There are two known endogenous cannabinoid receptors creatively named CB1 and CB2. CB1 receptors are found primarily but not exclusively in the brain. They are most prevalent in the hippocampus, cerebral cortex, basal ganglia, and cerebellum. CB2 receptors are also found in the brain but more so expressed by cells of the immune system, especially B cells. The CB receptor is a G protein mediated receptor that affects primarily calcium and potassium channel activation.
Functional changes are most notable in neuronal excitability and neurotransmitter release.
Initially, the receptors were considered orphaned receptors meaning that there were no endogenous ligands. Pharmacokinetics Marijuana is usually smoked but can be eaten or injected intravenously. Peak plasma levels are reached ten minutes after smoking. The psychoactive components are effective for two to three hours, however THC has a long half-life due to its lipid soluble nature and redistribution into fatty tissue. THC can be detected in urine months after initial administration.