Neural mechanisms of anesthetic induced immobility [microform]
- Bib ID:
- 4653110
- Format:
- Book and Microform
- Author:
- Barter, Linda Susan
- Online Version:
- http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303139
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- Description:
- 122 p.
- ISBN:
- 9780549494324
- Summary:
-
How volatile anesthetics produce the state of general anesthesia is not well understood. The spinal cord is an important site of action for the production of immobility, but beyond this we know little about where anesthetics may act. For halothane, isoflurane and desflurane respectively in Northern Leopard frogs; the immobilizing 50% effective dose (ED50) was 1.4, 1.7 and 6.8% atm, and time required for anesthetic equilibration 510, 480 and 180 minutes. Pithing frogs did not alter isoflurane ED50 or equilibration time. The hind limb wiping reflex was elicited in pithed Northern Leopard frogs anesthetized with 0, 0.4, 0.8 and 1.2 ED50 desflurane. Compared to 0 ED50, 0.4ED50 desflurane significantly reduced the accuracy and pattern but not speed or force of movement. This suggests that the most anesthetic sensitive component of the spinal neural circuitry underlying movement generation in response to noxious stimulus is prior to the level of the motoneuron.
Spinal neurons with ascending projections transmit information involved in multi-limb and bead movements in response to noxious stimuli. No preferential depressant effect of immobilizing doses of halothane, isoflurane or propofol on lumbar dorsal horn neurons with or without projections to the cranial cervical spinal cord or beyond was identified. This suggests that transmission of nociceptive information locally within the spinal cord and to sites more rostrally, within and beyond the spinal cord, are equally affected by anesthetics and not abolished at immobilizing anesthetic doses. Spinal dorsal horn nociceptive specific (NS) and wide dynamic range (WDR) neurons respond to noxious stimuli. Immobilizing doses of halothane and isoflurane depressed noxious-heat evoked responses from NS neurons by 55 and 73% respectively. This effect was partially reversible by the opioid receptor antagonist naloxone, a drug shown not to alter the immobilizing potency of volatile anesthetics.
This suggests that this neuronal depression, although of large magnitude and coincident with the occurrence of immobility, it is not relevant to its production. Effects of volatile anesthetics on dorsal horn neurons, at most, only partially contribute to anesthetic induced immobility. Neural targets warranting further investigation include propriospinal and spinal interneurons involved in pattern generator circuits.
- Notes:
-
- (UMI)AAI3303139
- Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0849.
- Thesis (Ph.D.)--University of California, Davis, 2007.
- Reproduction:
- Microfiche. Ann Arbor, Mich. : University Microfilms International.
- Subject:
- Biology, Neuroscience
- Other authors/contributors:
- University of California, Davis
- Copyright:
-
In Copyright
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- Material type:
- Literary Dramatic Musical
- Published status:
- Unpublished
- Creation date:
- 2007
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