Mechanism of Action
CB1 receptors are coupled through Gi/o proteins and inhibit adenylyl cyclase and activate mitogen-activated protein (MAP) kinase. In addition, CB1 receptors inhibit presynaptic N- and P/Q-type calcium channels and activate inwardly rectifying potassium channels. CB1 antagonists produce inverse cannabimimetic effects that are opposite in direction from those produced by agonists for these receptors.
CB1 receptors are highly expressed in hypothalamic areas which are involved in central food intake control and feeding behavior. This strongly indicates that the cannabinoid system is directly involved in feeding regulation. These regions are also interconnected with the mesolimbic dopamine pathway, the so-called "reward" system. Therefore, CB1 antagonists might indirectly inhibit the dopamine-mediated rewarding properties of food. Peripheral CB1 receptors are located in the gastrointestinal (GI) tract, liver and in adipose tissue. In the GI, CB1 receptors are located on nerve terminals in the intestines. Endocannabinoids act at the CB1 receptors to increase hunger and promote feeding and it is speculated that they decrease intestinal peristalsis and gastric emptying. Thus, antagonism at these receptors can inverse these effects. Also, in peripheral tissues, antagonism of CB1 receptors increases insulin sensitivity and oxidation of fatty acids in muscles and the liver. A hypothetical scheme for the metabolic effects of CB1 receptor antagonists is shown in Figure 1.
Read more about this topic: Cannabinoid Receptor Antagonist
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