Author: Gianpiero Pescarmona
Date: 06/03/2008


Eyes are organs that detect light

Open Question: how eyes developed during fetal life in the absence of light?

The human eye contains two types of receptors that respond to light: cones and rods.

Open Question: why the sensors cells how eyes developed during fetal life in the absence of light?

Retinal pigments

Different Organisms See Different Worlds

Fish Vision

Human eye

Eye color vision

Human cones come in three varietys, indentified as S, M, and L, that are sensitive to short, medium, and long wavelengths of light, respectively.

S 445 nm blue light
M 540 nm green
L 565 nm red

The L cones are most abundant (63%), followed by M cones (31%) and a small number of S cones (6%).

Bipolar cell pathways in the vertebrate retina, 2007

Int J Neurosci. 1998 Jul;95(1-2):115-32.
Excitatory amino acids and serotonin uptake blockers reveal two physiologically distinct serotonin systems in the retina of the skate, Raja erinacea.

Schuette E, Chappell RL.

Hunter College and the Graduate School of the City University of New York, Department of Biological Sciences, NY 10021, USA.

The retina of the skate (Raja erinacea) contains at least 2 types of cell (amacrines and bipolars) that can be visualized with an antiserum against serotonin. We have employed serotonin immunocytochemistry in combination with pharmacological manipulation of retinal tissue to analyze physiological properties of serotonergic amacrine cells and serotonin-accumulating bipolar cells. Excitatory amino acids (NMDA, aspartate) had no detectable effects on serotonin-immunoreactivity in bipolar cells but decreased staining in amacrine cells. High K+ Ringer increased staining in bipolar cell somata, however, it depleted the inner plexiform layer of the retina of serotonin. Zimelidine, a serotonin uptake inhibitor, completely blocked serotonin accumulation by bipolar cells but had no effect on amacrine cells, whereas incubation of the retinas in fluoxetine (Prozac), a different inhibitor of serotonin uptake, did not block serotonin accumulation into bipolar cells which was actually enhanced in some cases. We conclude that amacrine and bipolar cells of the skate retina employ two different serotonin uptake carrier systems, thus generating two distinct pharmacological components that are capable of interacting with each other as they compete for extracellular serotonin. Similar mechanisms may exist in the vertebrate CNS and further examination of the interaction of these systems could provide important insights into the action and possible side effects of serotonin-related drugs.

Brain Res Mol Brain Res. 1998 Oct 30;61(1-2):243-50.
Circadian expression of tryptophan hydroxylase mRNA in the chicken retina.

Chong NW, Cassone VM, Bernard M, Klein DC, Iuvone PM.

National Institutes of Health Section on Neuroendocrinology, Laboratory of Developmental Neurobiology, 49/5A38, National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.

Many aspects of retinal physiology are controlled by a circadian clock located within the eye. This clock controls the rhythmic synthesis of melatonin, which results in elevated levels during the night and low levels during the day. The rate-limiting enzyme in melatonin biosynthesis in retina appears to be tryptophan hydroxylase (TPH)[G.M. Cahill and J.C. Besharse, Circadian regulation of melatonin in the retina of Xenopus laevis: Limitation by serotonin availability, J. Neurochem. 54 (1990) 716-719]. In this report, we found that TPH mRNA is strongly expressed in the photoreceptor layer and the vitread portion of the inner nuclear layer; the message is also expressed, but to a lesser extent, in the ganglion cell layer. The abundance of retinal TPH mRNA exhibits a circadian rhythm which persists in constant light or constant darkness. The phase of the rhythm can be reversed by reversing the light:dark cycle. In parallel experiments we found a similar pattern of expression in the chicken pineal gland. However, whereas a pulse of light at midnight suppressed retinal TPH mRNA by 25%, it did not alter pineal TPH mRNA, suggesting that there are tissue-specific differences in photic regulation of TPH mRNA. In retinas treated with kainic acid to destroy serotonin-containing amacrine and bipolar cells, a high amplitude rhythm of TPH mRNA was observed indicating that melatonin-synthesizing photoreceptors are the primary source of the rhythmic message. These observations provide the first evidence that chick retinal TPH mRNA is under control of a circadian clock. Copyright 1998 Elsevier Science B.V.

bipolar cells retina serotonin

Eye neurons

MIT eye research

Pigmented layer

Differential response of red and green cones

S-Potentials and Horizontal Cells

Reference Textbooks

Webvision: The Organization of the Retina and Visual System - book thumbnail

Webvision: The Organization of the Retina and Visual System 2007

Eye Diseases

from Injectable_hydrogels_for_ophthalmic_applications, 2017

2010-07-14T13:54:34 - Gianpiero Pescarmona


Sofferenza retinica.IT

Clinical Report: after cataract surgery

Retinal Edema

Anatomical Retinal info

Retinal Physiology

Optical coherence tomography OCT


Intravitreal triamcinolone for macular detachment following panretinal photocoagulation 2005

Caso Clinico

2008-09-15T17:29:36 - vanessa arcuri

Transformation of cone precursors to functional rod photoreceptors by bZIP transcription factor NRL 2007

During the embryogenesis, the neuroectoderm forms the external and the inner layer of the retina. The external layer then turns into the inner pigmented layer of the retina.
The inner layer generates the nervous layer of retina.
During the 7th week of pregnancy the optic nerve is born, followed by the retinal cells.
However the eyelids remain closed until the 26th week

Recent studies show that baby’s eyes are sensitive to light while he is still in the mother’s womb.
If a light is projected to the mother’s abdomen during the 7th month of pregnancy, it can be seen though ultrasound scan that the foetus reacts to the light by closing the eyelids.

A recent publication (Sale et al. 2007) proves the importance of environmental enrichment during foetal life.
The study demonstrates showed that prenatal enrichment plays an important rule in the foetal retinal development.
During the embryonic life, the environmental conditions have a significant impact on central nervous system development.
The environmental enrichment accelerates the cell death (apoptosys) of foetal RGCs (Retinal Ganglion Cells). As a matter of fact, the retinal ganglion cell death exerts the environmental effects on the foetus and they are mediated by the mother: this is a key role in sculpturing the developing retinal system at prenatal ages.
The migration acceleration of neuronal progenitors and the dynamics of neural cells death seem to be under the control of Insuline-like Growth Factor (IGF-I): its levels, higher in enriched pregnant rats and in their milk, are increased also in their offspring, its neutralization abolishes the maternal enrichment on retinal development and chronic IGF-I injection to standard-reared females mimics the effects of enrichment in the foetuses.
The possibility that maternal exposure to conditions of increased sociality and sensory-motor activity might influence the embryonic development remain unexplored.

These findings could orientate clinical research in the field of prenatal therapy.

Berardi N, Pizzorusso T, Ratto GM, Maffei L (2003) Molecular basis of plasticity
visual cortex. Trends Neurosci 26:369-378.
Cancedda L, Putignano E, Sale A, Viegi A, Berardi N, et al (2004)
Acceleration of visual system development by environmental enrichment

Isenmann S, Kretz A, Cellerino A (2003) Molecular determinants of retinal ganglion cell development, survival, and regeneration. Prog Retin Eye Res 22:483-543.
Landi S, Sale A, Berardi N, Viegi A, Maffei L, Cenni MC (2007)
Retinal functional development is sensitive to environmental enrichment: a role for BDNF. 2007

FASEB J 21: 130-139


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