How do cannabinoids modulate pain sensation? In other words, describe the mechanism of action of cannabinoids.
Endocannabinoids are synthesized in the postsynaptic neuron in response to stimuli such as pain, stress and inflammation. Endocannabinoids travel in a retrograde fashion and activate the presynaptic CB receptors. Antinociceptive effects occur when either endocannabinoids or phytocannabinoids activate presynaptic inhibitory CB1 receptors. Stimulation of CB1 receptors (G protein coupled receptors (Gi,Go)) leads to a reduction of cAMP production via the inhibition of adenylyl cyclase. This results in an action on voltage gated calcium and potassium channels – there is a depression of neuronal excitability and a reduction of neurotransmitter release.