Cannabinoid receptor CB1 mRNA is highly expressed in the rat ciliary body: Implications for the antiglaucoma properties of marihuana

We used RT-PCR to measure relative differences in cannabinoid receptor (CB) mRNAs in the rat eye, comparing CB1 or CB2 transcripts to that of the normalizing reference gene β2 microglobulin (β2m). Significantly higher levels of CB1 mRNA levels were found in the ciliary body (0.84 ± 0.05% of β2m) than in the iris, (0.34 ± 0.04% of β2m), retina (0.07 ± 0.005% of β2m) and choroid (0.06 ± 0.005% of β2m). CB2 mRNA was undetectable. This expression pattern supports a specific role for the CB1 receptor in controlling intraocular pressure, helping to explain the antiglaucoma property of cannabinoids.