Dorsal root afferent influences on tonic firing of renal and mesenteric sympathetic nerves in rats

1993 ◽  
Vol 264 (6) ◽  
pp. R1193-R1199 ◽  
Author(s):  
R. B. Taylor ◽  
L. C. Weaver
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Sympathetic Nerves ◽  
Renal Nerve ◽  
Dorsal Rhizotomy ◽  
Renal Nerve Activity ◽  
Afferent Discharge ◽  
High Cervical ◽  
Sympathetic Discharge ◽  
Nerve Discharge

After spinal cord transection in cats and rats, the activity of many sympathetic nerves is not entirely lost, and firing of other nerves continues unabated or is increased. This study was done to evaluate the importance of dorsal root afferent discharge on the generation of tonic sympathetic activity in renal and mesenteric postganglionic nerves in spinal rats and in rats with intact neuraxes. Sympathetic discharge was recorded in anesthetized rats, and peripheral afferent influences were eliminated by dorsal rhizotomy from T4 to L2. Activity of renal and mesenteric nerves was well maintained after high cervical and thoracic (T4) cord transections. Rhizotomy had no effect on sympathetic discharge in rats with intact neuraxes but decreased renal nerve activity significantly (-25%) in spinal rats. Because rhizotomy decreased mesenteric discharge in only three of six spinal rats, mean mesenteric nerve discharge was not decreased significantly. The decreased renal nerve discharge after dorsal rhizotomy could not be attributed to input from any specific spinal segment, and ipsilateral input was no greater than contralateral input. After rhizotomy, both renal and mesenteric nerves had substantial excitatory drive from the transected, deafferented spinal cord. These findings demonstrate that dorsal root afferent influences on spinal neurons can contribute to the generation of tonic discharge in some sympathetic nerves in spinal animals.

Effects of spinal cord transection on sympathetic discharge in decerebrate-unanesthetized cats

1989 ◽  
Vol 257 (6) ◽  
pp. R1506-R1511 ◽  
Author(s):  
L. C. Weaver ◽  
R. D. Stein
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Spectral Analysis ◽  
Spinal Cord Transection ◽  
Renal Nerves ◽  
Frequency Range ◽  
Renal Nerve ◽  
Sympathetic Discharge ◽  
Nerve Discharge

Previous experiments in our laboratory have shown that discharge of splenic, mesenteric, and splanchnic nerves is well maintained after spinal cord transection in chloralose-anesthetized cats (8, 9, 11). The primary purpose of this investigation was to determine if maintained sympathetic discharge could be observed after spinal transection in the absence of chloralose anesthesia. In cats anesthetized with alphaxalone-alphadolone, changes in splanchnic discharge, blood pressure, and heart rate caused by decerebration and removal of the forebrain were observed. This procedure decreased blood pressure, increased heart rate, and had no immediate effect on sympathetic discharge or its rhythm (assessed by power density spectral analysis). One hour after decerebration and termination of anesthesia, splanchnic discharge had increased by approximately 36%. Next, effects of spinal cord transection on discharge of splanchnic, mesenteric, and renal nerves were observed in the decerebrate-unanesthetized cats. Splanchnic discharge decreased by 50%, mesenteric nerve discharge was unchanged, and renal nerve discharge decreased by 97%. Therefore, splanchnic nerve discharge was not as well maintained in decerebrate-unanesthetized cats as it had been in chloralose-anesthetized animals, and the remaining splanchnic discharge appeared to affect mesenteric nerves preferentially. Finally, spectral analysis of the splanchnic discharge demonstrated that before cord transection, most of the signal was in the 0- to 6-Hz frequency range, whereas after transection the proportion of signal in this frequency range was significantly reduced and the proportion in higher frequencies (7-25 Hz) was significantly increased. This loss of low-frequency rhythmicity is consistent with findings in our previous studies in chloralose-anesthetized cats.

Spinal stimulation to locate preganglionic neurons controlling the kidney, spleen, or intestine

1992 ◽  
Vol 263 (4) ◽  
pp. H1026-H1033 ◽  
Author(s):  
R. B. Taylor ◽  
L. C. Weaver
Keyword(s):  
Spinal Cord ◽  
Sympathetic Outflow ◽  
Renal Nerve ◽  
Homocysteic Acid ◽  
Sympathetic Control ◽  
The Third ◽  
Preganglionic Neurons ◽  
Spinal Segments ◽  
Vascular Beds ◽  
Nerve Discharge

The organization of sympathetic preganglionic neurons may be a substrate for selective control of sympathetic outflow to different vascular beds. This study was done to determine the spinal segments containing preganglionic neurons controlling discharge of renal, splenic, and mesenteric postganglionic nerves. In urethan-anesthetized rats, preganglionic neurons were stimulated by microinjecting D,L-homocysteic acid (3 nl, 0.17 M) into the lateral gray matter of the third thoracic (T3) to the fourth lumbar (L4) spinal segments. Responses from all three nerves could be elicited from segments T4-T13. The greatest increases in renal nerve discharge were evoked from segments T8-T12, the largest increase of 59 +/- 9% elicited from T10. Increases in splenic and mesenteric nerve discharge were smaller and were evoked more uniformly from T4-L3. The largest increases in discharge of splenic and mesenteric nerves were 19 +/- 5% (from T5) and 26 +/- 4% (from T10), respectively. The widely overlapping spinal cord segments controlling these three organs suggest that location of the preganglionic neurons in different spinal segments is not part of the mechanism for selective sympathetic control. However, the larger renal nerve responses demonstrate that sympathetic output to these organs can be differentiated at the level of the spinal cord.

