The effect of indomethacin on the Delta9-tetrahydrocannabinol (Delta9-THC)-induced fall in rabbit intraocular pressure (IOP) was determined. A 2% suspension of indomethacin was given topically 1 h before intravenous injection of Delta9-THC. IOP was measured hourly and was compared between groups receiving either Delta9-THC alone or Delta9-THC plus indomethacin. A substantial attenuation of the IOP response to Delta9-THC was caused by indomethacin. Delta9-THC may influence IOP at least in part by a prostaglandin-mediated process. Involvement of the cyclooxygenase pathway offers a common explanation for linking several ocular cannabinoid effects. The latter include a fall in IOP, conjunctival hyperemia and minor inflammation.
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