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Ventral mesencephalic neurons containing both cholecystokinin‐ and tyrosine hydroxylase‐like immunoreactivities project to forebrain regions
Author(s) -
Seroogy Kim B.,
Dangaran Karol,
Lim Steven,
Haycock John W.,
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.902790306
Subject(s) - ventral tegmental area , substantia nigra , tegmentum , biology , pars compacta , tyrosine hydroxylase , nucleus accumbens , ventral pallidum , olfactory tubercle , midbrain , pars reticulata , retrograde tracing , cholecystokinin , basal forebrain , neuroscience , dopamine , anatomy , basal ganglia , nucleus , globus pallidus , central nervous system , dopaminergic , biochemistry , receptor
The coexistence of cholecystokinin‐ and tyrosine hydroxylase‐like immunoreactivities within neurons of the rat ventral mesencephalon was analyzed by using an indirect immunofluorescence technique for the simultaneous demonstration of two antigens in the same tissue section. A high degree of colocalization was observed in the substantia nigra pars compacta, in which 80–90% of all labeled neurons at rostral and up to 70% at intermediate levels contained both cholecystokinin and tyrosine hydroxylase. At caudal levels, the incidence of colocalization declined to approximately 30–50%. All of the immunoreactive perikarya in the substantia nigra pars lateralis were labeled with both substances. Other areas of the ventral midbrain that exhibited a moderate proportion of neurons immunoreactive for both cholecystokinin and tyrosine hydroxylase included the ventral tegmental area, interfascicular nucleus, and rostral and caudal linear nuclei. In addition, coexistence was occasionally observed within neurons of the central and ventral periaqueductal gray matter, supramammillary region, peripeduncular region, retrorubral field, and, extremely rarely, within the substantia nigra pars reticulata. Cell bodies containing tyrosine hydroxylase‐like immunoreactivity (indicative of dopamine) usually outnumbered those containing the peptide except in the supramammillary region and in the ventral periaqueductal gray matter, where the cholecystokinin perikarya were present in higher numbers. The double‐labeling colocalization technique was combined with fluorescence retrograde tracing to determine some of the forebrain projections of these neurons. Ventral midbrain neurons containing both cholecystokinin and tyrosine hydroxylase were found to project to the caudate‐putamen, nucleus accumbens, prefrontal cortex, and amygdala. These projections originated from neurons located predominantly in the substantia nigra pars compacta and the ventral tegmental area. Thus, cholecystokinin occurs within the well‐known dopaminergic nigrostriatal pathway in the rat. Overall, these results demonstrate that a significant proportion of the dopamine neurons giving rise to the ascending mesotelencephalic projections also contain the peptide cholecystokinin.