PT  - JOURNAL ARTICLE
AU  - Saoirse E. O'Sullivan
AU  - Michael D. Randall
AU  - Sheila M. Gardiner
TI  - The in Vitro and in Vivo Cardiovascular Effects of Δ<sup>9</sup>-Tetrahydrocannabinol in Rats Made Hypertensive by Chronic Inhibition of Nitric-Oxide Synthase
AID  - 10.1124/jpet.106.116566
DP  - 2007 May 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 663--672
VI  - 321
IP  - 2
4099  - http://jpet.aspetjournals.org/content/321/2/663.short
4100  - http://jpet.aspetjournals.org/content/321/2/663.full
SO  - J Pharmacol Exp Ther2007 May 01; 321
AB  - Evidence suggests that Δ9-tetrahydrocannabinol (THC) may have antihypertensive effects and that the vasodilator effect of endocannabinoids is enhanced in rats made hypertensive by chronic NO synthase inhibition. Therefore, the aims of the present study were to investigate whether the in vitro and in vivo cardiovascular responses to THC are altered by Nω-nitro-l-arginine methyl ester (l-NAME) treatment. The vasorelaxant effects of THC were enhanced in small mesenteric arteries from l-NAME-treated rats. This enhanced response was not inhibited by cannabinoid CB1 receptor antagonism [1 μM N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide; AM251]. Pretreating vessels with the transient receptor potential vanilloid receptor receptor agonist capsaicin at 10 μM for 1 h reduced vasorelaxation to THC to a greater extent in l-NAME-treated than control rats. Inhibition of cyclooxygenase with 10 μM indomethacin inhibited THC responses in arteries from l-NAME-treated rats but not from control rats. In conscious, chronically instrumented rats, 1 mg kg–1 i.v. THC caused a pressor effect, with vasoconstriction of the renal and mesenteric vascular beds, and hindquarters vasodilatation. Pretreatment with 3 mg kg–1 i.v. AM251 reduced the pressor and vasoconstrictor effects of THC, abolished the hindquarters vasodilatation, and revealed a bradycardic response. l-NAME-treated rats showed similar pressor and vasoconstrictor responses to THC, but with bradycardia, and reduced hindquarter vasodilatation. These data show that, in vitro, isolated arteries of l-NAME-treated rats show enhanced vasorelaxant responses to THC through an increased sensory nerve component and stimulation of prostanoids. However, in vivo, THC causes a CB1 receptor-mediated pressor effect with hindquarters vasodilatation. There was no evidence of enhanced vasodilator effects of THC in l-NAME-treated animals in vivo. The American Society for Pharmacology and Experimental Therapeutics