Abstract
Purpose: :
To determine age related changes in markers of sympathetic neurotransmission in 8, 22, and 32–month old rat retina.
Methods: :
Real time PCR and western blot analysis was conducted to investigate steady state mRNA and protein expression of ß1–adrenergic receptor, ß2–adrenergic receptor, and dopamine ß–hydroxylase in the retina of 8, 22, and 32–month old rats. Immunohistochemistry was performed to determine changes in dopamine–ß–hydroxylase localization.
Results: :
Steady state mRNA and protein expression of ß1–adrenergic receptor does not significantly change in the retina with age. Steady state mRNA expression of ß2–adrenergic receptor was significantly increased by 32 months as compared to 8 months (P<0.05). However, protein expression of ß2–adrenergic receptor did not change with increasing age. Gene expression for dopamine ß–hydroxylase is not altered. Protein expression of dopamine–ß–hydroxylase is observed to decrease with age throughout the retina.
Discussion: :
Decreases found in dopamine ß–hydroxylase protein expression suggest that less norepinephrine may be produced in the retina. We have previous data indicating that loss of sympathetic neurotransmission in the retina results in retinal pathology. Therefore, maintenance of normal adrenergic receptor neurotransmission appears to be important for retinal homeostasis. Based on these findings, ß2–adrenergic receptor agonists may be able to prevent, or possibly reverse, pathological changes in the retina that occur with age.
Keywords: aging • retinal degenerations: cell biology • neurotransmitters/neurotransmitter systems