TEMPORAL LOBE PATHWAYS THROUGH THE DOPAMINE SYSTEM

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DESCRIPTION (provided by applicant): Structural abnormalities of the amygdala/hippocampal complex are a consistent finding in schizophrenia. In animal models, neonatal damage to the amygdala/hippocampal complex results in adult onset dopamine (DA) dysregulation, another key feature of this illness. Maintaining the integrity of amygdala/hippocampal circuits therefore appears critical to later DA function. We have previously shown that the extended amygdala, a major output region of the amygala and other temporal lobe structures, has broad inputs to the dopamine neurons. This pathway is thus a potential route by which amygdala-hippocampal abnormalities may eventually lead to DA dysregulation. The proposed studies will examine how the amygdala and hippocampus can influence the midbrain DA system through the extended amygdala. The fact that temporal lobe injury results in DA dysregulation only later in development suggests that plastic changes eventually influence DA output. Our preliminary results show that B lymphocyte 2 protein (bcl-2), which protects cells from excitotoxic damage and also has neurotrophic effects, is highly concentrated in specific subregions of the adult primate temporal lobe. Our preliminary results show high concentrations of Bcl-2 positive cells in the extended amygdala, and in subregions of the amygdala and hippocampus associated with schizophrenia. The presence of bcl-2 in specific circuits may help to identify excitatory pathways most susceptible to plastic changes and/or excitotoxic stress in adult animals. The proposed studies will identify temporal lobe circuits that influence DA through the extended amygdala. Specifically we will: 1) identify direct amygdaloid and hippocampal inputs to the extended amygdala-DA pathway, 2) identify indirect hippocampal pathways through the amygdala that influence the extended amygdala, 3) determine whether specific amygdaloid and hippocampal input/output paths contain Bcl-2 immunoreactive cells, 4) determine the extent to which hippocampal inputs overlap amygdala subregions that project to the extended amygdala, and the extent to which this input overlaps inhibitory interneurons and bcl-2-containing cells.