In Defense of the “Entourage Effect”: Terpenes Found in Cannabis sativa Activate the Cannabinoid Receptor 1 In Vivo
Authors: LaVigne Justin , Hecksel Ryan , Streicher John M. 
Published: April 2020

Cannabis sativa, or marijuana, is the most commonly used illicit drug in the United States. Recreational and medical use has increased over the past decade due to loosening laws and legalization in 11 states. Anecdotal evidence from users suggests the therapeutic value of C. sativa is greater when the whole plant is consumed versus individual constituents such as D9‐tetrahydrocannabinol (D9‐THC). This observation has been termed the “entourage effect” and is hypothesized to derive from the combinatorial effect of phytocannabinoids and terpenes; the sum of the constituents found in the whole plant. C. sativa varieties contain ~150 phytocannabinoids and over 100 terpenoids. Prevalent monoterpenes include a‐pinene, linalool, limonene, and b‐myrcene, while prevalent sesquiterpenes include b‐caryophyllene (a known cannabinoid receptor 2 (CB2) agonist) and a‐humulene. These terpenoid compounds dictate the specific aromas and flavors of cannabis. Although terpenes can be lost during heat extractions, cold extraction using CO2 can increase terpene content upwards of 10‐fold. With increased terpene concentrations, a stronger case for the “entourage effect” can be made. Recent evidence has been published against the “entourage effect”, however, terpenes in these studies were used at very low doses or were studied in a single in vitro model. We sought to test the question: is the “entourage effect” a possible physiological phenomenon? We thus tested individual terpenes of C. sativa for cannabinoid receptor 1 (CB1R) activity in comparison with the synthetic cannabinoid WIN55,212. Four terpenes, varying in amounts in C. sativa, were chosen for screening: linalool and a‐humulene (med‐high), b‐pinene (low‐med), and geraniol (low). Preliminary in vitro results demonstrated that each of these terpenes were agonists at the CB1R. In mice, activation of CB1Rs by CB1 agonists induces four distinct physiological responses known as the CB1R tetrad: antinociception, hypolocomotion, catalepsy, and hypothermia. Each terpene was subsequently tested for activity in the tetrad. Intraperitoneal injection (£ 200 mg/kg) of a‐humulene, b‐pinene, and geraniol resulted in a dose‐dependent increase in tail flick thermal latency, an indication of antinociception; linalool had no effect. Interestingly, at 200 mg/kg a‐humulene, b‐pinene, and geraniol were able to induce an effect greater than or equivalent to 5.6 mg/kg WIN55,212. These effects were at least partially mediated by the CB1R, as 3 mg/kg rimonabant (CB1R antagonist) caused partial reversal. At 200 mg/kg, each terpene caused a significant decrease in hypolocomotion, an increase in catalepsy, and decrease in core temperature. These preliminary results suggest these terpenes may induce CB1R‐dependent behaviors in mice, thus promoting the possibly of an “entourage effect”. Ongoing studies are examining the interaction between known CB1R ligands and these terpenes to identify whether their interactions at the CB1R are competitive or allosteric in nature, and whether these ligands interact behaviorally.Support or Funding InformationThis study was supported by institutional funds from the University of Arizona. JMS has received research funding from Botanical Results, LLC (not related to current study).