Abstract
Purpose: :
The traditional and most widely used technique for studying rabbit lacrimal gland secretory function in vivo has been to inject a drug intravenously. However, one inevitable and often intolerable side effect is the systemic influence of the drug being studied. Here we report a new and local approach in administering drug through the ocular cavity, with minimal systemic side effects.
Methods: :
After the rabbit is anesthetized, the eyeball is rotated to the superior side by a suture. Inferior bulbar conjunctiva and underlying connective tissue are blunt dissected until reaching the membrane overlying the deep ocular cavity where the inferior lacrimal gland resides. A small puncture is made through the membrane and 1.5 mm OD polyethylene tubing is inserted through this puncture, thus making the inferior orbital floor a sealed space where drug is retained. The tubing is connected to a syringe for drug delivery. The contralateral eye is similarly prepared, but only saline is delivered into the cavity to serve as control. The main lacrimal gland excretory ducts are cannulated with 0.61 mm OD polyethylene tubing that has been pretreated with protease inhibitor, and lacrimal fluid is collected in centrifuge tubes.
Results: :
Pilocarpine induced significant amounts of lacrimal fluid secretion from the lacrimal gland that had been locally perfused, with no noticeable effect on the contralateral gland. There was no increased salivary secretion, as observed by visual inspection, whereas pilocarpine administered intravenously is accompanied by a flush of saliva that occasionally chokes the animal. Lacrimal fluid was collected for 3×10 minutes, after which drug delivery was terminated and the animal was allowed to recover until the secretion rate of the experimental gland returned to that of the control side. The procedure was then reversed, i.e., pilocarpine was administered to the control gland while the experimental gland used before served as control. Pilocarpine caused greatly increased lacrimal fluid secretion from the gland, without noticeable effect on the contralateral gland, i.e., exactly duplicating the results before switching the glands. Other drugs are now being tested.
Conclusions: :
Our preliminary studies have demonstrated that this local approach in administering drugs into the ocular cavity avoids the unwanted systemic effects of intravenous injection that can complicate the experimental results, and in some instances can make it impossible to interpret the data. This novel, targeted and unique local approach is a promising new technique to study the in vivo lacrimal gland secretion.
Keywords: lacrimal gland • cornea: tears/tear film/dry eye • clinical research methodology