Lumbar Sympathetic Chain Research Articles

Acute tetrahydrobiopterin supplementation attenuates sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle of healthy rats.

Tetrahydrobiopterin (BH4) is an essential cofactor for the production of nitric oxide (NO) and supplementation with BH4 improves NO‐dependent vasodilation. NO also reduces sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Thus, we hypothesized that supplementation with BH4 would blunt sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Sprague‐Dawley rats (n = 15, 399 ± 57 g) were anesthetized and instrumented with an indwelling brachial artery catheter, femoral artery flow probe, and a stimulating electrode on the lumbar sympathetic chain. Triceps surae muscles were stimulated to contract rhythmically at 30% and 60% of maximal contractile force (MCF). The percentage change of femoral vascular conductance (%FVC) in response to sympathetic stimulations delivered at 2 and 5 Hz was determined at rest and during muscle contraction in control and acute BH4 supplementation (20 mg·kg−1 + 10 mg·kg−1·h−1, IA) conditions. BH4 reduced (P < 0.05) the vasoconstrictor response to sympathetic stimulation (i.e., decrease in FVC) at rest (Control: 2 Hz: −28 ± 5%FVC; 5 Hz: −45 ± 5%; BH4: 2 Hz: −17 ± 4%FVC; 5 Hz: −34 ± 7%FVC) and during muscular contraction at 30% MCF (Control: 2 Hz: −14 ± 6%FVC; 5 Hz: −28 ± 11%; BH4: 2 Hz: −6 ± 6%FVC; 5 Hz: −16 ± 10%) and 60% MCF (Control: 2 Hz: −7 ± 3%FVC; 5 Hz: −16 ± 6%FVC; BH4: 2 Hz: −2 ± 3%FVC; 5 Hz: −11 ± 6%FVC). These data are consistent with our hypothesis that acute BH4 supplementation decreases sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle.

Effect of hindlimb unloading on sympathetic vasoconstriction in resting and contracting skeletal muscle (1165.3)

We hypothesized that hindlimb unloading (HU) would increase sympathetic vasoconstrictor responsiveness and diminish nitric oxide (NO) mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle. Sprague‐Dawley rats (n=21) were randomized to sedentary time‐control (S; n = 9) or HU (n = 12) groups for 21d. Rats were anesthetized and instrumented for stimulation of the lumbar sympathetic chain and measurement of femoral vascular conductance (FVC). Sympathetic stimulations were delivered at 2Hz and 5Hz at rest and during contraction of the triceps surae muscles at 60% of maximal contractile force before and after NO synthase blockade (L‐NAME; 5mg·kg‐1 IV). The percentage decrease in FVC in response to sympathetic stimulation was not different (P &gt; 0.05) between groups at rest (HU: 2Hz: ‐29 ± 10%; 5Hz: ‐50 ± 12%; S: 2Hz: ‐26 ± 10%, 5Hz: ‐44 ± 8%) and during contraction (HU: 2Hz: ‐9 ± 4%; 5Hz: ‐22 ± 7%; S: 2Hz: ‐7 ± 5%; 5Hz:‐18 ± 7%). In the presence of L‐NAME the vasoconstrictor response was not different (P &gt; 0.05) between groups at rest (HU: 2Hz: ‐43 ± 7%; 5Hz: ‐63 ± 10%; S: 2Hz: ‐42 ± 8%; 5Hz: ‐57 ± 6%) and during contraction (HU: 2Hz: ‐12 ± 3%; 5Hz: ‐24 ± 6%; S: 2Hz: ‐12 ± 4%; 5Hz: ‐28 ± 8%). We conclude that HU does not alter sympathetic vasoconstrictor responsiveness or NO mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle.Grant Funding Source: Supported by NSERC, Canada.

Increased dietary salt intake enhances the exercise pressor reflex

Increased dietary salt in rats has been shown to sensitize central sympathetic circuits and enhance sympathetic responses to several stressors, including hyperinsulinemia, intracerebroventricular injection of angiotensin, and electrical stimulation of sciatic nerve afferents. These findings prompted us to test the hypothesis that increased dietary salt enhanced the exercise pressor reflex. Male Sprague-Dawley rats were fed 0.1% (low) or 4.0% (high) NaCl chow for 2 to 3 wk. On the day of the experiment, the rats were decerebrated, and the hind limb muscles were statically contracted for 30 s by electrically stimulating the cut peripheral ends of the L4 and L5 ventral roots. We found that contraction produced a significantly greater increase in mean arterial pressure of rats fed 4.0% (n = 26) vs. 0.1% (n = 22) NaCl (24 ± 2 vs. 15 ± 2 mmHg, respectively; P < 0.05). Baseline mean arterial pressure was not different between groups (0.1%, 77 ± 4 vs. 4.0% NaCl, 80 ± 3 mmHg). Likewise, the tension time indexes were not different between the two groups (P = 0.42). Section of the L4 and L5 dorsal roots greatly attenuated both the pressor and cardioaccelerator responses to contraction in both groups of rats, an effect showing that the responses were reflex in origin. Finally, electrical stimulation of the lumbar sympathetic chain produced similar increases in mean arterial pressure and decreases in femoral arterial blood flow and conductance between rats fed 0.1% vs. 4.0% NaCl diets. We conclude that increased dietary salt enhances the exercise pressor reflex.

