It is commonly accepted that general anesthesia produces unconsciousness and amnesia. However, the extent to which the anesthetized brain receives and retains information is not well understood. Memory of a given event relies upon initial consolidation and subsequent retrieval. In order to test the effects of anesthesia on these separate memory components, we compared what rats reported behaviorally with what their brains 'reported' histologically. In chapter 2, we fully anesthetized rats with ketamine/xylazine anesthesia and exposed the animals to a novel odorant mixture. The following day the rats were presented with the same odorant mixture while awake in order to assess behavioral familiarity. The rats demonstrated no memory of the odorants previously presented during anesthesia. In order to assess odor-induced brain changes, rats were sacrificed for histological analysis 2 hours after exposure to the odorants during anesthesia, or 2 hours after re-exposure while awake the following day. We quantified the protein expression of c-fos, an immediate early gene thought to be critical for memory consolidation, in cortical olfactory regions. During anesthesia, a novel odorant mixture activated c-Fos similar to that found in awake animals. Repeated exposure to the odorants caused an attenuation of c-Fos regardless of whether the initial exposure occurred while anesthetized or awake. This suggests that memory-related protein changes can occur in olfactory cortical regions despite anesthesia. Given, the potential information consolidation observed in these ketamine/xylazine anesthetized animals, we attempted to retrieve olfactory memories using additional behavioral paradigms and memory-enhancing drugs in chapter 3, but were unable to reveal any explicit memory formation. However, we found subtle changes in odorant approach latency, suggesting a potential implicit memory. Further histological investigation in chapter 4 revealed that changes in odor-induced neurogenesis could also occur despite ketamine/xylazine anesthesia, similar to that found with c-Fos labeling, thus supporting the permissive role of this anesthetic. However, odor-related changes in c-Fos did not occur with the anesthetics pentobarbital or propofol, suggesting these traits are not universal amongst all anesthetics. Nevertheless, these data indicate a functional disconnection between the cortical representation of an environmental stimulus and the corresponding perceptual experience or memory.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08022011-143415 |
| Date | 02 August 2011 |
| Creators | Samuelsson, Andrew R. |
| Contributors | Nathan Urban, Yan Xu, Keith Miller, Kathy Albers, Gregg Homanics, Edda Thiels |
| 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-08022011-143415/ |
| Rights | restricted, 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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