PubMed · 4566953
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J R Bourne, P R Hudak, J L Duke. 1972. Computer automated electrooculography.. https://doi.org/10.1016/0010-4809(72)90044-4
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PURPOSE: To study the histology and the physiological function of the retina in the neurological myelin mutant, taiep rats during the postnatal developmental period (P20-P360). METHODS: Electroretinography (ERG) was applied to evaluate intensity dependence and spectral sensitivity of the responses to light. Retinal histology, morphometry, and immunocytochemistry were used to characterize the structure of the retina, with particular emphasis on the Müller (glial) cells. RESULTS: In the taiep rats of all ages studied, the scotopic ERG showed normal a- and b-wave amplitudes and latencies; likewise, the scotopic spectral sensitivity function was the same for control and taiep animals, with a maximal sensitivity (lambda(max)) at 500 nm. However, in adult taiep rats (P90 to P360) a secondary cornea-positive wave ('b(2)') was observed in response to high stimulus intensities, which never occurred in controls. This correlated with the observation that in the photopic ERG responses of the taiep rats, the b-wave was reduced in amplitude, and was followed by a rapid cornea-negative after-potential. After 1 year of life, in taiep rats the outer plexiform layer (OPL) became slightly thinner and the inner plexiform/ganglion cell layers (IPL/GCL) appeared to be swollen, and increased in thickness; in addition, the number of retinal neurons (particularly, of photoreceptor cells) slightly decreased. Increased GFAP immunoreactivity revealed a hypertrophy and reactivity of the Müller cells in 1-year-old taiep rats. CONCLUSIONS: The present results suggest the occurrence of a relatively mild and slowly progressing neural retinal alteration in taiep rats, which becomes histologically and functionally evident at the end of the first year of life, and mainly affects the circuit(s) of the photopic ON-response. It is speculated that this alteration is due to missing/altered signals from demyelinated optic nerve.
Transducins couple visual pigments to cGMP hydrolysis, the only recognized phototransduction pathway in vertebrate photoreceptors. Here we describe a zebrafish mutant, no optokinetic response f(w21) (nof), with a nonsense mutation in the gene encoding the alpha subunit of cone transducin. Retinal morphology and levels of phototransduction enzymes are normal in nof retinas, but cone transducin is undetectable. Dark current in nof cones is also normal, but it is insensitive to moderate intensity light. The nof cones do respond, however, to bright light. These responses are produced by a light-stimulated, but transducin-independent, release of Ca2+ into the cone cytoplasm. Thus, in addition to stimulating transducin, light also independently induces release of Ca2+ into the photoreceptor cytoplasm.
In the mammalian retina, a small subset of retinal ganglion cells (RGCs) are intrinsically photosensitive, express the opsin-like protein melanopsin, and project to brain nuclei involved in non-image-forming visual functions such as pupillary light reflex and circadian photoentrainment. We report that in mice with the melanopsin gene ablated, RGCs retrograde-labeled from the suprachiasmatic nuclei were no longer intrinsically photosensitive, although their number, morphology, and projections were unchanged. These animals showed a pupillary light reflex indistinguishable from that of the wild type at low irradiances, but at high irradiances the reflex was incomplete, a pattern that suggests that the melanopsin-associated system and the classical rod/cone system are complementary in function.