The ontogeny of nociception and anti-nociception in the fetal and infant rat spinal cord using Fos protein as a marker.
Item
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Title
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The ontogeny of nociception and anti-nociception in the fetal and infant rat spinal cord using Fos protein as a marker.
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Identifier
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AAI9830779
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identifier
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9830779
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Creator
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Yi, Duckhyun Kim.
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Contributor
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Adviser: Gordon A. Barr
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Physiological | Psychology, Psychometrics | Psychology, Behavioral | Biology, Neuroscience
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Abstract
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The first experiment examined the maturation of nociceptive primary afferents in awake 0, 1, 2, 3, and 14 day old rats. Pinch, immersion in hot water, or formalin injection was applied to the hindpaw. On the day of birth, all 3 stimuli elicited Fos immunoreactivity in dorsal horn cells. Fos expression was age and stimulus type dependent. The second experiment examined the appearance of Fos protein in response to formalin injection in fetal day (FD) 19, 20 and 21 animals. Very few cells showed Fos at FD 19, and the number of Fos nuclei first appeared in significant numbers at fetal age 20. There was a large increase in the number of Fos labeled nuclei between FD 20 and 21.;Experiment 3 examined the inhibition of formalin-induced Fos immunoreactivity in the spinal cord following different anesthetic treatments: a mixture of xylazine and ketamine, methoxyflurane, acepromazine and hypothermia. All treatments induced behavioral anesthesia. Despite the anesthesia, the ketamine-xylazine mixture was completely ineffective in suppressing Fos immunoreactivity. In contrast, methoxyflurane and hypothermia blocked the appearance of Fos protein following formalin injection. Mechanisms by which these agents produce anesthesia are discussed.;The effects of ICV morphine administration on behavior and Fos immunoreactivity in the spinal cord following formalin injection or application of noxious heat in the paw pad of 3 and 14 day old rats were studied. Pups injected with formalin showed profound analgesia in both the forepaw and hindpaw following ICV morphine administration whereas in the thermal test, the hindpaw was never analgesic. However, ICV morphine administration reduced the number of Fos stained nuclei in both the formalin and thermal test. The behavioral data suggest that development of analgesia is a function of both stimulus types and the body part stimulated. The Fos data suggest that mechanisms by which morphine is producing its analgesic effects, such as descending inhibitory control system, are immature during the early postnatal period.;Taken together, these results suggest that (1) nociceptors are functional before birth and undergo significant postnatal maturation, (2) the discrepancy between behavior and Fos suppression exists both during pain processing and dampening, (3) Fos expression is not a good predictor of behavioral analgesia, and (4) discrepancy between Fos immunoreactivity and behavior is exaggerated depending on the type of noxious stimulus.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
