[Abstract Title]. - Society for Neuroscience

Topic: D.08.n. Visceral pain
Title: Assessment of naturally occurring cannabinoids in response to visceral pain
Authors: *L. BOOKER, A. LICHTMAN;
Pharmacol., Virginia Commonwealth Univ., Richmond, VA
Abstract: Considerable attention has been focused on examining the antinociceptive effects of
Γ 9 -tetrahydrocannabinol (Γ 9 -THC), the major psychoactive constituent of Cannabis sativa. In
addition to Γ 9 -THC, there are approximately 70 cannabinoids present in cannabis. The primary
purpose of this study was to determine the analgesic effects of prevalent phytocannabinoids,
which include Γ 9 -THC, cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC), and
Γ 8 -tetrahydrocannabivarin (THCV), in the acetic acid stretching test, a visceral pain model. Γ 9 -
THC (ED50 = 0.32 mg/kg) and CBN produced analgesic effects, though CBN was only effective
at 50 mg/kg. The CB1 receptor antagonist, rimonabant, but not the CB2 receptor antagonist,
SR144528, blocked the analgesic effects of both compounds. Conversely, CBD and CBN failed
to decrease stretching. While THCV alone failed to affect acetic acid-induced stretching, it
displayed antagonistic properties when co-administered with Γ 9 -THC. Because the CB2 receptor
has been associated with inflammatory states in the GI tract, we examined whether
administration of a CB2 receptor agonist, O-3223, would elicit analgesic effects in the acetic acid
stretching test. Although O-3223 was without apparent activity, a selective CB1 receptor agonist
arachiodonyl 2‟-chloroethylamide produced antinociception. All compounds having an analgesic
effect did so at doses that did not reduce spontaneous locomotor activity, arguing against
impaired motor function as a confounding variable. These data indicate that Γ 9 -THC and CBN
reduce nociception in the acetic-acid stretching test through a CB1 receptor mediated mechanism.
Moreover, the observation that THCV blocked the antinociceptive effects of Γ 9 -THC raises the
possibility that phytocannabinoids present in marijuana interact to influence antinociception.
Disclosures: L. Booker , None; A. Lichtman, None.
Poster
269. Pain: Visceral Pain II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 269.10/GG25
Topic: D.08.n. Visceral pain
Support: NIH Grant HL75524