Is the aortic depressor nerve involved in arterial chemoreflexes in rats?

Kobayashi, Masayoshi; Cheng, Zhi; Tanaka, Keizo; Nosaka, Shoichiro

doi:10.1016/s0165-1838(99)00054-5

Cited by 64 publications

(47 citation statements)

References 18 publications

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“…The ADN bipolar stimulating electrodes were connected to a programmable stimulator (Master8; AMPI, Jerusalem, Israel) in series with a stimulus isolator (DS2; Digitimer). Arterial baroreflex responses were evoked by electrical stimulation (8 V, 2-ms pulse duration, 10 s) of the left ADN, which in the rat contains primarily baroreceptor afferents (18). All data were collected during 1-min trials, which included sampling blood pressure and RSNA for 20 s before ADN stimulation, for 10 s during ADN stimulation at a single frequency, and for 25 s after the offset of ADN stimulation.…”

Section: Methodsmentioning

confidence: 99%

“…Four of the barrels of the microinjection pipette were attached to a pressure injection system (BH-2; Medical Systems), and the pipette was secured to a micromanipulator (Kopf Instruments). Local blockade of ␣2-adrenoceptors in the NTS was accomplished by pressure injection of the ␣2-receptor antagonist idazoxan (8,18,30) from the microinjection pipette. In test animals, three of the barrels contained idazoxan in concentrations of 10, 50, and 100 mM, diluted in artificial cerebrospinal fluid (aCSF).…”

Section: Methodsmentioning

confidence: 99%

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α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

Hayward

Riley

Felder

2002

American Journal of Physiology-Heart and Circulatory Physiology

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We examined the effect of ␣2-adrenoreceptor blockade in the nucleus of the solitary tract (NTS) on baroreflex responses elicited by electrical stimulation of the left aortic depressor nerve (ADN) in urethane-anesthetized spontaneously hypertensive rats (SHR, n ϭ 11) and normotensive Wistar-Kyoto rats (WKY, n ϭ 11). ADN stimulation produced a frequencydependent decrease in mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). In SHR, unilateral microinjection of idazoxan into the NTS markedly reduced baroreflex control of MAP, RSNA, and HR and had a disproportionately greater influence on baroreflex control of MAP than of RSNA. In WKY, idazoxan microinjections did not significantly alter baroreflex function relative to control vehicle injections. These results suggest that baroreflex regulation of arterial pressure in SHR is highly dependent on NTS adrenergic mechanisms. The reflex regulation of sympathetic outflow to the kidney is less influenced by the altered ␣ 2-adrenoreceptor mechanisms in SHR.hypertension; medulla; norepinephrine IN HYPERTENSION, the arterial baroreflex is often characterized by a decrease in reflex sensitivity and/or a resetting of reflex function to higher than normal pressures (9,10,15,31,34). In the spontaneously hypertensive rat (SHR), for example, resting blood pressure may be 40-60 mmHg higher than in normotensive rats, and the sigmoid curve describing baroreflex control of mean arterial pressure (MAP) and sympathetic nerve activity is shifted upward but remains parallel to the normal baroreflex curve (9,12,38). In contrast, baroreflex control of heart rate (HR) is markedly attenuated in the SHR (2, 15, 21, 34), despite a resting HR that is comparable to that of its normotensive control, the Wistar-Kyoto rat (WKY). Because baroreflex impairment is present in many forms of hypertension and may contribute to the development and maintenance of the disease (9,10,15,31,34), an understanding of the neurochemical mechanisms involved is of great importance. Neurochemical derangements in hypertension might alter afferent and efferent signaling or integration of baroreceptor information within the central nervous system.In the brain, the medial nucleus of the solitary tract (NTS) in the caudal medulla is the primary central termination site for baroreceptor afferents (16). The integrity of this region is necessary for normal baroreflex control of blood pressure (29). In the SHR and other rat models of hypertension with altered baroreflex function, declines in norepinephrine content and ␣ 2 -adrenoreceptor density within the NTS have been documented (27,33,36,37). Because selective blockade of ␣ 2 -adrenoreceptors in the medial NTS of normotensive subjects can increase resting blood pressure and attenuate baroreflex function (19,30,35), this decline in ␣ 2 -adrenoreceptor density in the NTS of hypertensive animals has been hypothesized to contribute to autonomic dysfunction in these animals. However, the physiological impact of these neurochemical changes o...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

