Cannabidiol and terpenoid interactions in amygdalar regulation of pain states

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PROJECT SUMMARY Chronic pain affects up to one third of the United States population, and the reliance on opioids to treat chronic pain has contributed substantially to the opioid epidemic. Developing alternative pain therapies is critical to reducing the use of opioids, and the phyto-cannabinoid cannabidiol (CBD) is a promising candidate. We have shown that CBD has the ability to reduce chronic neuropathic pain-like responses in mice over 3 weeks. Terpenoids (eg beta-caryophyllene), also found in the cannabis plant, are a potential second class of pharmacologically active compounds in cannabis with possible analgesic benefits, although their pharmacodynamic properties in vitro and in vivo are poorly understood. Likewise, there is an incomplete understanding of how CBD and terpenoids produce anti-nociception, by themselves or combined (“entourage”), and their supraspinal neuropharmacological mechanisms of “pain control” remain unknown. The proposed experiments will first test whether specific combinations of CBD and terpenoids can produce short-term inflammatory and long-term neuropathic antinociception without tolerance. We will then establish the action of CBD and terpenoids in a critical brain nucleus for pain, the basolateral amygdala. Finally, we will determine the pharmacological and biochemical signaling profiles of CBD and terpenoids in vitro and in vivo. In Aim 1, we will use mixtures of CBD and terpenoids, investigator administered as well as in our gelatin self-administration model, and measure both consumption and pain scores after partial sciatic nerve ligation to determine if CBD and/or terpenoids provide analgesic benefit over protracted periods of pain. We will also verify that these mixtures are not inherently rewarding, which is critical for substance abuse liability. In Aim 2, we will test whether the amygdala is a critical brain circuit site for CBD/terpenoid analgesic action using single cell calcium imaging of amygdalar neurons during pain states, in parallel with local injections of CBD and terpenoids into the amygdala to produce analgesia. Further, we will knock out cannabinoid receptors and other putative sites of CBD/terpenoid action within the BLA to establish necessity of each in producing behavioral and physiological responses. In Aim 3, we will use in vitro and in vivo systems to determine the important biochemical features of CBD and terpenoid action at their putative receptor targets. We will measure cellular signaling activity via dynamic mass redistribution (DMR), MAP Kinase signaling, and the generation of reactive oxygen species. These aims will inform public health about the benefits and risks of long-term cannabidiol/terpenoid usage, as well as providing crucial mechanistic insight that will help develop and understand whether tailored medicinal cannabis approaches for chronic pain can be harnessed for therapeutic benefit.