Arvanil, anandamide and N-arachidonoyl-dopamine (NADA) inhibit emesis through cannabinoid CB1 and vanilloid TRPV1 receptors in the ferret

Luigia Cristino1, Lorraine D. Oland3, Marja D. Van Sickle3, Katarzyna Starowicz2, Q.J. Pittman3, Vittorio Guglielmotti1, Joseph S. Davison3, Vincenzo Di Marzo2, Keith A. Sharkey3. 1Endocannabinoid Research Group, Istituto di Cibernetica CNR, Pozzuoli, Naples, Italy, 2Endocannabinoid Research Group, Istituto di Chimica Biomolecolare CNR, Pozzuoli, Naples, Italy, 3Department of Physiology & Biophysics, University of Calgary, Calgary, Alberta, Canada.

Cannabinoid (CB) and transient receptor potential vanilloid-1 (TRPV1) receptor agonists are anti-emetic (Andrews et al., 2000; Hall et al., 2005). Anandamide (AEA) and N-arachidonoyl-dopamine (NADA) are endogenous agonists at both CB1 and TRPV1 receptors. Arvanil is a synthetic “hybrid” agonist of these receptors (Melck et al., 1999). URB597 is a specific inhibitor of fatty acid amide hydrolase, capable of elevating brainstem AEA levels. Previously, the anti-emetic effects of cannabinoids were proposed to be through the activation of cannabinoid CB1 or CB2 receptors expressed in nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus (DMNX) and area postrema (AP) (Van Sickle et al., 2003; 2005). With the purpose of assessing whether: i) AEA, NADA and arvanil inhibit emesis and related behaviours in a way mediated by both CB1 and TRPV1 receptors, and ii) CB1 and TRPV1 receptors are expressed at similar sites in the brainstem nuclei controlling emesis, pharmacological and immunohistochemical studies were performed in six adult male ferrets (Mustela putoris furo, 900-1500g) and three mice (Swiss, 60-70g). Antagonists (TRPV1: iodoresiniferatoxin, IRTX, 0.1 or 0.2 mg kg-1, or AMG9810 3 mg kg-1; CB1: AM251, 5 mg kg-1; CB2: AM630, 5 mg kg-1) were administered 15 min prior to other agents (vehicle: 2% DMSO, 1% Tween 80 in PBS; arvanil, 1 & 2 mg kg-1; NADA , 1 & 2 mg kg-1; AEA, 1 mg kg-1; URB597 5 mg kg-1) (all i.p.) and 15 min later the emetic agent, morphine 6 glucuronide (0.05 mg kg-1, s.c., M6G) was administered. The ferrets were observed for 1 hour to count the number of emetic episodes ( n ). Quantitative pharmacological data were compared using ANOVA followed by a Bonferroni post hoc test and showed significant (P<0.01) reduction of emesis episodes in response to M6G (n=7±0.2) for each administered compound (example: n=2.2±0.6 Arv2/M6G vs n=7.0±0.2 M6G); these effects were attenuated by both AM251 (n=4.8±0.4 vs n=2.2±0.6 Arv2/M6G), which was pro-emetic per se (n=9.0±0.5 vs n=7.0±0.2 M6G), and the TRPV1 antagonists IRTX (n=5.2±0.5 vs n=2.2±0.6 Arv2/M6G) and AMG9810, which were without pro-emetic effects per se. For immunohistochemical studies, ferret and mouse brainstem floating sections were processed for TRPV1-ir and TRPV1/CB1-ir. TRPV1-ir was largely restricted to the NTS and extensively co-localized with CB1-ir in the mouse. Our findings suggest that CB1 and TRPV1 receptors in the brainstem play a major role in the control of emesis by agonists of these two receptors. While there appears to be an endogenous “tone” of CB1 receptors inhibiting emesis, this does not seem to be the case for TRPV1 receptors, indicating that endocannabinoids/endovanilloids endogenously released following M6G administration inhibit emesis preferentially via CB receptors. However, pharmacologically elevated AEA levels inhibit emesis via both CB1 and TRPV1.

Andrews et al., 2000 Br J Pharmacol, 130, 1247-1254

Hall et al., 2005 Lancet Oncol, 6, 35-42;

Melck et al., 1999 Biochem Biophys Res Commun, 262, 275-84;

Van Sickle et al., 2003 Am J Physiol Gastroint Liver Phys, 285, 566-576

Van Sickle et al., 2005 Science, 310,329-332.