Mu-opioid receptor–Cannabinoid receptor 1 system (MOR–CB1)

The Mu-opioid receptor–Cannabinoid receptor 1 (MOR–CB1) receptor system is a functional complex formed by the physical association, or heteromerization, of the Mu-opioid receptor and the Cannabinoid receptor 1 (Rios et al., 2006; Hojo et al., 2008). This system is predominantly located in the central nervous system, with high density in regions such as the nucleus accumbens, striatum, and the dorsal horn of the spinal cord, where it plays a critical role in modulating pain, reward, and energy homeostasis (Taskan et al., 2021; Zhang et al., 2020). Heteromerization confers unique pharmacological properties to the complex, including reciprocal allosteric modulation and altered receptor trafficking that differ from the individual receptors (Rios et al., 2006). Consequently, the MOR–CB1 system is a significant therapeutic target for the treatment of chronic pain and substance use disorders, as targeting the heteromer may enhance analgesic potency while reducing the risk of opioid-related side effects like tolerance and addiction (Zhang et al., 2020). Research into bivalent ligands that simultaneously engage both receptor sites is currently a major focus for developing safer and more effective pain management strategies (Zheng et al., 2013; Le Naour et al., 2013).

Other names

MOR-CB1 heteromerMu-opioid receptor-Cannabinoid receptor 1 complexMOP-CB1 heteromerMOR-CB1R heteromer

The MOR–CB1 receptor system operates through the physical heteromerization of the Mu-opioid receptor and Cannabinoid receptor 1, which facilitates reciprocal allosteric modulation and negative crosstalk between the two protomers. This interaction modifies G-protein coupling and downstream signaling pathways, such as the inhibition of adenylyl cyclase and the activation of mitogen-activated protein kinases (MAPK), leading to altered physiological responses in pain and reward circuits compared to the individual receptors.