Table 2. .

Animals Were Treated with 1 mg/kg Morphine (IP) Followed by Retina Collection at Indicated Time Points

Untreated Eyes, Morphine (pg/mg protein)	Morphine-Treated Eyes, Morphine (pg/mg protein)
1–24 hours (n = 8)	1 hour (n = 8)	6 hours (n = 8)	24 hours (n = 8)
Not detectable	818,616 ± 62,387	454,504 ± 47,247	281,266 ± 28,249

Levels of morphine in retina samples were measured using an ELISA kit. Data are expressed as mean ± SE; n = 8. In each group, 4 rats (total 16 rats) were used in this experiment and each eye is represented as an individual observation (n = 8).