Chronic clorgyline dampens rat retinal rhythms.

Area of Science:

• Chronobiology
• Neuroscience
• Ophthalmology

Background:

• Circadian rhythms govern physiological processes, including disk shedding in the rat retina and organelle degradation in inner segments.
• The monoamineoxidase inhibitor clorgyline is known to phase-delay circadian rhythms in rodents.
• The effect of clorgyline on retinal circadian rhythms, specifically disk shedding and autophagic activity, requires further investigation.

Purpose of the Study:

• To investigate the impact of clorgyline on the circadian rhythm of disk shedding in the rat retina.
• To determine if clorgyline affects the circadian rhythm of autophagic degradation in retinal inner segments.
• To elucidate the role of intraocular oscillators versus external light cues in regulating retinal circadian rhythms.

Main Methods:

• Rats were administered clorgyline chronically.
• Circadian rhythms of retinal disk shedding and autophagic vacuoles were monitored under different light-dark cycles and constant darkness.
• Plasma corticosterone levels were measured.

Main Results:

• Clorgyline did not phase-delay the retinal disk-shedding rhythm under light-dark or constant dark conditions, only reducing its amplitude.
• A significant reduction in the amplitude of autophagic vacuoles rhythm was observed after chronic clorgyline treatment.
• Plasma corticosterone rhythm was unaffected in phase by clorgyline.

Conclusions:

• The circadian rhythm of disk shedding in the rat retina is primarily regulated by an intrinsic ocular oscillator.
• Clorgyline modulates the light response of retinal parameters but does not alter the timing of these circadian rhythms.
• Autophagic activity in retinal inner segments is also sensitive to clorgyline, suggesting complex interactions within retinal circadian regulation.