Terpenes in Cannabis sativa Inhibit Capsaicin Responses in Rat DRG Neurons via Na+/K+ ATPase Activation

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“Terpenes in Cannabis sativa exert analgesic effects, but the mechanisms are uncertain. We examined the effects of 10 terpenes on capsaicin responses in an established model of neuronal hypersensitivity. Adult rat DRG neurons cultured with neurotrophic factors NGF and GDNF were loaded with Fura2AM for calcium imaging, and treated with individual terpenes or vehicle for 5 min, followed by 1 µMol capsaicin. In vehicle treated control experiments, capsaicin elicited immediate and sustained calcium influx. Most neurons treated with terpenes responded to capsaicin after 6-8 min. Few neurons showed immediate capsaicin responses that were transient or normal. The delayed responses were found to be due to calcium released from the endoplasmic reticulum, as they were maintained in calcium/magnesium free media, but not after thapsigargin pre-treatment. Terpene inhibition of calcium influx was reversed after washout of medium, in the absence of terpenes, and in the presence of the Na+/K+ ATPase inhibitor ouabain, but not CB1 or CB2 receptor antagonists. Thus, terpenes inhibit capsaicin evoked calcium influx by Na+/K+ ATPase activation. Immunofluorescence showed TRPV1 co-expression with α1β1 Na+/K+ ATPase in most neurons while others were either TRPV1 or α1β1 Na+/K+ ATPase positive.”


“The neuromodulatory effects of cannabinoids have been recognized for millenia in traditional medicine, including for pain relief. Following the opioid crisis, attention has been focussed on developing alternatives including cannabinoid-based pain therapies, as chronic pain remains an unmet need. The best known of the phytocannabinoids is Δ9tetrahydrocannabinol (THC), the only known psychoactive component, along with many other cannabinoids with potential therapeutic benefits, such as cannabidiol (CBD), and cannabigerol (CBG) [2]. Amongst the several hundred components in Cannabis sativa are terpenes, which are produced in small and varying amounts in different cultivars of C. sativa, leading to potential variation in their effects [3]. Some of these, including limonene, phytol, borneol, terpineol, and caryophyllene, provide pain relief via calcium channel inhibition [4]. Similarly, antinociceptive and anti-tumour effects of α-phellandrene were reported, although the mechanisms were unknown. Terpenes as a class of compounds are generally described as safe by the FDA, with low toxicity that extends their efficacy to a variety of indications including chronic pain and anxiety.”


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