Behavioral effects pain modulation

A9-Tfetrahydrocannabinol (A9-THC), the psychoactive constituent of Cannabis binds to a specific G-protein coupled receptor in the brain. Although the cannabinoid receptor in the rat and in the human has been cloned, its physiological function is unknown. The well established behavioral effects of THC and the abundance and anatomical localization of the receptor in the brain suggest a role for the receptor in the control of movement, memory, emotions and pain modulation, amongst other activities. 

Within the past few years, it has become recognized that the immune system communicates to the brain. Substances released from activated immune cells ( cytokines") stimulate peripheral nerves, thereby signaling the brain and spinal cord that infection/ inflammation has occurred. Additionally, peripheral infection/inflammation leads to de novo synthesis and release of cytokines within the brain and spinal cord. Thus, cytokines effect neural activation both peripherally and centrally. Through this communication pathway, cytokines such as interleukin-1, interleukin-6 and tumor necrosis factor markedly alter brain function, physiology and behavior. One important but underrecognized aspect of this communication is the dramatic impact that immune activation has on pain modulation. 

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