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Impact of Retinal Stimulation on Neuromodulation
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Another recent research has demonstrated that many subtypes of each kind of retinal cell exist. For instance, three types of cones, L, M, and S, respond to long, medium, and short wavelengths of light, respectively. Bipolar cells are separated into midget and diffuse general groupings, with many subtypes of those, but, functionally, they are considered to be activated by central or surrounding targets. There are ON cone bipolar cells (for each type of cone cell grouping) and OFF cone bipolar cells as well as ON and OFF rod bipolar cells. As for the inhibitory horizontal and amacrine cells, three types of horizontal cells have been identified in the human retina as of 1994 (Ahnelt and Kolb 1994), and more than 20 kinds of amacrine cells are separated into wide and narrow field classifications. The most commonly researched of these cells are the starburst amacrine and the AII cells. The AII cells link some rod and cone information before signals exit the eye, and the starburst cells are involved in directional sensitivity involved by optokinetic reflexes (Yoshida et al. 2001).
The Biological Bases of Photoreception in the Process of Image Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
Amacrine cells are interneurons, involved in the analysis of visual signals before they leave the retina, mediating the lateral interconnections. They are lateral inhibitory interneurons which produce effects at the level of bipolar cell output synapses (reciprocal synapses onto bipolar cell synaptic terminals). Glycinergic amacrine cells are the narrow-field type (AII amacrine cells), and GABA-ergic amacrine cells are the wide-field type [Tsukamoto et al. 2017]. Both dendrites and the axon-like-processes of dopaminergic amacrine cells narrowly stratify close to the outer border of the inner plexiform layer, forming the “off” switch for the AII-mediated rod pathway. Morphological and physiological studies make it possible to identify about 30 types of amacrine cells. One of these is part of the pathway for rod vision (AII) briefly described above: from rod to bipolar cells to amacrine cells to ganglion cells. Another type responds strongly at the onset of a continuing visual signal, while still another one at the offset of a visual signal. Both responses fade quickly. Other amacrine cells, which are directionally sensitive, respond to the movement of a spot across the retina in a specific direction. A strong correlation was found between the number of amacrine cell synaptic contacts and the number of bipolar cell axonal ribbons. Formation of bipolar cell output at each ribbon synapse may be effectively regulated by a few nearby inhibitory inputs of amacrine cells. All the amacrine cells are connected to five of the six OFF bipolar cell types via chemical synapses and seven of the eight ON cone bipolar cell types via electrical synapses (gap junctions).[Tsukamoto et al. 2017]
Evaluation of potential health effects associated with occupational and environmental exposure to styrene – an update
Published in Journal of Toxicology and Environmental Health, Part B, 2019
M.I. Banton, J.S. Bus, J.J. Collins, E. Delzell, H.-P. Gelbke, J.E. Kester, M.M. Moore, R. Waites, S.S. Sarang
Vettori et al. (2000) examined the effect of subchronic styrene inhalation exposure on amacrine cells in female Sprague-Dawley rats. Amacrine cells, of which there are several dozen types, are interneurons that serve to integrate inputs from photoreceptors and modulate the visual message presented to retinal ganglion cells (Schwartz 2010; Witkovsky 2004). Vettori et al. (2000) focused on amacrine cells that release dopamine, the most abundant catecholamine in the vertebrate retina. Dopamine has multiple trophic roles related to eye growth, cell viability, circadian rhythmicity, and color perception (Kim, Chen, and Tannock 2014; Schwartz 2010; Tannock, Banaschewski, and Gold 2006; Witkovsky 2004). These neurons begin to die in aging animals, and reduction in retinal dopamine, such as occurs in Parkinson’s disease and attention-deficit/hyperactive disorder (ADHD), results in reduced visual contrast sensitivity (CS) and color vision deficits, particularly in blue-yellow pathways (Djamgoz et al. 1997; Firsov and Astakhova 2016; Popova 2014; Tannock, Banaschewski, and Gold 2006; Witkovsky 2004). Morphometric analysis of retinas from female Sprague-Dawley rats exposed to 300 ppm styrene 6 hours/day, 5 days/week, for 12 weeks (n = 10) showed a significant loss of tyrosine hydroxylase-immunoreactive (dopamine-producing) amacrine cells (Vettori et al. 2000). Dopamine and glutathione content were significantly lower in treated animals, and the activity of tyrosine hydroxylase was significantly higher when expressed as a function of the number of dopaminergic amacrine cells (Vettori et al. 2000). The potential human significance of these findings is unknown.