Patterning of somatosympathetic reflexes

1999 ◽  
Vol 277 (3) ◽  
pp. R716-R724 ◽  
Author(s):  
I. A. Kerman ◽  
B. J. Yates
Keyword(s):  
Nerve Stimulation ◽  
Sympathetic Nerve ◽  
Vestibular Stimulation ◽  
Specific Pattern ◽  
External Carotid ◽  
Renal Nerve ◽  
Muscle Afferent ◽  
Somatosympathetic Responses ◽  
Sympathetic Nerve Activation ◽  
Vestibulosympathetic Reflexes

In a previous study, we reported that vestibular nerve stimulation in the cat elicits a specific pattern of sympathetic nerve activation, such that responses are particularly large in the renal nerve. This patterning of vestibulosympathetic reflexes was the same in anesthetized and decerebrate preparations. In the present study, we report that inputs from skin and muscle also elicit a specific patterning of sympathetic outflow, which is distinct from that produced by vestibular stimulation. Renal, superior mesenteric, and lumbar colonic nerves respond most strongly to forelimb and hindlimb nerve stimulation (∼60% of maximal nerve activation), whereas external carotid and hypogastric nerves were least sensitive to these inputs (∼20% of maximal nerve activation). In contrast to vestibulosympathetic reflexes, the expression of responses to skin and muscle afferent activation differs in decerebrate and anesthetized animals. In baroreceptor-intact animals, somatosympathetic responses were strongly attenuated (to <20% of control in every nerve) by increasing blood pressure levels to >150 mmHg. These findings demonstrate that different types of somatic inputs elicit specific patterns of sympathetic nerve activation, presumably generated through distinct neural circuits.

Regional and functional differences in the distribution of vestibulosympathetic reflexes

1998 ◽  
Vol 275 (3) ◽  
pp. R824-R835 ◽  
Author(s):  
I. A. Kerman ◽  
B. J. Yates
Keyword(s):  
Blood Pressure ◽  
Vestibular System ◽  
Sympathetic Nerves ◽  
Relative Magnitude ◽  
External Carotid ◽  
Sympathetic Outflow ◽  
Renal Nerve ◽  
Body Regions ◽  
Sympathetic Efferents ◽  
Vestibulosympathetic Reflexes

Although considerable evidence suggests that the vestibular system regulates sympathetic outflow during movement and changes in posture, little is known about relative vestibular influences on activity of different sympathetic nerves and sympathetic efferents with different functions. In the present study, we demonstrated that electrical stimulation of the vestibular nerve in the cat elicited responses in sympathetic nerves innervating the head and abdominal viscera. This observation suggests that activity of sympathetic efferents innervating multiple body regions is affected by vestibular signals. These responses were attenuated by >80% when blood pressure was increased to >160 mmHg. Because raising blood pressure decreases the responsiveness of vasoconstrictor fibers, the simplest explanation for these data is that the vestibular system provides particularly strong inputs to components of the sympathetic nervous system that regulate peripheral vascular resistance. Furthermore, the relative magnitude of vestibulosympathetic reflexes was over four times larger in one sympathetic nerve composed mainly of vasoconstrictor efferents (renal nerve) than another nerve (external carotid nerve) containing similar types of fibers. Collectively, these data indicate that the vestibular system has selective influences on sympathetic outflow to particular tissues and body regions.

Postjunctional α2-adrenoceptors are not present in proximal arterioles of rat intestine

1998 ◽  
Vol 274 (1) ◽  
pp. H202-H208 ◽  
Author(s):  
Geoffrey P. Nase ◽  
Matthew A. Boegehold
Keyword(s):  
Shear Stress ◽  
Nerve Stimulation ◽  
Sympathetic Nerve ◽  
Receptor Activation ◽  
Sympathetic Nerve Stimulation ◽  
No Release ◽  
Before And After ◽  
Sympathetic Nerve Activation ◽  
Intestinal Submucosa ◽  
Resting Tone

The purpose of this study was to evaluate two potential stimuli for nitric oxide (NO) release in rat intestinal arterioles during sympathetic nerve activation. To determine whether these vessels contain endothelial α2-adrenoceptors linked to thel-arginine-NO pathway, intravital microscopy was used to study the response of first-order arterioles (1As, 20–40 μm ID) to direct application of 1) the selective α2-agonist BHT-933 and 2) norepinephrine (NE) or sympathetic nerve stimulation before and after α1- or α2-receptor blockade. The effect of sympathetic nerve stimulation on 1A wall shear rate (WSR) was also determined to evaluate the possibility of hemodynamic shear stress as a stimulus for NO release. BHT-933 had no effect on 1A diameter, whereas NE produced dose-dependent constrictions of 5 ± 3 to 15 ± 3 μm, which were usually abolished by the α1-antagonist prazosin but unaffected by the α2-antagonist idazoxan. Sympathetic nerve stimulation at 3, 8, and 16 Hz induced constrictions of 4 ± 1, 8 ± 2, and 17 ± 4 μm, respectively, and these constrictions were also usually abolished by prazosin but unaffected by idazoxan. Resting WSR averaged 1,997 ± 163 s−1 and decreased to 1,587 ± 209, 1,087 ± 195, and 537 ± 99 s−1 during 3-, 8-, and 16-Hz nerve stimulation. These results suggest that α2-adrenoceptor-dependent pathways do not influence either resting tone or sympathetic constriction of proximal arterioles in the intestinal submucosa and that luminal shear stress in these vessels significantly decreases with sympathetic constriction. It therefore appears unlikely that either α2-receptor activation or changes in hemodynamic shear serve as stimuli for arteriolar NO release during periods of increased sympathetic nerve activity.

