The effect of experimental epilepsy induced by injection of tetanus toxin into the amygdala of the rat on eating behaviour and response to novelty

A minute dose of tetanus toxin injected into the amygdala of rats produced an apparently reversible epileptiform syndrome similar to that previously d escribed after injection of the toxin into the hippocampus. During the acti ve epilepsy the toxin-injected rats occasionally exhibited 'paroxysmal eati ng' and also sometimes ran round in circles attempting to bite their own ta ils. When presented with a novel but palatable food (chocolate buttons or h arvest crunch) the toxin-injected rats showed less neophobia than their con trols-they ate sooner and ate more. This was found both during the active e pilepsy and several weeks later when they had recovered. A similar effect o f amygdala injections was found in a second experiment, in which the effect was compared with that of toxin injection in the hippocampus. These rats w ere tested also on the playground maze on their approach response to a neut ral novel object (in a familiar environment in the context of seven familia r objects). The amygdala rats did not show any increase in their novelty re sponse; thus their reduction in neophobia was specific to an appetitive beh aviour. In contrast, the hippocampally-injected rats did not exhibit a nove lty response in the playground maze, but showed normal neophobia to a new f ood. (C) 1999 Elsevier Science B.V. All rights reserved.