The Influence of the Concentration of Receptors With Affinity for Cannabidol and Cannabinol on the Risk of Occurrence and Severity of Chronic Orofacial Pain of Muscle Origin

Background: Orofacial pain is a common phenomenon in adult patients in Poland. According to available scientific research, it occurs in over half of the population, i.e. 55.9% In its chronic form, orofacial pain may lead to reduced sleep quality, reduced life satisfaction and psychoemotional disorders, including depressive disorders. A popular trend among patients suffering from chronic orofacial pain is the abuse of non-steroidal anti-inflammatory drugs, which in most cases demonstrate low, short-term effectiveness and disproportionate to the side effects. There are scientific reports suggesting that substances such as cannabidol (CBD) and cannabinol (CBN) may be effective in the treatment of chronic nociceptive and neuropathic pain, but there is a clear lack of research on the importance of the concentration of receptors on which they can potentially affect exogenous cannabinoids in the risk of occurrence and development of chronic pain. Of the many receptors to which cannabinoids have affinity, the present study selected those that are involved in neurotransmission related to pain, in particular orofacial pain. The concentrations of CB1, CB2, TRPV-1 receptors will be examined, below is a brief description of each of them to explain their selection.

CB1 and CB2 receptors are G protein-coupled metabotropic receptors and belong to the 7-transmembrane receptor family. CB1 has been detected in central nervous system synapses and sensory neurons. The effect of high CB1 expression in areas closely related to the regulation of pain sensation is the relief of migraine and neuropathic pain. However, CB2 receptors can be found in T and B lymphocytes, spleen, pancreas and tonsils. They work to modulate the release of cytokines and the migration of immune cells in a way that appears to reduce inflammation and some types of pain.

The TRPV-1 receptor is the so-called transient potential 1 vanilloid receptor. They occur primarily at the peripheral endings of nerve fibers, where, as a result of the stimuli that stimulate them, they may participate in the development and conduction of pain. The receptor mediates peripheral pain sensation, able to lower the activation threshold and delay the response of nociceptors. Secondary analgesia following ligand-dependent activation is used in the treatment of some difficult-to-control types of pain, e.g. neuropathic pain. TRPV1 can be activated by endogenous substances, e.g. anandamide, or exogenous substances, e.g. cannabinoids contained in cannabis. It is also worth adding that CBD has the property of blocking FAAH (the enzyme fatty acid amide hydrolase), protecting anandamide against degradation, which means that CBD is also an agonist towards TRPV-1 and protects the natural agonist against degradation by FAAH.

Aim: The aim of this study is to answer how the concentration of the above receptors may influence the occurrence of chronic pain in the masticatory muscles in the study population.

It should be mentioned that CB1, CB2 and TRPV-1 receptors have not yet been included in this research perspective and there are no publications or scientific reports on this subject.