The ventral ('limbic-related) striatum mediates motivated behavior, and is considered an important anatomic Substrate of psychosis. The amygdala, a prominent limbic structure, links complex sensory stimuli to their emotional significance. One way the ventral striatum can be defined is based on inputs from structuresthat mediate emotional processing the amygdala; orbitomedial prefrontal regions linked to the amygdala, and the dorsal tier dopamine (DA) neurons. The ventral striatal 'shell' is a unique subregion that receives restricted inputs from these structures, and is charactenzed by 1. Relatively low calbindin-Dk28 (CaBP) staining, 2. Multiple cellular ('interface') islands with differential distributions of substance F, enkephalin, acetyicholinesterase (AchE), tyrosine hydroxylase (TH), and D1 mRNA, 3. Regions of precise overlap between amygdaloid afferents and cell clusters associated with specific transmitters, 4. Regions of tight overlap between amygdaloid and cortical afferents. We hypothesize that the caudoventral striatum and adjacent amygdalostriatal area (Astr) is a special part of the ventral 'limbic' striatum that is devoted to temporal lobe inputs, based on similar criteria. The temporal lobes mediate auditory and visual processing, are interconnected with the amygdala, and are a site of abnormalities in schizophrenia. Our preliminary data suggest that, like the ventral striatum, the caudoventral striatum/Astr area: 1. Receives afferents from brain structures mediating emotion: amygdala, specific regions of cortex linked to the amygdala, and the DA neurons. 2. Receives input from a caudal component of the 'dorsal tier' of DA neurons 3. Has a CaBP-poor region, and multiple cellular islands associated with varying distributions of substance F, enkephalin, AchE, TH, and D1 mRNA, similar to that found in the shell. The first goal of these studies is to determine whether the caudoventral striatum/Astr area is part of the ventral striatum based on connectional, cytoarchitectural, and histochemical features.
Our second aim i s to examine the hypothesis that the amygdala projects to cellular clusters containing substance P and Dl receptor mRNA in the caudoventral striatal/Astr area, and is therfore in a position to activate these transmitter/receptor specific pathways.
Our third aim i s to determine whether amygdaloid and temporal cortical inputs converge in the caudoventral striatum/Astr area. The results of these studies will provide an anatomic framework for understanding how emotionally significant auditory and visual information is processed in the striatum.
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