The topography of rods, cones and intrinsically photosensitive retinal ganglion cells in the retinas of a nocturnal (Micaelamys namaquensis) and a diurnal (Rhabdomys pumilio) rodent

Reconfiguration of the visual code and retinal cell type complement in closely related diurnal and nocturnal mice

How does evolution act on neuronal populations to match computational characteristics to functional demands? We address this problem by comparing visual code and retinal cell composition in closely related murid species with different behaviours. Rhabdomys pumilio are diurnal and have substantially thicker inner retina and larger visual thalamus than nocturnal Mus musculus. High-density electrophysiological recordings of visual response features in the dorsal lateral geniculate nucleus (dLGN) reveals that Rhabdomys attains higher spatiotemporal acuity both by denser coverage of the visual scene and a selective expansion of elements of the code characterised by non-linear spatiotemporal summation. Comparative analysis of single cell transcriptomic cell atlases reveals that realignment of the visual code is associated with increased relative abundance of bipolar and ganglion cell types supporting OFF and ON-OFF responses. These findings demonstrate how changes in retinal cell complement can reconfigure the coding of visual information to match changes in visual needs.

Comparative light and scanning electron microscopic studies of the lenses in the insectivorous bat (Pipistrellus kuhlii) and Egyptian fruit bat (Rousettus aegyptiacus)

Bats have the ability to fly without eye application in the darkness. In this study, we aimed to characterize the functional and structural acclimations of the lenses of two common bats with a various lifestyle in the Egyptian environment: the insectivorous bat (IB) (Pipistrellus kuhlii) and Egyptian fruit bat (FB) (Rousettus aegyptiacus). From each species, seven lenses were extracted from adult eyes. The scanning electron microscopic (SEM) and light microscopic examination of the lens were carried out. FB lenses were made up primarily of fiber cells and sheets, which were encapsulated by a thin collagenous capsule and covered by single epithelial layer anteriorly. On the other hand, the IB lens had two poles and was visibly oval shaped. Both lenses had epithelial cells of the same cuboidal form that were subjected to continuous division and differentiation into new fiber cells at the center. SEM revealed that the normal FB lens had regularly organized shells of fiber cells of intact lens fibers which were connected by membrane interdigitations with different shapes mainly ball-and-socket junctions through the superficial cortical fiber cells. The IB lens was composed of parallel, evenly spaced fibers with various types of interdigitations between fibers that can be seen and increased close to the middle region revealing tiny bumps along the scrubby portions and sockets and balls in the center of the wide portions. Near the center of both lenses, there were large interlocking paddles with little and lengthy protrusions along their short sides. In conclusion, our study discovered several ultrastructural and structural variations among the investigated species. The detection of specialized membrane interdigitations with different shapes protruding from the lens fiber sheets is considered the most characteristic of the FB lens. RESEARCH HIGHLIGHTS: FB lens has more organized sheets of fibers parallel to each other than IB lens. Different shapes of interdigitations protruded from the FB lens have been detected. Interlocking paddles, balls, and sockets with tongue-like fiber flabs are characteristic to FB lens.

Wild mice in an urbanized world: Effects of light at night under natural and laboratory conditions in the single-striped grass mouse (Lemniscomys rosalia)

Urbanization, and the accompanying artificial light at night (ALAN), can disrupt the activity of animals. Such disruptions at the base of a food web can ripple through the ecosystem. Most studies of ALAN are performed in the laboratory. Thus, we lack basic information about the circadian responses of animals under natural environmental conditions to fully evaluate the impact of ALAN. We studied the behaviour and activity of wild-caught, peri-urban single-striped grass mice (Lemniscomys rosalia) under a natural treatment and in a standard laboratory treatment, including dim light at night to mimic conditions that they could experience. The species exhibited predominantly crepuscular activity under all experimental treatments. It showed the highest level of activity under the natural treatment, whereas ALAN significantly suppressed its activity. Males were more active than females under all experimental treatments. The marked changes in activity under ALAN is of particular concern since global change in combination with urbanization can lead to a change in vegetation density and composition that will decrease the number of suitable microhabitats and expose small mammals to novel habitat changes. We suggest that the single-striped mice could become vulnerable because of urbanization, leading to impacts on its ecosystem broadly.