Renorenal reflexes: neural components of ipsilateral and contralateral renal responses

1985 ◽  
Vol 249 (4) ◽  
pp. F507-F517 ◽  
Author(s):  
U. C. Kopp ◽  
L. A. Smith ◽  
G. F. DiBona
Keyword(s):  
Spinal Cord ◽  
Venous Pressure ◽  
Urinary Sodium Excretion ◽  
Reflex Response ◽  
Nerve Activity ◽  
Renal Nerve ◽  
Electrophysiological Responses ◽  
Renal Nerve Activity ◽  
Renal Vascular ◽  
Renal Responses

In anesthetized rats, stimulating renal mechanoreceptors (MR) by increasing renal venous pressure (RVP) 22 mmHg increased ipsilateral (ipsi) renal vascular resistance (RVR) from 23.5 to 31.3 mmHg/(ml X min-1 X g-1), ipsi urinary sodium excretion (UNaV) from 0.26 to 0.49 mumol X min-1 X g-1, contralateral (contra) urine flow rate (V) from 3.13 to 4.43 microliter X min-1 X g-1, and UNaV from 0.30 to 0.46 mumol X min-1 X g-1. Ipsi renal denervation (DNX) did not affect the increase in ipsi RVR but reduced the increase in ipsi UNaV. The increases in contra V and UNaV were abolished by either ipsi or contra renal DNX. Increases RVP increased ipsi afferent renal nerve activity (ARNA) 288 counts/10 s and decreased ipsi and contra efferent renal nerve activity (ERNA) 242 and 490 counts/10 s, respectively. Renal pelvic instillation of lidocaine (5 micrograms/ml) did not affect the renal functional or electrophysiological responses to increases RVP but abolished the increase in ipsi ARNA, the decrease in contra ERNA, and the increases in contra V and UNaV produced by increasing ureteral pressure (UP) or retrograde ureteropelvic perfusion with 0.9 M NaCl [chemoreceptor (CR) stimulation]. Chronic T6 spinal cord section abolished the increase in ipsi ARNA, the decrease in contra ERNA, and the increases in contra V and UNaV produced by renal MR (increases RVP, increases UP) and CR stimulation. We conclude increases that RVP results in an ipsi and contra inhibitory renorenal reflex. Differential blockade with pelvic lidocaine suggests that the sensory receptors activated by increases RVP are located in an anatomically different area than those activated by increases UP or retrograde ureteropelvic perfusion with 0.9 M NaCl. An intact spinal cord is required for the normal responsiveness of renal sensory neuroreceptor complexes to specific stimuli in the context of the complete renorenal reflex response.

Contribution of renal sympathetic nerves to the urinary excretion of norepinephrine

1982 ◽  
Vol 60 (8) ◽  
pp. 1067-1072 ◽  
Author(s):  
Rodnhy W. Lappe ◽  
David P. Henry ◽  
Lynn R. Willis
Keyword(s):  
Urinary Excretion ◽  
Sympathetic Nerves ◽  
Tubular Secretion ◽  
Renal Nerves ◽  
Renal Nerve ◽  
Group Iii ◽  
Group I ◽  
Renal Nerve Activity ◽  
Renal Sympathetic ◽  
Stimulation Of

Increased activity of the renal sympathetic nerves may result in increased urinary excretion of norepinephrine (NE). In the present study, unilateral electrical stimulation of the renal nerves of the rabbit was employed to test this hypothesis. Stimulation of the renal nerves to one kidney at 2 Hz (group I) produced no significant alteration of plasma NE concentration, glomerular filtration rate (GFR), or NE excretion by either kidney. Stimulation at 4 Hz (group II) caused statistically significant reductions of GFR and urine flow in experimental kidneys, but the urinary excretion of NE, per millilitre GFR, and the CNE/GFR ratios were significantly greater than prestimulation values. In another group of animals (group III), an inhibitor of cation-specific tubular transport, cyanine 863 (6 mg/kg, i.v.), significantly reduced the prestimulation urinary excretion of NE by 60–70% when compared with that of groups I or II. Stimulation of the renal nerves (4 Hz) in the animals of group III caused a significant reduction in GFR in the experimental kidney but did not alter the urinary excretion of NE or the CNE/GFR ratios. The results of these studies indicate that an increase in renal nerve activity causes an increase in the urinary excretion of NE, and that tubular secretion is responsible for the excretion of the neuronally released catecholamine.

Reflex variability in selective dorsal rhizotomy

1993 ◽  
Vol 79 (3) ◽  
pp. 346-353 ◽  
Author(s):  
Ira P. Weiss ◽  
Steven J. Schiff
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Selection Method ◽  
Selective Dorsal Rhizotomy ◽  
Content Type ◽  
Reflex Responses ◽  
Dorsal Rhizotomy ◽  
Spatial Facilitation ◽  
Reflex Threshold ◽  
Fine Print

✓ The variability of reflex responses during selective dorsal rhizotomy was studied in eight children between the ages of 3 and 7 years. For a given dorsal root or rootiet, the electrical reflex threshold and response varied considerably when observed over several minutes. Changes in electrode pressure, mechanical dissection of the root, and reflex spatial facilitation were all found to contribute to the variability. Even when electrode pressure was held constant, intrinsic spinal cord reflex variability substantially weakened the predictability of the intraoperative selection method used during this surgery.

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