The human eye expresses high levels of CB1 cannabinoid receptor mRNA and protein.

We used reverse transcriptase polymerase chain reaction to detect the expression of the central and peripheral cannabinoid receptors (CB1 and CB2, respectively) mRNA, and Western blotting to show the presence of the CB1 protein in subregions of the human eye. CB2 mRNA transcripts were undetectable, while levels of CB1 mRNA were significantly expressed in the human retina (25.8 +/- 2.46%), ciliary body (210 +/- 11.55%) and iris (62.7 +/- 5.94%) when compared with those of the normalizing reference gene beta2 microglobulin. The CB1 gene encodes a functional protein which is detected in its glycosylated (63 kDa) and unglycosylated (54 kDa) form in the same areas by a specific purified antibody raised against the amino terminus (residues 1-77) of the CB1 receptor. These results further support the proposed role of the CB1 receptor in controlling intraocular pressure, helping to explain the antiglaucoma properties of marijuana.