Purpose: To investigate expression of muscarinic, cholinergic, and adrenergic receptors on developing conjunctival goblet cells.
Methods: Eyes were removed from rats 9 to 60 days old, fixed, and used for microscopy. For glycoconjugate expression, sections were stained with Alcian blue/periodic acid-Schiffs reagent (AB/PAS) and with the lectins Ulex europeus agglutinin I (UEA-I) and Helix pomatia agglutinin (HPA). Goblet cell bodies were identified using anti-cytokeratin 7 (CK7). Nerve fibers were localized using anti-protein gene product 9.5. Location of muscarinic and adrenergic receptors was investigated using anti-muscarinic and beta-adrenergic receptors.
Results: At days 9 and 13, single apical cells in conjunctival epithelium stained with AB/PAS, UEA-I, and CK7. At days 17 and 60, increasing numbers of goblet cells were identified by AB/PAS, UEA-I, HPA, and CK7. Nerve fibers were localized around stratified squamous cells and at the epithelial base at days 9 and 13, and around goblet cells and at the epithelial base at days 17 and 60. At days 9 and 13, M2- and M3-muscarinic and beta2-adrenergic receptors were found in stratified squamous cells, but M1-muscarinic and beta1-adrenergic receptors were not detected. At days 17 and 60, M2- and M3-muscarinic receptors were found in goblet cells, whereas M1-muscarinic receptors were in stratified squamous cells. Beta1- and beta2-adrenergic receptors were found on both cell types. Beta3-adrenergic receptors were not detected.
Conclusions: In conjunctiva, nerves, M2- and M3-muscarinic, and beta1- and beta2-adrenergic receptors are present on developing goblet cells and could regulate secretion as eyelids open.