The genomic basis of temporal niche evolution in a diurnal rodent

Patterns of diel activity-how animals allocate their activity throughout the 24-h daily cycle-play key roles in shaping the internal physiology of an animal and its relationship with the external environment.1,2,3,4,5 Although shifts in diel activity patterns have occurred numerous times over the course of vertebrate evolution,6 the genomic correlates of such transitions remain unknown. Here, we use the African striped mouse (Rhabdomys pumilio), a species that transitioned from the ancestrally nocturnal diel niche of its close relatives to a diurnal one,7,8,9,10,11 to define patterns of naturally occurring molecular variation in diel niche traits. First, to facilitate genomic analyses, we generate a chromosome-level genome assembly of the striped mouse. Next, using transcriptomics, we show that the switch to daytime activity in this species is associated with a realignment of daily rhythms in peripheral tissues with respect to the light:dark cycle and the central circadian clock. To uncover selection pressures associated with this temporal niche shift, we perform comparative genomic analyses with closely related rodent species and find evidence of relaxation of purifying selection on striped mouse genes in the rod phototransduction pathway. In agreement with this, electroretinogram measurements demonstrate that striped mice have functional differences in dim-light visual responses compared with nocturnal rodents. Taken together, our results show that striped mice have undergone a drastic change in circadian organization and provide evidence that the visual system has been a major target of selection as this species transitioned to a novel temporal niche.

Evolution of neuronal cell classes and types in the vertebrate retina

The basic plan of the retina is conserved across vertebrates, yet species differ profoundly in their visual needs (Baden et al., 2020). One might expect that retinal cell types evolved to accommodate these varied needs, but this has not been systematically studied. Here, we generated and integrated single-cell transcriptomic atlases of the retina from 17 species: humans, two non-human primates, four rodents, three ungulates, opossum, ferret, tree shrew, a teleost fish, a bird, a reptile and a lamprey. Molecular conservation of the six retinal cell classes (photoreceptors, horizontal cells, bipolar cells, amacrine cells, retinal ganglion cells [RGCs] and Muller glia) is striking, with transcriptomic differences across species correlated with evolutionary distance. Major subclasses are also conserved, whereas variation among types within classes or subclasses is more pronounced. However, an integrative analysis revealed that numerous types are shared across species based on conserved gene expression programs that likely trace back to the common ancestor of jawed vertebrates. The degree of variation among types increases from the outer retina (photoreceptors) to the inner retina (RGCs), suggesting that evolution acts preferentially to shape the retinal output. Finally, we identified mammalian orthologs of midget RGCs, which comprise >80% of RGCs in the human retina, subserve high-acuity vision, and were believed to be primate-specific (Berson, 2008); in contrast, the mouse orthologs comprise <2% of mouse RGCs. Projections both primate and mouse orthologous types are overrepresented in the thalamus, which supplies the primary visual cortex. We suggest that midget RGCs are not primate innovations, but descendants of evolutionarily ancient types that decreased in size and increased in number as primates evolved, thereby facilitating high visual acuity and increased cortical processing of visual information.

Anatomy and Histology of the Eye of the Nutria Myocastor coypus: Evidence of Adaptation to a Semi-aquatic Life

The nutria is a large, semi-aquatic rodent that, being invasive, is having a growing impact on the ecosystem in western Japan. Knowledge regarding physical adaptations to the nutria's lifestyle and habitual activities would be useful for effectively controlling and preventing their spread. Nutrias spend time on land and in water, feeding on agricultural crops and wild grasses growing near the waterside, as well as aquatic plants and shellfish. In the current study, the nutria's visual organ was analyzed anatomically and histologically, and aquatic and light environmental adaptations were evaluated. The results revealed that the nutria eyeball was almost spherical, and the cornea was rounded. The lens was convex and slightly thicker than previously reported for other rodents. These features were not characteristic of aquatic adaptations observed in the eyes of fish or marine mammals. The ratio of lens diameter to eyeball diameter was 0.6, similar to that of nocturnal species. The pupil was a vertical slit, suggesting an ability to adjust the amount of light entering the eyeball during twilight. Photoreceptors were sparsely distributed across the whole retina, and no fovea was observed. Retinal thickness was 90-100 μm, thinner than that in other rodent species. Visual acuity was 1.44-1.58 cycles/degree, higher than that in other rodents, likely because of the nutria's large eyeball and body. These results suggest that the nutria visual system is adapted to recognize large shadows of distant predators rather than viewing objects in detail.

