Effects of calcitonin, parathyroid hormone and its related fragments on acquisition of active avoidance behavior

The acquisition of active avoidance response was studied in rats injected intracerebroventricularly with calcitonin (CT), parathyroid hormone (PTH) or PTH-related fragments. PTH and PTH65-84 facilitated the acquisition of shuttle-box active avoidance behavior as indicated by the number of conditioned avoidance responses and the percentage of animals reaching the learning criterion. PTH1-34 and PTH44-68, on the contrary, inhibited the acquisition of active avoidance behavior, while CT totally suppressed this behavior in the rat. It is possible that the opposite effects of PTH and CT on learning ability of the rat depend on a different action on calcium metabolism.