups,

with positive values indicating higher levels in EE mice. C, Accelerated CRE-mediated gene expression development in the visual cortex of EE mice. C1, Examples of brains at different ages (P10–P30) from CRE-lacZ transgenic mice reared in non-EE or EE conditions. X-gal histochemistry has been used to reveal the occurrence of CRE-mediated gene expression (blue precipitate). C2, Quantification of the density of X-gal-positive cells for non-EE (green) and EE (red) mice at the indicated ages. Fields were chosen to sample layers II–VI of the binocular visual cortex. CREmediated gene expression is developmentally regulated in both groups, but its peak is accelerated in EE mice. (See figure 37.1.) (A, Modified from Landi et al., 2007b. B and C, Modified from Cancedda et al., 2004.)

B

Cell percentage

DR-EE+MD

100

DR-non-EE+MD

MD adult

normal

80

60

40

20

0

CBI

0,3

0,2

0,1

0

Plate 29 Environmental enrichment promotes consolidation of visual cortical connections in dark-reared rats. A, Schematic diagram of the dark-rearing (DR) protocol combined with EE. Newborn rats were reared in complete darkness from P0 until P50. Together with DR, they were maintained, starting from P18, in either non-EE or EE conditions. Rats were then subjected to 1 week of MD, in normal light conditions. B and C, Normal closure of the critical period for MD in EE rats. B, Summary of MD effects in all DR animals. The OD distribution of each animal has been summarized with the contralateral bias index (CBI = {[N(1) − N(7)] + 1/2[N(2/3) − N(5/6)] + N(Tot)}/2N(Tot), where N(tot) is the total number of recorded cells and N(i) is the number of cells in class (i) (open diamonds denote individual data; circles denote mean of the group ± SE). CBI scores in DR-non-EE + MD rats differ from those in DR-EE + MD rats, which do not differ from those in

normal adults (shaded rectangle). C, Cumulative fractions for OD scores. For each cell, an OD score was computed as {[Peak(ipsi) − baseline(ipsi)] − [Peak(contra) − baseline(contra)]}/{[Peak(ipsi) − baseline(ipsi)] + [Peak(contra) − baseline(contra)]} (Rittenhouse et al., 1999). This score is −1 for class 1 cells, +1 for class 7 cells, and around 0 for class 4 cells. Only the curve for DR + non-EE MD animals significantly differs from that in normal rats. D, Examples of staining for Wisteria floribunda agglutinin (which labels perineural nets, green) and NeuN (neuronal marker, red) in Oc1B of a normal rat, a DR-non-EE rat, and a DR-EE rat at P50. The decrease caused by DR in the number of perineural net– surrounded neurons is reduced in EE-DR animals. Calibration bar = 100 μm. (See figure 37.2.) (Modified from Bartoletti et al., 2004.)

I) Prenatal maternal influence (embryonic life)

Placental exchanges

Possible factors: IGF-I

Observed changes: increased IGF-I levels in the RGC layer Accelerated dynamics of natural RGCs’ death

Plate 30 Model of environmental enrichment effects on visual system development and plasticity. Shown is an interpretive framework for understanding the data on EE influence on the developing visual system. The effects elicited by EE on visual system development and plasticity are due not only to changes in the levels of sensory visual stimulation but also to very early factors activated even in the absence of vision. The available data support a model in which three distinct temporal phases during pup development are differently controlled by the richness of the environment: a

prenatal phase in which the mother mediates the influence of the environment through placental exchanges with the fetus, an early postnatal phase in which higher levels of maternal care in EE stimulate the expression of experience-dependent factors in the visual system, and a third (and final) phase in which the autonomous interaction of the developing pup with the enriched environment further promotes the maturation of visual functions (see the text for details). (See figure 37.5.)

Plate 31 The extended duration VEP recording technique is a reliable method to assess OD plasticity in mice. A, Representation of VEP recording setup. A mouse previously implanted with recording electrodes in Oc1 is placed in a restraint apparatus in front of a computer monitor displaying visual stimuli. Mice are fully awake and alert during all recording sessions. B, Schematic diagram of the mouse visual system. Input from the stronger contralateral eye arrives via the LGN to the monocular and binocular zones of V1, whereas input from the weaker ipsilateral eye projects only to the small binocular zone. C, Current source density profile of VEPs for an adult mouse. Binocular VEP depth profile is shown in the left panel, with the corresponding cortical layers designated by arrowheads. Middle panel shows the CSD profile. Current sinks are nega-

tive-going and shaded black. The color image plot in the right panel is an interpolation of CSD traces. The earliest latency current sink is observed in layer 4, followed by longer latency sinks in layers 2/3 and 5. Cold and warm colors represent current sinks and sources, respectively. D, Typical VEP responses obtained during the three viewing conditions used in all experiments. Each trace is an average of 100 presentations of a reversing (1 Hz) sinusoidal grating. E, VEPs recorded from awake mice are stable over several days. Displayed in the left panel are the average VEP amplitude (n = 6 mice) in response to contralateral eye (blue bars) and ipsilateral eye (yellow bars) stimulation at baseline (day 0) and after 5 days of normal visual experience. Right panel shows the stability of contralateral/ ipsilateral ratios over days. (See figure 38.1.)