Effects of calcitonin injected into various brain areas on pain threshold and Ca2+ in rats
X. Zhao, S. Wang, and Y. Xia. Zhongguo yao li xue bao = Acta pharmacologica Sinica17 (3):
AIM: To study the effects of calcitonin (Cal) injected into different brain areas on pain threshold.
METHODS: The analgesic effects of Cal were investigated in rats by the tail-flick test.
RESULTS: Cal injected into lateral cerebral ventricle (LCV) or periaqueductal gray (PAG) increased obviously the pain threshold to 49 +/- 22\% or to 68 +/- 12\% (P \textless 0.01), respectively. When PAG was blocked with lidocaine, the analgesic effect of Cal injected into LCV was lowered 41 +/- 9\%. Cal injected into habenula (Hab) decreased the pain threshold to -30 +/- 5\% (P \textless 0.01).
CONCLUSION: Cal in different rat brain areas induced different effects on pain responses: analgesia or hyperalgesia, and showed that PAG played an important role in the analgesic effect induced by Cal, and the changing of pain threshold was mediated by the Ca2+ in brain.