The mediodorsal nucleus of the thalamus (MD) represents the main subcortical structure that projects to the prefrontal cortex (PFC) and regulates key aspects of the cognitive functions of this region. Within the PFC, GABA local circuit neurons shape the activity patterns and hence the memory fields of pyramidal cells. Although the connections between the MD and PFC are well established, little attention has been given to the functional connections between projecting fibers from the MD and different subclasses of GABA cells in the PFC. In order to address this issue in the rat, we examined MD axons labeled by tract-tracing in combination with immunogold-silver to identify different calcium binding proteins localized within separate populations of interneurons. Electron micrographic examination of PFC sections from these animals revealed that MD terminals made primarily asymmetric synapses onto dendritic spines and less commonly onto dendritic shafts. Most of the dendrites receiving MD synaptic input were immunoreactive for parvalbumin (ParV), whereas dendrites labeled for calretinin or calbindin received synapses from MD fibers less frequently. We also observed that some MD terminals were themselves immunoreactive for calcium binding proteins, again more commonly for ParV. These results suggest that the MD exerts a dual influence on PFC pyramidal cells: direct inputs onto spines and an indirect influence mediated via synapses onto each subclass of interneurons. The preferential input to ParV cells endows MD afferents with a strong indirect influence on pyramidal cell activity by virtue of ParV cell synapses onto soma, proximal dendrites and axon initial segments.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08172004-235130 |
| Date | 05 October 2004 |
| Creators | Rotaru, Diana Codruta |
| Contributors | Susan Sesack, Pat Card, German Barrionuevo |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-08172004-235130/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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