Aging affects the ocular circadian pacemaker of Aplysia californica

The eye of Aplysia has been used to explore various aspects of circadian rh ythms. The authors discovered that age has profound effects on the circadia n rhythm of nerve impulses from the eye. With age, there was a significant decrease in the amplitude of the rhythm. The decrease appeared to be contin uous over the Life span of the animal and was observed both in vitro and in vivo. The free-running period and phase angle of the rhythm steadily incre ased with age, indicating that the pacemaker itself was affected by age. Ra tes of transcription and translation were significantly increased with age, suggesting that age-associated alterations of the pacemaker may occur thro ugh changes in macromolecular synthesis. Interestingly, eyes from some olde r (greater than or equal to 10 months) animals had "cloudy" lenses (catarac ts). Highly damped or arrhythmic rhythms always were seen in eyes with clou dy lenses. Morphology of eyes with cloudy lenses indicated severe retinal d egeneration. No such degeneration was observed in eyes with clear lenses th at were used in the analysis of the rhythm with age.