The effects of amylin on motivated behavior in rats

The effects of administration of amylin into the lateral brain ventricle on active and passive avoidance behavior and open field activity were studied in rats. Amylin increased the latency of passive avoidance behavior in a dose-dependent manner between 250 ng and 1 microgram, but 50 and 100 ng and 2 micrograms were ineffective when given immediately after passive avoidance conditioning. As concerns active avoidance behavior, the extinction was facilitated in a dose-dependent manner. The locomotion in an open field was inhibited at 3 h at 500 ng and 1 microgram doses and at 6 h at 250 and 500 ng and 1 microgram doses. However, the action was still present 24 h after administration of a large dose (1 microgram). The rearing activity was increased 3 and 6 h after administration of 1 microgram. Smaller doses (50, 100, 250, and 500 ng) were ineffective. Twenty-four hours following administration, none of the doses used exhibited any effect. The grooming activity was increased 3, 6, and 24 h after administration of 1 microgram amylin. Other doses were ineffective. The results suggest that amylin influences the behavioral reaction in these paradigms mainly by acting on locomotion, and not by modifying learning and memory processes.