Multinucleated Retinal Pigment Epithelial Cells Adapt to Vision and Exhibit Increased DNA Damage Response

Multinucleated retinal pigment epithelium (RPE) cells have been reported in humans and other mammals. Rodents have an extremely high percentage of multinucleated cells (more than 80%). Both mouse and human multinucleated RPE cells exhibit specific regional distributions that are potentially correlated with photoreceptor density. However, detailed investigations of multinucleated RPE in different species and their behavior after DNA damage are missing. Here, we compared the composition of multinucleated RPE cells in nocturnal and diurnal animals that possess distinct rod and cone proportions. We further investigated the reactive oxygen species (ROS) production and DNA damage response in mouse mononucleated and multinucleated RPE cells and determined the effect of p53 dosage on the DNA damage response in these cells. Our results revealed an unrealized association between multinucleated RPE cells and nocturnal vision. In addition, we found multinucleated RPE cells exhibited increased ROS production and DNA damage after X-ray irradiation. Furthermore, haploinsufficiency of p53 led to increased DNA damage frequency after irradiation, and mononucleated RPE cells were more sensitive to a change in p53 dosage. In conclusion, this study provides novel information on in vivo PRE topography and the DNA damage response, which may reflect specific requirements for vision adaption and macular function.

Clocks Ticking in the Dark: A Review of Biological Rhythms in Subterranean African Mole-Rats

Biological rhythms are rhythmic fluctuations of biological functions that occur in almost all organisms and on several time scales. These rhythms are generated endogenously and entail the coordination of physiological and behavioural processes to predictable, external environmental rhythms. The light-dark cycle is usually the most prominent environmental cue to which animals synchronise their rhythms. Biological rhythms are believed to provide an adaptive advantage to organisms. In the present review, we will examine the occurrence of circadian and seasonal rhythms in African mole-rats (family Bathyergidae). African mole-rats are strictly subterranean, they very rarely emerge aboveground and therefore, do not have regular access to environmental light. A key adaptation to their specialised habitat is a reduction in the visual system. Mole-rats exhibit both daily and seasonal rhythmicity in a range of behaviours and physiological variables, albeit to different degrees and with large variability. We review previous research on the entire circadian system of African mole-rats and discuss output rhythms in detail. Laboratory experiments imply that light remains the strongest zeitgeber for entrainment but in the absence of light, animals can entrain to ambient temperature rhythms. Field studies report that rhythmic daily and seasonal behaviour is displayed in their natural habitat. We suggest that ambient temperature and rainfall play an important role in the timing of rhythmic behaviour in mole-rats, and that they likely respond directly to these zeitgebers in the field rather than exhibit robust endogenous rhythms. In the light of climate change, these subterranean animals are buffered from the direct and immediate effects of changes in temperature and rainfall, partly because they do not have robust circadian rhythms, however, on a longer term they are vulnerable to changes in their food sources and dispersal abilities.

The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species

Since the earliest development of the eye (and vision) around 530 million years ago (Mya), it has evolved, adapting to different habitats, species, and changing environmental conditions on Earth. We argue that a radiation environment determined by the atmosphere played a determining role in the evolution of vision, specifically on the human eye, which has three vision regimes (photopic-, scotopic-, and mesopic vision) for different illumination conditions. An analysis of the irradiance spectra, reaching the shallow ocean depths, revealed that the available radiation could have determined the bandwidth of the precursor to vision systems, including human vision. We used the radiative transfer model to test the existing hypotheses on human vision. We argue that, once on the surface, the human photopic (daytime) and scotopic (night-time) vision followed different evolutionary directions, maximum total energy, and optimum information, respectively. Our analysis also suggests that solar radiation reflected from the moon had little or no influence on the evolution of scotopic vision. Our results indicate that, apart from human vision, the vision of only a few birds, rodents, and deep-sea fish are strongly correlated to the available radiation within their respective habitats.

