age-related changes in the daily rhythm of photoreceptor functioning and circuitry in a melatonin-proficient mouse strain与年龄相关的变化的日常节奏感光功能和电路melatonin-proficient鼠标应变.pdfVIP

Age-Related Changes in the Daily Rhythm of Photoreceptor Functioning and Circuitry in a Melatonin- Proficient Mouse Strain 1 2 1 1 2 Kenkichi Baba , Francesca Mazzoni , Sharon Owino , Susana Contreras-Alcantara , Enrica Strettoi , Gianluca Tosini1* 1 Circadian Rhythms and Sleep Disorders Program, Neuroscience Institute, Department of Anatomy and Neurobiology, Morehouse School of Medicine, CNR, Pisa, Italy, 2 Neuroscience Institute, Italian National Research Council, CNR, Pisa, Italy Abstract Retinal melatonin is involved in the modulation of many important retinal functions. Our previous studies have shown that the viability of photoreceptors and ganglion cells is reduced during aging in mice that lack melatonin receptor type 1. This demonstrates that melatonin signaling is important for the survival of retinal neurons. In the present study, we investigate the effects of aging on photoreceptor physiology and retinal organization in CH3-f+/+ mice, a melatonin proficient mouse strain. Our data indicate that the amplitude of the a and b waves of the scotopic and photopic electroretinogram decreases with age. Moreover, the daily rhythm in the amplitude of the a- and b- waves is lost during the aging process. Similarly, the scotopic threshold response is significantly affected by aging, but only when it is measured during the night. Interestingly, the changes observed in the ERGs are not paralleled by relevant changes in retinal morphological features, and administration of exogenous melatonin does not affect the ERGs in C3H-f+/+ at 12 months of age. This suggests that the responsiveness of the photoreceptors to exogenous melatonin is reduced during aging. Citation: Baba K, Mazzoni F, Owino S, Contreras-Al