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Forebrain projections from cholecystokininlike‐immunoreactive neurons in the rat midbrain
Author(s) -
Seroogy Kim B.,
Fallon James H.
Publication year - 1989
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902790307
Subject(s) - olfactory tubercle , stria terminalis , ventral tegmental area , substantia nigra , nucleus accumbens , biology , midbrain , forebrain , pars compacta , tegmentum , neuroscience , anatomy , extended amygdala , ventral pallidum , medial forebrain bundle , striatum , amygdala , globus pallidus , dopamine , basal ganglia , central nervous system , dopaminergic
Abstract The purpose of the present study was to analyze the distribution of cholecystokininlike‐immunoreactive (CCK‐I) neurons within the rat ventral mesencephalon which project to several forebrain areas. The peroxidase‐antiperoxidase immunocytochemical technique was used to examine the anatomical localization of CCK‐I within the ventral midbrain and in the following forebrain regions: caudate‐putamen, nucleus accumbens, olfactory tubercle, bed nucleus of the stria terminalis, septum, amygdala, and prefrontal, anterior cingulate, and piriform cortices. CCK‐I perikarya were distributed throughout the substantia nigra, ventral tegmental area, and several midline raphe nuclei to a greater extent than previously reported, particularly in the substantia nigra pars compacta. Terminallike immunoreactivity for CCK was observed in all of the above forebrain sites. In addition, infrequent CCK‐I cell bodies were localized in the caudate‐putamen, nucleus accumbens, olfactory tubercle, septum, and bed nucleus of the stria terminalis. To analyze forebrain projections of the ventral midbrain CCK‐I neurons, indirect immunofluorescence was combined with fluorescence retrograde tracing. CCK‐I neurons of the substantia nigra and/or ventral tegmental area were found to project, to varying extents, to all of the above CCK‐I forebrain terminal fields. The nucleus accumbens, olfactory tubercle, and septal and prefrontal cortical projections arose primarily from CCK‐I perikarya in the ventral tegmental area whereas the projections to the caudateputamen and anterior cingulate cortex arose predominantly from immunoreactive neurons in the substantia nigra pars compacta. The amygdala received innervation mainly from CCK‐I cell bodies located in the substantia nigra pars lateralis. CCK‐I afferents to the bed nucleus of the stria terminalis and piriform cortex originated from perikarya distributed approximately equally across the ventral tegmental area and substantia nigra pars compacta. The general topography of CCK‐I forebrain innervation observed in this study is similar to that previously reported for the ascending dopaminergic projections from ventral mesencephalic neurons. CCK‐I neurons of the midline raphe nuclei were found to provide relatively minor afferents to the caudate‐putamen, bed nucleus of the stria terminalis, septum, and prefrontal cortex and more substantial projections to the amygdala. The results of this study demonstrate that CCK‐I neurons of the ventral midbrain supply a much broader innervation of forebrain regions than previously appreciated. Moreover, these data suggest that ventral mesencephalic CCK projections encompass the full range of the well‐known dopaminergic masolimbic. mesostriatal, and mesocortial projections. Thus, CCK may play a significant role in the ascending mesotelencephalic systems.