Trilogy Development of Proopiomelanocortin Neurons From Embryonic to Adult Stages in the Mice Retina

Proopiomelanocortin-positive amacrine cells (POMC ACs) were first discovered in adult mouse retinas in 2010; however, the development of POMC-ACs has not been studied. We bred POMC-EGFP mice to label POMC-positive cells and investigated the development of POMC neurons from embryonic to adult stages. We found that POMC neuron development is mainly divided into three stages: the embryonic stage, the closed-eye stage, and the open-eye stage. Each stage has unique characteristics. In the embryonic stage, POMC neurons appeared in the retina at about E13. There was a cell number developmental peak at E15, followed by a steep decline at E16. POMC neurons showed a large soma and increased spine numbers at the closed-eye stage, and two dendritic sublaminas formed in the inner plexiform layer (IPL). The appearance and increased soma size and dendrite numbers did not occur continuously in space. We found that the soma number was asymmetric between the superior and inferior retinas according to the developmental topographic map. Density peaked in the superior retina, which existed persistently in the retinal ganglion cell layer (GCL), but disappeared from the inner nuclear layer (INL) at about P6. At the same time, the soma distribution in the INL was the most regular. At the open-eye stage, the development of POMC neurons was nearly stable only with only an increase in the IPL width, which increased the soma–dendrite distance.

Physiological rhythms are influenced by photophase wavelength in a nocturnal and a diurnal rodent species from South Africa

The quality and quantity of light changes significantly over the course of the day. The effect of light intensity on physiological and behavioural responses of animals has been well documented, particularly during the scotophase, but the effect of the wavelength of light, particularly during the photophase, less so. We assessed the daily responses in urine production, urinary 6-sulfatoxymelatonin (6-SMT) and glucocorticoid metabolite (uGCM) concentrations in the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and diurnal four striped field mouse (Rhabdomys pumilio) under varying wavelengths of near monochromatic photophase (daytime) lighting. Animals were exposed to a short-wavelength light cycle (SWLC; ∼465-470 nm), a medium-wavelength light cycle (MWLC; ∼515-520 nm) and a long-wavelength light cycle (LWLC; ∼625-630 nm). The SWLC significantly attenuated mean daily urine production rates and the mean daily levels of urinary 6-SMT and of uGCM were inversely correlated with wavelength in both species. The presence of the SWLC greatly augmented overall daily 6-SMT levels, and simultaneously led to the highest uGCM concentrations in both species. In M. namaquensis, the urine production rate and urinary 6-SMT concentrations were significantly higher during the scotophase compared to the photophase under the SWLC and MWLC, whereas the uGCM concentrations were significantly higher during the scotophase under all WLCs. In R. pumilio, the urine production rate and uGCM were significantly higher during the scotophase of the SWLC, not the MWLC and LWLC. Our results illustrate that wavelength in the photophase plays a central role in the entrainment of rhythms in diurnal and nocturnal African rodent species.

Spatial sensitivity of human circadian response: Melatonin suppression from on-axis and off-axis light exposures

A better understanding of the spatial sensitivity of the human circadian system to photic stimulation can provide practical solutions for optimized circadian light exposures. Two psychophysical experiments, involving 25 adult participants in Experiment 1 (mean age = 34.0 years [SD 15.5]; 13 females) and 15 adult participants in Experiment 2 (mean age = 43.0 years [SD 12.6]; 12 females), were designed to investigate whether varying only the spatial distribution of luminous stimuli in the environment while maintaining a constant spectrally weighted irradiance at the eye could influence nocturnal melatonin suppression. Two spatial distributions were employed, one where the luminous stimulus was presented On-axis (along the line of sight) and one where two luminous stimuli were both presented Off-axis (laterally displaced at center by 14°). Two narrowband LED light sources, blue (λ_max  = 451 nm) for first experiment and green (λ_max  = 522 nm) for second experiment, were used in both the On-axis and the Off-axis spatial distributions. The blue luminous stimulus targeting the fovea and parafovea (On-axis) was about three times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis). The green luminous stimulus targeting the fovea and parafovea (On-axis) was about two times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis).

Mammalian Retinal Cell Quantification

Normal retina and its cell layers are essential for processing visual stimuli, and loss of its integrity has been documented in many disease processes. The numbers and the axonal processes of retinal ganglion cells are reduced substantially in glaucoma, leading to vision loss and blindness. Similarly, selective loss of photoreceptors in age-related macular degeneration and hereditary retinal dystrophies also results in the compromise of visual acuity. Development of genetically modified mice has led to increased understanding of the pathogenesis of many retinal diseases. Similarly, in this digital era, usage of modalities to quantify the retinal cell loss has grown exponentially leading to a better understanding of the suitability of animal models to study human retinal diseases. These quantification modalities provide valuable quantifiable data in studying pathogenesis and disease progression. This review will discuss the immunohistochemical markers for various retinal cells, available automated tools to quantify retinal cells, and present an example of retinal ganglion cell quantification using HALO image analysis platform. Additionally, we briefly review retinal cell types and subtypes, salient features of retina in various laboratory animal species, and a few of the main disease processes that affect retinal cell numbers in humans.

