Proparacaine hydrochloride eye drops alcaine

The sclera of guinea pigs is very thin, approximately 87 ± 11 µm (n = 5, measured in retinal frozen sections), so it cannot be assumed to heal reliably after intravitreal injections. In our experience, the injection site keeps open even one week after injection; therefore, subconjunctival injection is widely used for local drug application to ocular tissues in guinea pigs, even when the targets are located internally (e.g. retina).³⁴ (link)^,35 (link) For subconjunctival injections, stock solutions of the gap-junction antagonist, 18-β-GA (G10105; Sigma, Buchs, Switzerland), were prepared by mixing 0.85 mmol or 2.55 mmol 18-β-GA in 60 µL of 100% dimethyl sulfoxide (DMSO; D2650; Sigma) and stored at −20°C until use. These stock solutions were freshly diluted in double-distilled water (ddH₂O), just before use, to achieve the final concentrations designated “low-dose” (85 µM, 40 µg/100 µL) and “high-dose” (255 µM, 120 µg/100 µL) 18-β-GA. In the drug-injection groups, 100 µL of low- or high-dose solution or DMSO vehicle alone was injected subconjunctivally every day for 2 days or 4 weeks, after topical anesthesia with proparacaine hydrochloride eye drops (Alcaine; Alcon, Belgium). We used fine needles (26 or 30 gauge) and minimized injury and drug reflux by avoiding previous injection sites.