Visceral afferent activation-induced changes in sympathetic nerve activity and baroreflex sensitivity

1999 ◽  
Vol 276 (6) ◽  
pp. R1780-R1791 ◽  
Author(s):  
Tarek M. Saleh ◽  
Barry J. Connell ◽  
Gary V. Allen
Keyword(s):  
Vagus Nerve ◽  
Nerve Stimulation ◽  
Sympathetic Nerve ◽  
Baroreflex Sensitivity ◽  
Sympathetic Nerve Activity ◽  
Parabrachial Nucleus ◽  
Sprague Dawley ◽  
Nerve Activity ◽  
Renal Nerve ◽  
Relative Contribution

The following experiments were done to determine whether changes in baroreflex sensitivity evoked by cervical vagus nerve stimulation are due to sympathoexcitation mediated by the parabrachial nucleus. The relative contribution of cardiopulmonary and general gastric afferents within the cervical vagus nerve to the depression in baroreflex sensitivity are also investigated. Male Sprague-Dawley rats anesthetized with thiobutabarbital sodium (50 mg/kg) were instrumented to measure blood pressure and heart rate or for the continuous monitoring of renal sympathetic nerve activity. Baroreflex sensitivity was measured using bolus injections of phenylephrine. Electrical stimulation of the cervical vagus (with or without the aortic depressor nerve) or the abdominal vagus nerve produced a significant increase in renal nerve activity and a decrease in baroreflex sensitivity. Both of these effects were blocked after the microinjection of lidocaine into the parabrachial nucleus before nerve stimulation. Therefore, we conclude that an increase in the activity of cardiac, pulmonary, or general gastric afferents mediated the increased sympathetic output and decreased baroreflex sensitivity via a pathway involving the parabrachial nucleus.

Interactive Effects of Verapamil and Sympathetic Nerve Stimulation on the Sinus and AV Nodes in the Canine Hearts.

1992 ◽  
Vol 33 (1) ◽  
pp. 83-93 ◽  
Author(s):  
Katsusuke YANO ◽  
Masanobu HIRATA ◽  
Takao MITSUOKA ◽  
Yoriaki MATSUMOTO ◽  
Tetsuya HIRATA ◽  
...  
Keyword(s):  
Nerve Stimulation ◽  
Sympathetic Nerve ◽  
Interactive Effects ◽  
Sympathetic Nerve Stimulation

Neurotransmission in the medulla mediating insular cortical and lateral hypothalamic sympathetic responses

1998 ◽  
Vol 76 (7-8) ◽  
pp. 737-746 ◽  
Author(s):  
Kenneth S Butcher ◽  
David F Cechetto
Keyword(s):  
Receptor Antagonist ◽  
Sympathetic Nerve ◽  
Pressor Response ◽  
Ventrolateral Medulla ◽  
Bipolar Electrode ◽  
Hypothalamic Area ◽  
Renal Nerve ◽  
Lateral Hypothalamic ◽  
Baseline Activity ◽  
Sympathetic Responses

Previous evidence has shown sympathetic nerve responses to insular cortical (IC) stimulation are mediated by synapses within the lateral hypothalamic area (LHA) and ventrolateral medulla (VLM). The present study was aimed at determining the neurotransmitter(s) and receptor(s) involved at the synapse in the VLM. Twenty male Wistar rats were instrumented for renal nerve, arterial pressure, and heart rate recording. The IC or the LHA was stimulated with a bipolar electrode (200-1000 µA; 2 ms; 0.8 Hz) to elicit sympathetic nerve responses. Antagonists were then pressure-injected into the VLM (300 nL). Bilateral and unilateral kynurenate (25 mM) resulted in 100% block of IC- and LHA-stimulated sympathetic nerve responses. Bilateral injection of the non-NMDA (N-methyl-D-aspartate) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 200 µM) also resulted in up to 100% block of IC and LHA sympathetic responses. In addition, unilateral injections of CNQX were made in two animals, resulting in 100 and 83% block of LHA sympathetic responses. Bilateral injection of the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (AP5; 200µM) did not affect the response to IC or LHA stimulation. Kynurenate, CNQX, and AP5 all resulted in an elevation of baseline sympathetic nerve activity and a pressor response. Kynurenate resulted in a 263 ± 79% increase in baseline activity, while CNQX and AP5 resulted in 83 ± 19% and 91 ± 21% increases, respectively. Bilateral injections of antagonists for GABAA (bicuculline; 0.1 µM), acetylcholine (atropine; 0.1 µM) and catecholaminergic alpha and beta receptors (phentolamine and propranolol: 0.1 µM) had no effect on LHA sympathetic responses. Thus, sympathetic responses originating in the IC and LHA are mediated by a non-NMDA receptors in the VLM, which are likely AMPA receptors.Key words: insular cortex, ventrolateral medulla, glutamate, sympathetic activity.

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