Visual adaptability and retinal characterization of the Egyptian fruit bat (Rousettus aegyptiacus, Pteropodidae): New insights into photoreceptors spatial distribution and melanosomal activity

Our study was conducted to characterize the retinal structure of the Egyptian fruit bat, Rousettus aegyptiacus to determine the distribution of photoreceptors and melanosomal populations in various retinal zones. Also, we paid attention to the specific structural and functional adaptations related to their nocturnal habits. We analyzed the retinae of 12 adult male Egyptian fruit bats using morphometrical, histological, ultrastructural, and immunoblotting standard techniques. Histological findings revealed that the retinal cells have variations in geometrical architecture and different retinal thickness together with their corresponding layers bearing specific choroidal papillae projecting towards the inner retina. Immunoblotting and ultrastructure results showed that the microstructure of the retina conforms to that pattern found in mammalian species. The retinal photoreceptors are rod-dominant; alternatively, possess two spectral types of cones: SWS and LW/MWS cones as evidence for the basis for dichromatic vision. In addition, the outer retina showed densely-distributed melanin granules with a significant increase in the number of pigment epithelium cells in the eccentric retina. Furthermore, the asymmetric distribution among the retinal quadrants for the visual pigments of both rods and cones coinciding with neuronal cells such as bipolar and ganglion cells confers instructive information about their visual perception and orientation. In conclusion, our findings indicate that R. aegyptiacus efficiently discriminates colors with complex visual adaptations to mediate increased visual acuity coopted for the nocturnal niches.

Spectral sensitivity of cone vision in the diurnal murid Rhabdomys pumilio

An animal's temporal niche - the time of day at which it is active - is known to drive a variety of adaptations in the visual system. These include variations in the topography, spectral sensitivity and density of retinal photoreceptors, and changes in the eye's gross anatomy and spectral transmission characteristics. We have characterised visual spectral sensitivity in the murid rodent Rhabdomys pumilio (the four-striped grass mouse), which is in the same family as (nocturnal) mice and rats but exhibits a strong diurnal niche. As is common in diurnal species, the R. pumilio lens acts as a long-pass spectral filter, providing limited transmission of light <400 nm. Conversely, we found strong sequence homologies with the R. pumilio SWS and MWS opsins and those of related nocturnal species (mice and rats) whose SWS opsins are maximally sensitive in the near-UV. We continued to assess in vivo spectral sensitivity of cone vision using electroretinography and multi-channel recordings from the visual thalamus. These revealed that responses across the human visible range could be adequately described by those of a single pigment (assumed to be MWS opsin) maximally sensitive at ∼500 nm, but that sensitivity in the near-UV required inclusion of a second pigment whose peak sensitivity lay well into the UV range (λmax<400 nm, probably ∼360 nm). We therefore conclude that, despite the UV-filtering effects of the lens, R. pumilio retains an SWS pigment with a UV-A λmax In effect, this somewhat paradoxical combination of long-pass lens and UV-A λmax results in narrow-band sensitivity for SWS cone pathways in the UV-A range.

nGnG Amacrine Cells and Brn3b-negative M1 ipRGCs are Specifically Labeled in the ChAT-ChR2-EYFP Mouse

Purpose

Experimental access to specific cell subtypes is essential for deciphering the complexity of retinal networks. Here, we characterized the selective labeling, caused by ectopic transgene expression, of two atypical retinal neurons in the ChAT-Channelrhodopsin-2 (ChR2)-EYFP mouse.

Methods

Retinal sections and flat-mounts were prepared for double-staining immunohistochemistry with antibodies against EYFP and various neuronal markers. Sagittal/coronal brain slices were made to visualize EYFP signals in central nuclei. Whole-cell recordings were conducted to test the functionality of ChR2.

