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Dissertation
Topographic and neurochemical organization of the dorsal raphe nucleus with respect to the trigeminal somatosensory pathway in the rat
Doctor of Philosophy (Ph.D.), Medical College of Pennsylvania and Hahnemann University
Jul 1999
DOI:
https://doi.org/10.17918/00009724
Abstract
The dorsal raphe (DR) has been the focus of extensive research. While the global distribution of the DR and its impact on selected brain regions has been previously investigated, less is known about the organization of this efferent system with respect to specific sensory pathways. The goal of this project was to explore the anatomical relationship between the DR and the rat trigeminal somatosensory pathway (TSP). In particular we examined (1) the distribution and organization of DR-TSP projection neurons; (2) the location and patterns of branching of DR neurons which branch to multiple relay sites along the TSP; (3) neurochemical identity of DR-TSP projection neurons. Adult Long Evans hooded rats received three pressure injections of different fluorescent retrograde tracers into sites along the TSP. Following these injections, coronal sections through the DR were examined by fluorescence microscopy. Cells through these sections were counted and mapped indicating the location and distribution of DR projection cells to the TSP. In the second component of this study, combinations of fluorescent retrograde tracers noted within single DR neurons were studied to determine the degree in which individual neurons may influence signal transmission along the trigeminal sensory pathway. The presence of multiple tracers within cell bodies of single neurons provided evidence that individual DR cells concurrently innervate multiple structures along the TSP via axon branching. The third goal of this study was to determine the neurochemical identity of DR neurons that project to the trigeminal sensory pathway. Previous investigators have determined that the rat DR consisted primarily of serotonin (5HT), dopamine (DA) and gamma-aminobutyric acid (GABA) containing neurons. Although subregions within the DR are organized with respect to cortical and subcortical targets, we could not confirm a clear organization of DR branching neurons with respect to TSP. The dorsomedial and ventromedial subregions contained branching neurons which projected to all three levels of the TSP. In immunochemical studies, 5HT was noted in DR projection neurons to all three levels of the TSP. This study found that 80% of 5HT neurons within DR subregions also stained positively for GAD or GABA. (Abstract shortened by UMI.).
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Details
- Title
- Topographic and neurochemical organization of the dorsal raphe nucleus with respect to the trigeminal somatosensory pathway in the rat
- Creators
- Michael L. Kirifides
- Contributors
- Barry D. Waterhouse (Advisor) - Drexel University, Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Awarding Institution
- Medical College of Pennsylvania and Hahnemann University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Medical College of Pennsylvania and Hahnemann University; Philadelphia, Pennsylvania
- Number of pages
- xv, 196 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Medicine (1993-1996, 1998-2002); Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Other Identifier
- 991021889012704721