FEAR DECREASE IN TRANSGENIC MICE OVEREXPRESSING BCL-2 IN NEURONS

NEURONAL destruction in the amygdala, hypothalamus and cerebellum prov okes a diminution in anxiety and neophobia. In transgenic mice that ex press the human bcl-2 gene under the control of neuron specific enolas e promotor (Hu-bcl-2), BCL-2 overexpression reduces the naturally occu rring neuronal death, producing an increase of the number of neurons a nd brain size. Since BCL-2 over-expression has been observed in differ ent parts of the brain and especially in the amygdaloid nuclei, the hy pothalamus and the cerebellum, we studied the fear-related behavior of these transgenic mice. Hu-bcl-2 transgenic mice showed a decrease in anxiety and neophobia, indicating that, for this particular behavior, supernumerary neurons elicit the same modification as that observed af ter neuronal destruction.