Mind and body medicine: acupuncture
Acupuncture reduced stress-related behavior (from maternal separation in rats) and normalized HPA-induced corticosterone release [221]. Electroacupunture (EA) reduced thermal hyperalgesia and mechanical allodynia induced by an injection of complete Freund's adjuvant into rat paws. EA increased AEA levels in skin tissue. The antinociceptive effects of EA were attenuated by the CB2 antagonist AM630, but not by the CB1 antagonist AM251 [222]. Moreover, EA upregulated the expression of CB2 receptors in skin tissues [223]. It appears likely that CB2 activation in the skin stimulates the release of β-endorphin, which then acts on peripheral μ-opioid receptors to inhibit nociception [224].
However, CB1 may play a role in the central effects of EA: rats treated with EA showed reduced GABA levels in the ventrolateral periaqueductal gray, an effect reversed by CB1 blockade with AM251 [225]. Enhanced activation of epsilon protein kinase C in rat brain by EA was reversed by CB1 blockade with AM251 and not by CB2 blockade with AM630 [226].