Tetrodotoxin: Effects on Fish and Frog Melanophores

Fujii, Ryozo; Novales, Ronald R.

doi:10.1126/science.160.3832.1123

Cited by 29 publications

(14 citation statements)

References 9 publications

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“…In another retinal mutant, noa, in which there appears to be a failure of synaptic transmission, the melanophores are chronically expanded (Brockerhoff et al, 1995). The pigmentation of melanophores is controlled both by neural input to the cells and by circulating neural hormones (Ujii and Novales, 1968;Bagnara, 1972). Melanin granules in zebrafish melanophores aggregate in the light and disperse in the dark, causing darkening of zebrafish at night and blanching during the day.…”

Section: Discussionmentioning

confidence: 99%

A New Form of Inherited Red-Blindness Identified in Zebrafish

et al. 1997

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A red-blind zebrafish mutant, partial optokinetic response b (pob), has been isolated by measuring eye movements of larvae in a three-generation screen for recessive mutations affecting the visual system. pob larvae exhibit eye movements in response to rotating black and white stripes illuminated with white light, but they do not move their eyes when the stripes are illuminated with red light. Physiological, immunohistochemical, and in situ hybridization analyses of pob retinas showed a selective loss of red-sensitive cones at 5 days postfertilization (dpf ). At 3 dpf, cells expressing red opsin are present, suggesting that red-sensitive cones form initially but then disappear rapidly, whereas other photoreceptors remain. Linkage analysis indicated that the mutation identified in the pob mutant is not at the red opsin locus. Because red opsin is the only known molecule unique to red cones, these data suggest that a novel gene is required for the maintenance or function of red cones. Key words: zebrafish; retina; red opsin; vision; behavior; mutantWe have initiated a genetic analysis of zebrafish (Danio rerio) so that we can use its sophisticated visual system to identify genes required for normal vertebrate visual responses. Zebrafish are tetrachromatic; in addition to rods, their retinas contain four types of cones that absorb light maximally in the red (570 nm), green (480 nm), blue (415 nm), and UV (362 nm) regions of the spectrum . Early in development, zebrafish vision is primarily photopic, and it is not until 12 days postfertilization (dqf ) that scotopic visual behavior is measurable (Clark, 1981;Branchek, 1984). In adults, the cones are arranged in a row mosaic (Branchek and Bremiller, 1984;Robinson et al., 1993); red-and green-sensitive cones alternate in sequence and are separated by either a single blue cone (always adjacent to a red-sensitive cone) or a single UV cone (always adjacent to a green-sensitive cone) . Red opsin expression begins at ϳ52 hr postfertilization, followed by blue and then by UV opsin (Raymond et al., 1995) (E. Schmitt and J. Dowling, unpublished observation). By ϳ3 dpf, zebrafish have opsinexpressing cones distributed throughout the photoreceptor layer of the retina.We described earlier how a rapid behavioral assay based on the optokinetic response (OKR) can be used to isolate zebrafish larvae with vision defects but with no obvious external morphological abnormalities (Brockerhoff et al., 1995). Zebrafish larvae, by 5 dpf, reliably display smooth pursuit and saccade eye movements in response to illuminated rotating stripes (see http:// weber.u.washington.edu/ϳjbhurley/ Movies.html for a demonstration of the OKR). As a secondary assay, we record the electroretinogram (ERG) from fish that lack an OKR to determine whether the defect resides in the outer retina. Using these two assays we have been able to isolate visual mutants with subtle retinal defects.In this study we conducted a similar screen using the same behavioral assay; however, we specifically searched for recessive m...

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Section: Discussionmentioning

confidence: 99%

A New Form of Inherited Red-Blindness Identified in Zebrafish

et al. 1997

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“…In the killifish Fundulus heteroclitus, Fujii and Novales (1968) showed that tetrodotoxin effectively blocked the conduction of melanin-aggregating fibers, but not the responsiveness of melanophores per se. Their results also indicated that Na + -dependent action potentials are not involved in the responsiveness of the effector cells.…”

Section: Other Chemical Factors Influencing Chromatophoresmentioning

confidence: 99%

“…Fujii (1961) also found that the effect of K + ions could be blocked by treatment with the adrenergic blocking agent dibenamine. Furthermore, Fujii and Novales (1968) showed that the response to K + ions could still be observed after treatment with tetrodotoxin, which effectively blocked the conduction of pigment-aggregating nerves. The results also indicated that active electrical events due to the entry of Na + ions are not involved in the motile activity of the cells.…”

Section: Substances That Modify Hormonal and Nervous Signalsmentioning

confidence: 99%

Factors Influencing Motile Activities of Fish Chromatophores

Fujii

Oshima

1994

Advances in Comparative and Environmental Physiology

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“…It is known that such an electrical field stimulates sympathetic fibers to liberate neurotransmitters (Fujii and Novales, 1968). The stimulating waves were monitored by a storage oscilloscope (5111A, Tektronix, Beaverton, OR).…”

Section: Nervous Stimulationmentioning

confidence: 99%