Spectral sensitivity of melatonin synthesis suppression in Xenopus eyecups. Vis Neurosci 1998;15(3):499-502
Date
07/31/1998Pubmed ID
9685202DOI
10.1017/s0952523898153099Scopus ID
2-s2.0-0032078074 (requires institutional sign-in at Scopus site) 8 CitationsAbstract
Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator and suppressed acutely by light. To identify photoreceptor mechanisms involved in the acute suppression of melatonin synthesis, an action spectrum was measured for dark-adapted Xenopus laevis eyecups at night. Intensity-response curves at six wavelengths from 400 to 650 nm were parallel, suggesting that a single photopigment predominates in melatonin suppression. Half-saturating intensities at 400, 440, 480, and 533 nm were not significantly different from one another, at 1-2 x 10(8) quanta cm(-2) s(-1). Significantly higher intensities of 580- and 650-nm light were required for melatonin suppression. These results indicate a predominant role for the principal green-absorbing rods in acute regulation of retinal melatonin synthesis in response to light, and argue against an important role for the red-absorbing cones. Higher than expected sensitivity at short wavelengths suggests that photoreceptors sensitive to blue and/or violet light may also contribute to melatonin suppression.
Author List
Cahill GM, Parsons SE, Besharse JCMESH terms used to index this publication - Major topics in bold
AnimalsCircadian Rhythm
Dark Adaptation
Light
Male
Melatonin
Photoreceptor Cells
Sensory Thresholds
Xenopus
Xenopus laevis
