Title

Selective Impairment Of Central Mediation Of Baroreflex In Anesthetized Young Adult Fischer 344 Rats After Chronic Intermittent Hypoxia

Keywords

Baroreceptor afferent; Brain stem; Cardiac ganglia; Heart; Parasympathetic efferent

Abstract

Baroreflex control of heart rate (HR) is impaired after chronic intermittent hypoxia (CIH). However, the location and nature of this response remain unclear. We examined baroreceptor afferent, vagal efferent, and central components of the baroreflex circuitry. Fischer 344 (F344) rats were exposed to room air (RA) or CIH for 35-50 days and were then anesthetized with isoflurane, ventilated, and catheterized for measurement of mean arterial blood pressure (MAP) and HR. Baroreceptor function was characterized by measuring percent changes of integrated aortic depressor nerve (ADN) activity (Int ADNA) relative to the baseline value in response to sodium nitroprusside- and phenylephrine-induced changes in MAP. Data were fitted to a sigmoid logistic function curve. HR responses to electrical stimulation of the left ADN and the right vagus nerve were assessed under ketamine-acepromazine anesthesia. Compared with RA controls, CIH significantly increased maximum baroreceptor gain or maximum slope, maximum Int ADNA, and Int ADNA range (maximum - minimum Int ADNA), whereas other parameters of the logistic function were unchanged. In addition, CIH increased the maximum amplitude of bradycardic response to vagal efferent stimulation and decreased the time from stimulus onset to peak response. In contrast, CIH significantly reduced the maximum amplitude of bradycardic response to left ADN stimulation and increased the time from stimulus onset to peak response. Therefore, CIH decreased central mediation of the baroreflex but augmented baroreceptor afferent function and vagal efferent control of HR.

Publication Date

11-1-2007

Publication Title

American Journal of Physiology - Heart and Circulatory Physiology

Volume

293

Issue

5

Number of Pages

-

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1152/ajpheart.00358.2007

Socpus ID

36148956735 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/36148956735

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