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Functional Identification of Nucleus Tractus Solitarius (NTS) Barosensitive Neurons: Effect of Chronic Intermittent Hypoxia (CIH)

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Date Issued:
2015
Abstract/Description:
Chronic Intermittent Hypoxia (CIH) is a model used to study obstructive sleep apnea (OSA). Previously, we showed that baroreflex control of heart rate (HR) (baroreflex sensitivity) is reduced in CIH rats. While afferent function and HR in response to vagal efferent stimulationare enhanced, the effect of CIH on the central components, in particular NTS, is still notcompletely understood. F344 rats (3-4 mo) were exposed either to CIH or room air (RA) for 35-50 days. Following CIH exposure, rats were anaesthetized with Ket/Ace. Using single-unitextracellular recording technique, we recorded NTS barosensitive neurons in response to arterialpressure (AP) changes induced by descending aorta occlusion. Our data indicated that 1) themean arterial pressure and HR were similar in RA control and CIH groups. 2) The majority ofneurons from RA and CIH NTS neurons increased firing rate, whereas other neurons decreasedfiring upon AP elevation. 3) In 27 RA and 31 CIH NTS neurons with increased firing rate, 15 RA and 15 CIH neurons were activated at a low ?MAP at the early phase of AP increase (early neurons); whereas 12 RA neurons and 16 CIH neurons were activated at a late phase of AP increase (late neurons). The early neurons rapidly increased their firing during the rising phase of MAP, whereas late neurons did not increase their firing until the ?MAP reached its peak. 4) Early neuron activity-?MAP relationship was further characterized by the logistic sigmoid function curve. CIH significantly increased the maximal gain of the neuron activity-?MAP curve and the range of the response. In addition, CIH early neurons had a significantly higher firingrate than RA early neurons, whereas CIH did not change the firing rate in late neurons. 5) Forlate neurons, HR reduction correlated with neuronal activity. HR reduction-neuronal activityincrease curve was shifted to the right in CIH neurons, indicating that CIH decreased HR control in response to NTS firing increase. Collectively, our data suggest that NTS barosensitive neuronshave both early and late neurons, CIH selectively enhances neuron activity in response to APchanges in NTS early neurons and attenuate the baroreflex bradycardia. Along our previous workthat CIH-induced the cell loss in the nucleus ambiguus (NA), we conclude that CIH attenuatesthe functions of NA, whereas enhances the NTS functions to compensate for the loss of functionin NA
Title: Functional Identification of Nucleus Tractus Solitarius (NTS) Barosensitive Neurons: Effect of Chronic Intermittent Hypoxia (CIH).
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Name(s): Kolpakova, Jenya, Author
Cheng, Zixi, Committee Chair
Naser, Saleh, Committee Member
Kim, Yoon-Seong, Committee Member
Ebert, Steven, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2015
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Chronic Intermittent Hypoxia (CIH) is a model used to study obstructive sleep apnea (OSA). Previously, we showed that baroreflex control of heart rate (HR) (baroreflex sensitivity) is reduced in CIH rats. While afferent function and HR in response to vagal efferent stimulationare enhanced, the effect of CIH on the central components, in particular NTS, is still notcompletely understood. F344 rats (3-4 mo) were exposed either to CIH or room air (RA) for 35-50 days. Following CIH exposure, rats were anaesthetized with Ket/Ace. Using single-unitextracellular recording technique, we recorded NTS barosensitive neurons in response to arterialpressure (AP) changes induced by descending aorta occlusion. Our data indicated that 1) themean arterial pressure and HR were similar in RA control and CIH groups. 2) The majority ofneurons from RA and CIH NTS neurons increased firing rate, whereas other neurons decreasedfiring upon AP elevation. 3) In 27 RA and 31 CIH NTS neurons with increased firing rate, 15 RA and 15 CIH neurons were activated at a low ?MAP at the early phase of AP increase (early neurons); whereas 12 RA neurons and 16 CIH neurons were activated at a late phase of AP increase (late neurons). The early neurons rapidly increased their firing during the rising phase of MAP, whereas late neurons did not increase their firing until the ?MAP reached its peak. 4) Early neuron activity-?MAP relationship was further characterized by the logistic sigmoid function curve. CIH significantly increased the maximal gain of the neuron activity-?MAP curve and the range of the response. In addition, CIH early neurons had a significantly higher firingrate than RA early neurons, whereas CIH did not change the firing rate in late neurons. 5) Forlate neurons, HR reduction correlated with neuronal activity. HR reduction-neuronal activityincrease curve was shifted to the right in CIH neurons, indicating that CIH decreased HR control in response to NTS firing increase. Collectively, our data suggest that NTS barosensitive neuronshave both early and late neurons, CIH selectively enhances neuron activity in response to APchanges in NTS early neurons and attenuate the baroreflex bradycardia. Along our previous workthat CIH-induced the cell loss in the nucleus ambiguus (NA), we conclude that CIH attenuatesthe functions of NA, whereas enhances the NTS functions to compensate for the loss of functionin NA
Identifier: CFE0005967 (IID), ucf:50806 (fedora)
Note(s): 2015-12-01
M.S.
Medicine, Molecular Biology and Micro
Masters
This record was generated from author submitted information.
Subject(s): NTS -- CIH
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0005967
Restrictions on Access: public 2015-12-15
Host Institution: UCF

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