CB Receptors
The basics
Receptors interact with ligands in various ways. It is assumed that each receptor has an endogenous ligand, a chemical our body makes, but some receptors have only been identified due to an exogenous ligand. Exogenous ligands, chemical signals that originate from outside our bodies, can interact with receptors in various ways. Three main interactions include activation, inhibition, and modulation, although many complex interactions occur, notably with CBD.
The CB1 Receptor
The CB1 receptor was originally discovered in the search for THC’s mechanism of action. While it is expressed densely in the CNS, it is also found throughout the body. CB1 receptors are pivotal endocannabinoid system (ECS) components, playing crucial roles in numerous physiological processes. These receptors are part of a class of G-protein-coupled receptors, which are involved in transmitting chemical signals from the outside of a cell to the interior. The widespread distribution and diverse functions of CB1 receptors make them a subject of significant interest in both research and medicine.
CB1 receptors are expressed in many organ systems but are more densely populated in the central nervous system (CNS) than any other neurotransmitter receptor. This extensive presence underscores their critical role in regulating neurotransmission and various neural functions.
Beyond the CNS, CB1 receptors are found in peripheral organs and tissues, including the eyes, thyroid, heart, respiratory tract, gastrointestinal tract (stomach, intestines, pancreas), liver (including Kupffer cells), adipose tissue, bones, adrenal glands, connective tissues, and reproductive organs (ovaries, uterus, testes, and prostate).
Due to their extensive distribution and broad functional spectrum, CB1 receptors are a prime target for therapeutic interventions. They are involved in conditions ranging from chronic pain and epilepsy to anxiety, eating disorders, and neurodegenerative diseases. However, the therapeutic targeting of CB1 receptors must be approached with caution due to the potential for side effects, such as cognitive impairment, addiction, and mood changes.
The CB2 Receptor
The CB2 receptor is more expressed in peripheral tissues, mainly within immune cells and organs closely related to the lymphatic system.
CB2 receptors are integral to the endocannabinoid system (ECS) and are predominantly associated with modulating immune and inflammatory responses. Like CB1 receptors, CB2 receptors are G-protein-coupled receptors, but they are primarily expressed outside the central nervous system, especially in immune-related structures and the gastrointestinal (GI) system. Their role extends to various physiological functions, influencing everything from pain management to metabolic processes.
Given their role in regulating immune responses and inflammation, CB2 receptors have been identified as potential therapeutic targets for various diseases. In cardiovascular health, CB2 receptors can inhibit foam cell production, a critical step in developing atherosclerotic plaques. The presence of CB2 receptors in the brain, particularly in the context of inflammation and neuroprotection, suggests potential roles in treating neurodegenerative diseases like Alzheimer's and multiple sclerosis. There is growing interest in the role of CB2 receptors in cancer, particularly in how their activation might modulate immune responses and inhibit cancer cell proliferation.
