EFFECTS OF CALCITONIN INJECTED INTO VARIOUS BRAIN-AREAS ON PAIN THRESHOLD AND CA2+ IN RATS

AIM: To study the effects of calcitonin (Gal) injected into different brain areas on pain threshold. METHODS: The analgesic effects of Cal w ere investigated in rats by the tail-flick test. RESULTS: Cal injected into lateral cerebral ventricle (LCV) or periaqueductal gray (FAG) in creased obviously the pain threshold to 49 +/- 22 % or to 68 +/- 12 % (P<0.01), respectively. When FAG was blocked with lidocaine, the analg esic effect of Cai injected into LCV was lowered 41 +/- 9 %. Cal injec ted into habenula (Hab) decreased the pain threshold to - 30 +/- 5 % ( P < 0.01). CONCLUSION: Cat in different rat brain areas induced differ ent effects on pain responses: analgesia or hyperalgesia, and showed t hat FAG played an important role in the analgesic effect induced by Ga l, and the changing of pain threshold was mediated by the Ca2+ in brai n.