Results

Two populations of EYFP-positive retinal cells were observed. The inner nuclear layer (INL)-located one (type I cell) distributed regularly throughout the entire retina, whereas the ganglion cell layer (GCL)-residing one (type II cell) was restricted ventrally. None of them was cholinergic, as evidenced by the complete absence of ChAT immunoreactivity. Type I cells were immunolabeled by the amacrine marker syntaxin. However, the vast majority of them were neither positive to GABA/GAD65, nor to GlyT1/glycine, suggesting that they were non-GABAergic non-glycinergic amacrine cells (nGnG ACs), which was confirmed by double-labeling with the nGnG AC marker PPP1R17. Type II cells were immunopositive to melanopsin, but not to Brn3a or Brn3b. They possessed dendrites stratifying in the outermost inner plexiform layer (IPL) and axons projecting to the suprachiasmatic nucleus (SCN) rather than the olivary pretectal nucleus (OPN), suggesting that they belonged to a Brn3b-negative subset of M1-type intrinsically photosensitive retinal ganglion cells (ipRGCs). Glutamatergic transmission-independent photocurrents were elicited in EYFP-positive cells, indicating the functional expression of ChR2.

Conclusions

The ChAT-ChR2-EYFP retina exhibits ectopic, but functional, transgene expression in nGnG ACs and SCN-innervating M1 ipRGCs, thus providing an ideal tool to achieve efficient labeling and optogenetic manipulation of these cells.

Effects of the colour of photophase light on locomotor activity in a nocturnal and a diurnal South African rodent

Many physiological and behavioural responses to varying qualities of light, particularly during the night (scotophase), have been well documented in rodents. We used varying wavelengths of day-time (photophase) lighting to assess daily responses in locomotor activity in the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and diurnal four-striped field mouse (Rhabdomys pumilio). Animals were exposed to three light-dark cycle regimes: a short-wavelength- (SWLC, blue), a medium-wavelength- (MWLC, green) and a long-wavelength light-dark cycle (LWLC, red). Overall, daily locomotor activity of both species changed according to different wavelengths of light: the diurnal species displayed most activity under the SWLC and the nocturnal species exhibited the highest levels of activity under the LWLC. Both species showed an increase in diurnal activity and a decrease in nocturnal activity under the LWLC. These results indicate an attenuated responsiveness to long-wavelength light in the nocturnal species, but this does not appear to be true for the diurnal species. These results emphasize that the effect of light on the locomotor activity of animals depends on both the properties of the light and the temporal organization of activity of a species.

Morphological alterations of intrinsically photosensitive retinal ganglion cells after ablation of mouse photoreceptors with selective photocoagulation

In this work, we investigated changes in the morphology of intrinsically photosensitive retinal ganglion cells (ipRGCs), M1 subtype, and pupillary light reflex following local and selective ablation of photoreceptors in mice. Laser photocoagulation was used to selectively destroy four patches of photoreceptors per eye at around 4 papillary diameters from the optic disc and at the 3, 6, 9, and 12 o'clock positions between the retinal vessels in the adult mouse retina, leaving cells in the inner retina intact. Morphological parameters of individual M1 cells specifically labeled by the antibody against melanopsin (PA1-780), including dendritic field size, total dendritic length, and dendritic branch number, were examined 1, 2, 4, and 8 weeks after photocoagulation with Neurolucida software. A considerable reduction in these parameters in M1 cells in the "lesioned areas" was found at all the four time points after photocoagulation, as compared with those in the "unlesioned areas". Although M1 cells in the lesioned areas showed significant changes as early as 1 week after laser treatment and the changes gradually increased, reaching a peak value at 2 weeks, morphological restoration was clearly seen in these cells over time. However, no difference in the morphological parameters of M1 cells was observed between the unlesioned areas of laser-treated mice and the corresponding areas of age-matched normal mice without laser lesions. Fluorescence intensity of the somata of melanopsin-positive M1 cells located inside the lesioned areas was significantly decreased at all the four time points after photocoagulation, whereas no changes in pupillary light reflex were detected at different light irradiations, indicating that photocoagulation-induced local photoreceptor loss and alterations of ipRGCs may be insufficient to cause abnormalities in non-image-forming (NIF) visual functions. The results suggest that intact photoreceptors could be crucial for maintaining the expression levels of melanopsin and normal morphology of M1 cells.