Contrasting role of octopamine in appetitive and aversive learning in the crab Chasmagnathus

KACZER LAURA; HECTOR MALDONADO

Congreso; Primera Reunión conjunta de Neurociencias; 2009

Octopamine (OA) is considered the invertebrate counterpart of noradrenaline and several studies in insects converge on the idea that OA mediates the reward in appetitive conditioning. However, it is possible to assume that OA could have a different role in an aversive conditioning.We pharmacologically studied the participation of OA in two learning processes in the crab Chasmagnathus granulatus, one appetitive and one aversive. Our results demonstrate that the role of OA is divergent in these two types of learning. It is shown that the aversive memory is impaired by an OA injection applied immediately or 30 minutes after the last training trial. By contrast, the appetitive memory is blocked by OA antagonists epinastine and mianserine, but enhanced by OA when injected together with the supply of a minimum amount of reinforcement. Finally, double-learning experiments in which crabs are given the aversive and the appetitive learning either successively or simultaneously, allow us to study the interaction between both types of learning and analyze the presumed action of OA. We found that the appetitive training offered immediately, but not one hour after an aversive training, has an amnesic effect on the aversive memory that mimics the effect and the kinetic of an OA injection.These findings lead to a novel scenario of OA action in learning and memory, showing that it would act differently in memory processes of opposite signs.