Amylin decreases meal size in rats

Adult male rats were intraperitoneally (IP) injected with 1.0 μg/kg amylin at the beginning of the dark phase in 24 h food deprived or undeprived rats, and a computerized system measured feeding behavior. In food deprived rats, amylin reduced the size of the first postdeprivation meal without affecting intrameal feeding rate or the size or timing of subsequent meals. The same pattern was observed in undeprived rats, but amylin also increased the latency to the first postinjection meal. In a conditioned taste aversion test, IP amylin (1 μg/kg) injection just prior to rats' first access to a saccharine-flavored version of their maintenance diet, failed to affect their subsequent selection of that diet relative to the maintenance diet 2 d later. Finally, 2-min meal-contingent hepatic portal infusions of amylin (1–3.2 μg/rat) during nocturnal spontaneous meals in undisturbed, ad lib fed rats reduced the meal size and meal duration, and increased the postprandial satiety ratio. Again, feeding rate and the size and duration of subsequent meals were not affected. These results suggest that amylin inhibits feeding by facilitating meal-ending satiety processes.