A dark decrement for enhanced dynamic sensitivity of retinal photoreceptors

“Non-image-forming” (NIF) effects of light are mediated primarily by a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment, melanopsin (OPN4). These NIF functions include circadian entrainment, pupillary reflexes, and photic effects on sleep, mood, and cognition. We recently reported that mice of multiple genotypes exhibit reduced voluntary ethanol intake under both constant darkness (DD) and constant light (LL) relative to standard light-dark (LD) conditions. In the present study, we sought to determine whether these effects are mediated by melanopsin-expressing ipRGCs and their potential relationship to photic effects on the circadian system. To this end, we examined the effects of environmental lighting regimen on both ethanol intake and circadian activity rhythms in a genetically engineered mouse model ( Opn4aDTA/aDTA) in which melanopsin expression is completely blocked while ipRGCs are progressively ablated due to activation of attenuated diphtheria toxin A (aDTA) transgene under the control of the Opn4 promoter. As expected from previous studies, Opn4aDTA/aDTA mice displayed dramatic attenuation of circadian photosensitivity, but surprisingly, showed identical suppression of ethanol intake under both DD and LL as that seen in controls. These results demonstrate that the effects of lighting regimen on voluntary ethanol intake are independent of melanopsin-expressing ipRGCs and ipRGC-mediated photic effects on the circadian system. Rather, these effects are likely mediated by classical retinal photoreceptors and central pathways.

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Metabolism in the Zebrafish Retina

Journal of Developmental Biology ◽

10.3390/jdb9010010 ◽

2021 ◽

Vol 9 (1) ◽

pp. 10

Author(s):

Natalia Jaroszynska ◽

Philippa Harding ◽

Mariya Moosajee

Keyword(s):

Pigment Epithelium ◽

Retinal Pigment ◽

The Body ◽

Therapeutic Approaches ◽

Retinal Photoreceptors ◽

Sufficient Energy ◽

Metabolic Products ◽

Sight Loss ◽

Choroidal Vasculature ◽

The Brain

Retinal photoreceptors are amongst the most metabolically active cells in the body, consuming more glucose as a metabolic substrate than even the brain. This ensures that there is sufficient energy to establish and maintain photoreceptor functions during and after their differentiation. Such high dependence on glucose metabolism is conserved across vertebrates, including zebrafish from early larval through to adult retinal stages. As the zebrafish retina develops rapidly, reaching an adult-like structure by 72 hours post fertilisation, zebrafish larvae can be used to study metabolism not only during retinogenesis, but also in functionally mature retinae. The interplay between rod and cone photoreceptors and the neighbouring retinal pigment epithelium (RPE) cells establishes a metabolic ecosystem that provides essential control of their individual functions, overall maintaining healthy vision. The RPE facilitates efficient supply of glucose from the choroidal vasculature to the photoreceptors, which produce metabolic products that in turn fuel RPE metabolism. Many inherited retinal diseases (IRDs) result in photoreceptor degeneration, either directly arising from photoreceptor-specific mutations or secondary to RPE loss, leading to sight loss. Evidence from a number of vertebrate studies suggests that the imbalance of the metabolic ecosystem in the outer retina contributes to metabolic failure and disease pathogenesis. The use of larval zebrafish mutants with disease-specific mutations that mirror those seen in human patients allows us to uncover mechanisms of such dysregulation and disease pathology with progression from embryonic to adult stages, as well as providing a means of testing novel therapeutic approaches.

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Sensitivity with Respect to the Path Parameters and Nonlinear Stiffness of Vibration Transfer Path Systems

Mathematical Problems in Engineering ◽

10.1155/2010/650247 ◽

2010 ◽

Vol 2010 ◽

pp. 1-11

Author(s):

Yimin Zhang ◽

Xianzhen Huang

Keyword(s):

Dynamic Response ◽

Time Domain ◽

Evaluation Criteria ◽

Nonlinear Stiffness ◽

Vibration System ◽

Transfer Path ◽

Dynamic Sensitivity ◽

The Time Domain

Generally speaking, a vibration system consists of three parts: vibration resource, vibration transfer path, and vibration receiver. Based on the dynamic sensitivity technique, this paper proposes a method for evaluating the contribution of each vibration transfer path to the dynamic response of the vibration receiver. Nonlinear stiffness is an important factor in causing the nonlinearity of vibration systems. Taking sensitivity as the evaluation criteria, we present an effective approach for estimating the influence of nonlinear stiffness in vibration transfer paths on the dynamic response of the vibration receiver. Using the proposed method, the sensitivity of the vibration system with multiple and/or multidimensional transfer paths could be determined in the time domain.

