Absence of Entourage: Terpenoids Commonly Found in Cannabis sativa Do Not Modulate the Functional Activity of Δ(9)-THC at Human CB(1) and CB(2) Receptors

Introduction: Compounds present in Cannabis sativa such as phytocannabinoids and terpenoids may act in concert to elicit therapeutic effects. Cannabinoids such as Δ(9)-tetrahydrocannabinol (Δ(9)-THC) directly activate cannabinoid receptor 1 (CB(1)) and cannabinoid receptor 2 (CB(2)); however, it is not known if terpenoids present in Cannabis also affect cannabinoid receptor signaling. Therefore, we examined six common terpenoids alone, and in combination with cannabinoid receptor agonists, on CB(1) and CB(2) signaling in vitro. Materials and Methods: Potassium channel activity in AtT20 FlpIn cells transfected with human CB(1) or CB(2) receptors was measured in real time using FLIPR(®) membrane potential dye in a FlexStation 3 plate reader. Terpenoids were tested individually and in combination for periods up to 30 min. Endogenous somatostatin receptors served as a control for direct effects of drugs on potassium channels. Results: α-Pinene, β-pinene, β-caryophyllene, linalool, limonene, and β-myrcene (up to 30–100 μM) did not change membrane potential in AtT20 cells expressing CB(1) or CB(2), or affect the response to a maximally effective concentration of the synthetic cannabinoid CP55,940. The presence of individual or a combination of terpenoids did not affect the hyperpolarization produced by Δ(9)-THC (10 μM): (CB(1): control, 59%±7%; with terpenoids (10 μM each) 55%±4%; CB(2): Δ(9)-THC 16%±5%, with terpenoids (10 μM each) 17%±4%). To investigate possible effect on desensitization of CB(1) responses, all six terpenoids were added together with Δ(9)-THC and signaling measured continuously over 30 min. Terpenoids did not affect desensitization, after 30 min the control hyperpolarization recovered by 63%±6% in the presence of the terpenoids recovery was 61%±5%. Discussion: None of the six of the most common terpenoids in Cannabis directly activated CB(1) or CB(2), or modulated the signaling of the phytocannabinoid agonist Δ(9)-THC. These results suggest that if a phytocannabinoid–terpenoid entourage effect exists, it is not at the CB(1) or CB(2) receptor level. It remains possible that terpenoids activate CB(1) and CB(2) signaling pathways that do not involve potassium channels; however, it seems more likely that they may act at different molecular target(s) in the neuronal circuits important for the behavioral effect of Cannabis.