Nts, cih


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 stimulation are enhanced, the effect of CIH on the central components, in particular NTS, is still not completely 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-unit extracellular recording technique, we recorded NTS barosensitive neurons in response to arterial pressure (AP) changes induced by descending aorta occlusion. Our data indicated that 1) the mean arterial pressure and HR were similar in RA control and CIH groups. 2) The majority of neurons from RA and CIH NTS neurons increased firing rate, whereas other neurons decreased firing 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 firing rate than RA early neurons, whereas CIH did not change the firing rate in late neurons. 5) For late neurons, HR reduction correlated with neuronal activity. HR reduction-neuronal activity increase 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 neurons have both early and late neurons, CIH selectively enhances neuron activity in response to AP changes in NTS early neurons and attenuate the baroreflex bradycardia. Along our previous work that CIH-induced the cell loss in the nucleus ambiguus (NA), we conclude that CIH attenuates the functions of NA, whereas enhances the NTS functions to compensate for the loss of function in NA


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Graduation Date





Cheng, Zixi (Jack)


Master of Science (M.S.)


College of Medicine


Molecular Biology and Microbiology

Degree Program









Release Date

December 2015

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)


Dissertations, Academic -- Medicine; Medicine -- Dissertations, Academic