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EFFECTS OF LIGHT ON CYCLIC GMP METABOLISM IN RETINAL PHOTORECEPTORS

Journal of Neurochemistry ◽

10.1111/j.1471-4159.1976.tb10399.x ◽

1976 ◽

Vol 27 (3) ◽

pp. 717-722 ◽

Cited By ~ 57

Author(s):

G. Krishna ◽

N. Krishnan ◽

R. T. Fletcher ◽

G. Chader

Keyword(s):

Cyclic Gmp ◽

Retinal Photoreceptors

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Proportion of muscles spindles supplied by skeletofusimotor axons (beta-axons) in peroneus brevis muscle of the cat

Journal of Neurophysiology ◽

10.1152/jn.1975.38.6.1390 ◽

1975 ◽

Vol 38 (6) ◽

pp. 1390-1394 ◽

Cited By ~ 117

Author(s):

F. Emonet-Denand ◽

Y. Laporte

Keyword(s):

Neuromuscular Junctions ◽

Muscle Fibers ◽

Repetitive Stimulation ◽

Motor Axon ◽

Dynamic Sensitivity ◽

Conduction Velocities ◽

Peroneus Brevis ◽

Stimulation Of

Of 32 cat peroneus brevis spindles, 23 (72%) were found to be supplied by a least 1 skeletofusimotor or beta-axon. A motor axon was identified as skeletofusimotor when repetitive stimulation of it elicited both the contraction of extrafusal muscle fibers and as acceleration of the discharge of primary ending, which persisted after selective block of the neuromuscular junctions of extrafusal muscle fibers. The block was obtained by stimulating single axons at 400-500/s for a few seconds. Of 135 axons supplying extrafusal muscle fibers, 24 (18%) were shown to be beta-axons; 22 beta-axons had conduction velocities ranging from 45 to 75 m/s. All but three beta-axons increased the dynamic sensitivity of primary endings. Beta-innervated spindles may also be supplied by dynamic gamma-axons.

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Insect photoreceptor adaptations to night vision

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2016.0077 ◽

2017 ◽

Vol 372 (1717) ◽

pp. 20160077 ◽

Cited By ~ 18

Author(s):

Anna Honkanen ◽

Esa-Ville Immonen ◽

Iikka Salmela ◽

Kyösti Heimonen ◽

Matti Weckström

Keyword(s):

Visual Information ◽

Insect Vision ◽

Night Vision ◽

Single Photons ◽

Visually Guided ◽

Neural Signals ◽

Light Responses ◽

Anatomical Structures ◽

Retinal Photoreceptors ◽

Physiological Adaptations

Night vision is ultimately about extracting information from a noisy visual input. Several species of nocturnal insects exhibit complex visually guided behaviour in conditions where most animals are practically blind. The compound eyes of nocturnal insects produce strong responses to single photons and process them into meaningful neural signals, which are amplified by specialized neuroanatomical structures. While a lot is known about the light responses and the anatomical structures that promote pooling of responses to increase sensitivity, there is still a dearth of knowledge on the physiology of night vision. Retinal photoreceptors form the first bottleneck for the transfer of visual information. In this review, we cover the basics of what is known about physiological adaptations of insect photoreceptors for low-light vision. We will also discuss major enigmas of some of the functional properties of nocturnal photoreceptors, and describe recent advances in methodologies that may help to solve them and broaden the field of insect vision research to new model animals. This article is part of the themed issue ‘Vision in dim light’.

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