A neural pathway mediating satiation of feeding behavior in Aplysia

This study investigated the pathway by which satiation is signaled to the central nervous system of Aplysia. In the first experiment, three groups of animals were studied: (1) animals with bilateral section of the cerebral-buccal (c-b) connectives, (2) sham-operated control animals, and (3) nonoperated control animals. Seaweed mash equivalent to a large meal was introduced via an esophageal cannula into the crops of all animals. Immediately after injection, 17 of the 18 animals in all three groups did not exhibit significant satiation, as measured by time to orient to food. However, on retesting 15 to 20 min later, the nonoperated controls and sham-operated controls were satiated, but the animals with sections of the cerebral-buccal connectives were not satiated. In a second experiment, it was found that injection of nonnutritive gel was sufficient to produce satiation of the orienting response. As in the first experiment, the satiation was not seen in the immediate test, but was seen 15–20 min later. The overall data suggest that gut mechanoreceptors may signal satiation by sending information that is conveyed via the cerebral-buccal connectives to the ganglia controlling food orientation. Furthermore, following stretch of the gut, satiation is seen only after a time delay.