α₂-Adrenergic Receptors Are Present in Normal Human Conjunctiva

Abstract

Purpose: Despite the passage of medications, including antiglaucoma drugs, through the ocular surface, and despite the increasing relevance of neurogenic inflammation in the ocular surface, the presence of some neuroreceptors in the conjunctiva has not been ascertained. This study describes the presence of α₂-adrenergic receptors in normal human conjunctiva. Methods: Immunofluorescence microscopy, electrophoresis, and Western blot analyses were done in human conjunctival biopsies and rat control tissues. Antibodies against α₂-adrenergic receptor subtypes α_2A, α_2B, and α_2C were used. Results: Immunoreactivity for α_2A- and α_2B-, but not α_2C-adrenergic receptors was evenly distributed in epithelial cells of human conjunctiva cryosections. Immunoreactive bands were detected for the three α₂-adrenergic receptor subtypes: a major band of 48–50 kDa and fellow bands of 65–67 kDa. Conclusions: Normal human conjunctival epithelial cells express α_2A-, α_2B-, and α_2C-adrenergic receptors. Further studies to determine the functional implications of these receptors in ocular surface homeostasis are warranted.

KEYWORDS:

• adrenergic receptors
• confocal microscopy
• conjunctiva
• glaucoma
• sympathetic autonomous system