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Ageing and alpha 1 adrenoceptors in the iris
C Buckley1, D M Curtin, J Docherty
1Research Department, Royal Victoria Eye and Ear Hospital, Dublin.
Eye (London, England)
|January 1, 1987
Summary
Age-related pupil constriction, or miosis, is not due to changes in alpha-1 adrenoceptor sensitivity. This study found similar receptor responsiveness in both young and elderly individuals, ruling out age-related receptor alterations as a cause.
Area of Science:
- Ophthalmology
- Neuroscience
- Pharmacology
Background:
- Pupil size naturally decreases with age, a phenomenon known as age-related miosis.
- The sympathetic nervous system, particularly alpha-1 adrenoceptors, plays a role in pupil dilation.
- Previous research has not definitively linked age-related miosis to altered sympathetic adrenoceptor function.
Purpose of the Study:
- To investigate whether the age-related decrease in pupil size is caused by changes in sympathetic adrenoceptor responsiveness.
- To compare alpha-1 adrenoceptor sensitivity between young and elderly individuals.
Main Methods:
- Utilized logarithmic dose-response curves to assess adrenoceptor function.
- Employed phenylephrine (a selective alpha-1 agonist) and thymoxamine (a selective alpha-1 antagonist) to measure receptor sensitivity.
- Compared results between a cohort of young participants and a cohort of elderly participants.
Main Results:
- No significant difference in alpha-1 adrenoceptor sensitivity was observed between the elderly and young groups.
- Phenylephrine and thymoxamine dose-response curves were comparable across age groups.
- The study found no evidence of altered alpha-1 adrenoceptor responsiveness with advancing age.
Conclusions:
- Age-related miosis is not attributable to diminished alpha-1 adrenoceptor sensitivity.
- The underlying mechanisms of age-related pupil size reduction may involve other pathways.
- Alpha-1 receptor function remains stable throughout the adult lifespan, suggesting other factors contribute to age-related miosis.