Hayward

Riley

Felder

2002

American Journal of Physiology-Heart and Circulatory Physiology

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“…However, the baroreceptor function in the diabetic state is studied only in the aortic depressor nerve (Fazan, Jr. et al, 1997;Fazan, Jr. et al, 1999;McDowell et al, 1994b;Reynolds et al, 1999) but not in the carotid sinus nerve (Salgado et al, 2001). This may be because there are only baroreceptor afferent fibers and no chemoreceptor afferent fibers in rat aortic depressor nerve unlike the carotid sinus nerve (Fan et al, 1996;Kobayashi et al, 1999;Sapru & Krieger, 1977;Sapru et al, 1981). Based on the results from some studies, there is no evidence to show the changes of the aortic depressor nerve activity in STZ-induced type 1 diabetic rats (Fazan, Jr. et al, 1997;Reynolds et al, 1999;Dall'Ago et al, 2002) and alloxaninduced diabetic rabbits (McDowell et al, 1994b), compared to the sham animals.…”

Section: Changes Of Baroreceptor Afferent Nerve and Terminal In Type mentioning

confidence: 99%

“…Electrical Stimulation of the rat aortic depressor nerve has several advantages to examine the baroreflex function. First, the rat aortic depressor nerve contains only baroreceptor afferent fibers and no chemoreceptor afferent fibers to transmit the chemoreceptor information (Fan et al, 1996;Kobayashi et al, 1999;Sapru & Krieger, 1977;Sapru et al, 1981). Second, the baroreflex induced by stimulating rat aortic depressor nerve is measured without the aortic baroreceptor terminals in the reflex arc, which allows us to specifically examine the role of electrical excitability of aortic baroreceptor in the baroreflex function (second process mentioned above).…”

Section: Role Of Aortic Baroreceptor Neurons In the Arterial Baroreflmentioning

confidence: 99%

Cardiovascular Autonomic Dysfunction in Diabetes as a Complication: Cellular and Molecular Mechanisms

Li¹

2011

Type 1 Diabetes Complications

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“…However, the electrical stimulation of baroreceptor afferents in anesthetized animals has been continued as a useful tool to investigate the reflex regulation of arterial pressure and heart rate in several species, such as dogs, cats, rabbits, swine, and rats (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34).…”

mentioning

confidence: 99%

Acute and chronic electrical activation of baroreceptor afferents in awake and anesthetized subjects

Durand

Fazan

Salgado

et al. 2009

Braz J Med Biol Res

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Electrical stimulation of baroreceptor afferents was used in the 1960's in several species, including human beings, for the treatment of refractory hypertension. This approach bypasses the site of baroreceptor mechanosensory transduction. Chronic electrical stimulation of arterial baroreceptors, particularly of the carotid sinus nerve (Hering's nerve), was proposed as an ultimate effort to treat refractory hypertension and angina pectoris due to the limited nature of pharmacological therapy available at that time. Nevertheless, this approach was abandoned in the early 1970's due to technical limitations of implantable devices and to the development of better-tolerated antihypertensive medications. More recently, our laboratory developed the technique of electrical stimulation of the aortic depressor nerve in conscious rats, enabling access to hemodynamic responses without the undesirable effect of anesthesia. In addition, electrical stimulation of the aortic depressor nerve allows assessment of the hemodynamic responses and the sympathovagal balance of the heart in hypertensive rats, which exhibit a well-known decrease in baroreflex sensitivity, usually attributed to baroreceptor ending dysfunction. Recently, there has been renewed interest in using electrical stimulation of the carotid sinus, but not the carotid sinus nerve, to lower blood pressure in conscious hypertensive dogs as well as in hypertensive patients. Notably, previous undesirable technical outcomes associated with electrical stimulation of the carotid sinus nerve observed in the 1960's and 1970's have been overcome. Furthermore, promising data have been recently reported from clinical trials that evaluated the efficacy of carotid sinus stimulation in hypertensive patients with drug resistant hypertension. Using an electroneurographic approach, the authors demonstrated that in chronic renin-induced hypertensive dogs there were fewer impulses along the carotid sinus nerve than in the normotensive situation. The investigators hypothesized that there is an adaptation within the baroreceptor end organ, which perpetuates, rather than protects against, an elevation in blood pressure. However, in 1958, Warner (2) demonstrated that activation of the baroreflex by direct electrical stimulation of the carotid sinus nerve (Hering's nerve) reduced arterial pressure in anesthetized normotensive dogs for periods lasting up to 90 min. Subsequent work showed that electrical stimulation of the carotid sinus nerve for 10 to 20 s in patients undergoing head and neck surgery elicited similar results,

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Is the aortic depressor nerve involved in arterial chemoreflexes in rats?

Cited by 64 publications

References 18 publications

α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

Cardiovascular Autonomic Dysfunction in Diabetes as a Complication: Cellular and Molecular Mechanisms

Acute and chronic electrical activation of baroreceptor afferents in awake and anesthetized subjects

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Is the aortic depressor nerve involved in arterial chemoreflexes in rats?

Cited by 64 publications

References 18 publications

α2-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

α2-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

Cardiovascular Autonomic Dysfunction in Diabetes as a Complication: Cellular and Molecular Mechanisms

Acute and chronic electrical activation of baroreceptor afferents in awake and anesthetized subjects

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α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats

α₂-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats