Ocular hypotensive effects of an intratracheally delivered liposomal delta9-tetrahydrocannabinol preparation in rats.
This study investigated the effect of an intratracheal (i.t.) administration of a liposome-entrapped Delta9-tetrahydrocannabinol (LTHC) preparation on intraocular pressure (IOP) in nonanaesthetized Brown Norway rats. The ocular hypotensive effects of i.t. LTHC were compared to that of intraperitoneal (i.p.) LTHC administration. All i.t. LTHC doses >0.05 mg/kg significantly decreased IOP (P < 0.05) within 30 min of administration, and doses of i.t. LTHC >0.1 mg/kg decreased IOP within 15 min of administration. A maximal reduction in IOP of 2.32 +/- 0.27 mmHg (n = 4) was seen with 1.0 mg/kg of i.t. LTHC. In comparison, no significant IOP drop was apparent prior to 30 min with all doses (0.01-1.0 mg/kg) of i.p. LTHC tested, although a similar maximum drop in IOP (2.15 +/- 0.12 mmHg; n = 8) was obtained with 1.0 mg/kg of LTHC. The ED(50) for i.t. and i.p. LTHC was 0.08 mg/kg and 0.12 mg/kg, respectively. The IOP-lowering effects of i.p. LTHC (0.2 mg/kg) were reduced by 14% and 80% by 0.25 mg/kg (n = 6) and 2.5 mg/kg (n = 6), respectively, of the CB1R antagonist, SR141716A. In conclusion, i.t. LTHC was superior to i.p. LTHC in producing a more rapid and potent decrease in IOP. The IOP-lowering effect of LTHC was blocked by the CB1R-selective antagonist, SR141716A, suggesting that CB1Rs contribute to the ocular hypotensive effect of Delta9-tetrahydrocannabinol.
Szczesniak
Anna-Maria
AM
Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.
Kelly
Melanie E M
ME
Whynot
Sara
S
Shek
Pang N
PN
Hung
Orlando
O
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000008:administration & dosage*; D007429:Intraocular Pressure / Q000187:drug effects*; D008081:Liposomes; D051381:Rats; D011914:Rats, Inbred BN; D043884:Receptor, Cannabinoid, CB1 / Q000502:physiology
D000959:Antihypertensive Agents; D008081:Liposomes; D043884:Receptor, Cannabinoid, CB1; D013759:Dronabinol