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) 10 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 JCAuthor
Joseph C. Besharse PhD, MA Emeritus Professor in the Cell Biology Neurobiology and Anatomy department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsCircadian Rhythm
Dark Adaptation
Light
Male
Melatonin
Photoreceptor Cells
Sensory Thresholds
Xenopus
Xenopus laevis
