Dopamine Induces Optical Changes in the Cichlid Fish Lens

Abstract

The crystalline lens in the cichlid fish Aequidens pulcher undergoes a transformation of its optical properties every dawn and dusk as the eye adapts to changes in light conditions. During dusk the transformation result in an increase of the refractive power in the lens cortex, the outermost 40 percent. The change is thought to match the optical properties of the lens to the requirements of the retina. Using a short term in vitro lens culturing system together with optical measurements we here present data that confirm that the optical properties of the lens can change within hours and that dopamine influences the optical properties of the lens. Dopamine yields dose-dependent decrease of the refractive power in the lens cortex. The D1-agonist SKF-38393 induces a similar decrease of the refractive power in the cortex, while the D2-agonist quinpirole has no effect. The effect of dopamine can be blocked by using the D1-antagonist SCH 23390. Our results suggest that dopamine alone could be responsible for the light/dark adaptive optical changes in the lens, but the involvement of other signaling substances cannot be ruled out.

Evolution of the vertebrate beaded filament protein, Bfsp2; comparing the in vitro assembly properties of a “tailed” zebrafish Bfsp2 to its “tailless” human orthologue

“…Large size differences exist as well as lenses with short or long normalized focal lengths, that are monofocal or multifocal is different teleosts (Kröger et al, 2009). In cichlids, the lens has the property of changing its refractive power of the lens cortex in phase with light–dark cycles (Schartau et al, 2010). Interestingly, phosphorylation of Bfsp2 is a mechanism to alter the subcellular distribution of beaded filaments (Ireland et al, 1993) and so Bfsp2 and beaded filaments as well as lens crystallins (Kappe et al, 2010) are potential candidates to elicit such a change in lens refractive power.…”

Diurnal Variations in Ocular Aberrations of Human Eyes

“…However, the changes in anterior corneal curvature were not significantly associated with the changes in ocular spherical refraction (p40.05), which suggests that diurnal fluctuations in the other optical components of the eye, such as curvature of the crystalline lens or posterior cornea (or variations in the corneal or crystalline lens refractive index), could also be involved in the changes observed in the overall ocular refraction. Diurnal fluctuations in the gradient refractive index of the crystalline lens have been observed in other species, [66][67][68] and have been shown to be related to variations in retinal dopamine levels; however, diurnal changes in the refractive index of the human crystalline lens have not previously been examined. A limitation of the measurements in our current study is that the spherical refraction data was analyzed over a 5-mm pupil, but the anterior corneal keratometry values reflect only the central 2-3 mm of corneal curvature, which may have influenced the strength of the correlation observed between these variables.…”

Adaptation in the optical properties of the crystalline lens in the eyes of the Lessepsian migrantSiganus rivulatus

“…Beam paths were recorded with a digital video camera. The video sequences were processed using a custom-written program that detected the laser beams in the video footage [this program was tested in previous studies (Gagnon et al, 2008;Schartau et al, 2010a;Schartau et al, 2010b)]. For diagrams detailing the optical setup used in this study, see fig.2 in Kröger et al (Kröger et al, 1994) and fig.4 in Malkki and Kröger (Malkki and Kröger, 2005).…”