THE ANTI-APOPTOSIS BCL-2 PROTOONCOGENE IS PREFERENTIALLY EXPRESSED INLIMBIC STRUCTURES OF THE PRIMATE BRAIN

By virtue of its capacity to prevent apoptosis the protooncogene bcl-2 is believed to play a crucial role in CNS development, Studies in rod ents have shown that the anti-apoptosis Bcl-2 protein is widely expres sed during CNS development, but undergoes a marked down-regulation dur ing maturation and is present only at low concentrations in adult CNS. In contrast, current data suggest that Bcl-2 protein in adult monkey brain results from microglial expression, In the present immunohistoch emical study, however, numerous subsets of Bcl-2-immunoreactive neuron s were encountered in the amygdala, hippocampus, hypothalamus, limbic cortices and striatum of squirrel monkeys, Of particular interest was the presence in the basal portion of the amygdala and adjoining pirifo rm cortex of numerous intensely immunoreactive cells with long and thi ck immunopositive processes that ran into the ventral amygdalofugal pa thway, At striatal level Bcl-2-positive neurons were strictly confined to calbindin-poor striosomes, which are specifically innervated by li mbic cortices, This study has provided the first evidence for the occu rrence of Bcl-2 in mature monkey brain, It has further shown that this protein is preferentially expressed in limbic structures in primate f orebrain, The sustained expression of this anti-apoptosis protein may protect limbic system neurons from various injuries or neurodegenerati on. It may also be involved in the functional and structural changes t hat occur throughout adulthood in some regions of the primate limbic s ystem. (C) 1997 IBRO. Published by Elsevier Science Ltd.