Cannabinoids Biology: The Search for New Therapeutic Targets

Table 1^a.

Biological Characteristics of the CB₁ and CB₂ Receptors

	CB₁	CB₂
^a Adapted with permission from Sigma-RBI Handbook of Receptor Classification and Signal Transduction.
Size (amino acid residues)	472	360
Tissue expression	Brain (cerebellum, basal ganglia, cerebral cortex), liver, testes	Peripheral immune cells, sparse in brain
Physiological function	Presynaptic heteroreceptor; inhibits neurotransmitter release	Suppress immune cell function
Disease relevance	Pain, appetite regulation, anxiety, craving, emesis	Pain, immune system regulation, muscle spasms
Signal transduction mechanisms	Gα_i (cAMP modulation)  Inhibits voltage-sensitive Ca²⁺ channels (N-, Q-type)  Activates K_ir and K_A conductance	Gα_i (cAMP modulation)
Endogenous agonists (common to both CB₁ and CB₂)	Arachidonoyl ethanolamide (anandamide)
	2-Arachidonoyl glycerol (2-AG)
	2-Arachidonoyl glyceryl ether (Nolandin ether)
	N-Arachidonoyl dopamine
	O-Arachidonoyl ethanolamine (Virodhamine)