Respiratory, metabolic and cardiac functions are altered by disinhibition of subregions of the medial prefrontal cortex

The prefrontal cortex (PFC) is referred to as the visceral motor cortex; however, little is known about whether this region influences respiratory or metabolic outflows. The aim of this study was to describe simultaneous changes in respiratory, metabolic and cardiovascular functions evoked by disinhibition of the medial PFC (mPFC) and adjacent lateral septal nucleus (LSN). In urethane-anaesthetized rats, bicuculline methiodide was microinjected (2 mm; GABA-A receptor antagonist) into 90 sites in the mPFC at 0.72-4.00 mm from bregma. Phrenic nerve amplitude and frequency, arterial pressure, heart rate, splanchnic and lumbar sympathetic nerve activities (SNA), expired CO2, and core and brown adipose tissue temperatures were measured. Novel findings included disturbances to respiratory rhythm evoked from all subregions of the mPFC. Injections into the cingulate cortex evoked reductions in central respiratory function exclusively, whereas in ventral sites, particularly the infralimbic region, increases in respiratory drive and frequency, and metabolic and cardiac outflows were evoked. Disinhibition of sites in surrounding regions revealed that the LSN could evoke cardiovascular changes accompanied by distinct oscillations in SNA, as well as increases in respiratory amplitude. We show that activation of neurons within the mPFC and LSN influence respiratory, metabolic and cardiac outflows in a site-dependent manner. This study has implications with respect to the altered PFC neuronal activity seen in stress-related and mental health disorders, and suggests how basic physiological systems may be affected.

Short‐term exercise training augments α2‐adrenoreceptor‐mediated sympathetic vasoconstriction in resting and contracting skeletal muscle

We hypothesized that exercise training (ET) would alter α2-adrenoreceptor-mediated sympathetic vasoconstriction. Sprague-Dawley rats (n = 30) were randomized to sedentary (S), mild- (M) or heavy-intensity (H) treadmill ET groups (5 days per week for 4 weeks). Following the ET component of the study, rats were anaesthetized, and instrumented for lumbar sympathetic chain stimulation, triceps surae muscle contraction and measurement of femoral vascular conductance (FVC). The percentage change of FVC in response to sympathetic stimulation was determined at rest and during contraction in control, α2 blockade (yohimbine) and combined α2 + nitric oxide (NO) synthase (NOS) blockade (N-nitro-L-arginine methyl ester hydrochloride, L-NAME) conditions. ET augmented (P < 0.05) sympathetic vasoconstrictor responses at rest and during contraction. Yohimbine reduced (P < 0.05) the vasoconstrictor response in ET rats at rest (M: 2 Hz: 8 ± 2%, 5 Hz: 9 ± 4%; H: 2 Hz: 14 ± 5%, 5 Hz: 11 ± 6%) and during contraction (M: 2 Hz: 9 ± 2%, 5 Hz: 9 ± 5%; H: 2 Hz: 8 ± 3%, 5 Hz: 6 ± 6%) but did not change the response in S rats. The addition of L-NAME caused a larger increase (P < 0.05) in the vasoconstrictor response in ET than in S rats at rest (2 Hz: S: 8 ± 2%, M: 15 ± 3%, H: 23 ± 7%; 5 Hz: S: 8 ± 5%, M: 15 ± 3%, H: 17 ± 5%) and during contraction (2 Hz: S: 9 ± 3%, M: 18 ± 3%, H: 22 ± 6%; 5 Hz: S: 9 ± 5%, M: 22 ± 4%, H:26 ± 9%). Sympatholysis was greater (P < 0.05) in ET than in S rats. Blockade of α2-adrenoreceptors and NOS reduced (P < 0.05) sympatholysis in ET rats, but had no effect on sympatholysis in S rats. In conclusion, ET increased α2-mediated vasoconstriction at rest and during contraction.

A novel approach to the lumbar sympathetic chain: lateral access

Plantar hyperhydrosis is a disabling condition of excessive, symmetric, focal sweating of the feet with social, psychological, and medical implications. Treatment options include topical agents, iontophoresis, botulinum toxin injection, and surgical disruption of the lumbar sympathetic chain. Surgical corridors include transperitoneal and retroperitoneal approaches. We report our technique with a novel minimally invasive lateral retroperitoneal approach commonly used for lateral interbody fusions. The lateral approach for sectioning of the sympathetic chain in the treatment of hyperhydrosis appears safe. The approach may be advantageous for the patient and surgeons familiar with lateral interbody fusion. Further studies may elucidate the long term efficacy and safety of the lateral approach. The video can be found here: http://youtu.be/Q82SGpmAXng.

Role of neuronal nitric oxide in the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle of healthy rats

Isoform-specific nitric oxide (NO) synthase (NOS) contributions to NO-mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle are incompletely understood. The purpose of the present study was to investigate the role of neuronal NOS (nNOS) in the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle of healthy rats. We hypothesized that acute pharmacological inhibition of nNOS would augment sympathetic vasoconstriction in resting and contracting skeletal muscle, demonstrating that nNOS is primarily responsible for NO-mediated inhibition of sympathetic vasoconstriction. Sprague-Dawley rats (n = 13) were anesthetized and instrumented with an indwelling brachial artery catheter, femoral artery flow probe, and lumbar sympathetic chain stimulating electrodes. Triceps surae muscles were stimulated to contract rhythmically at 60% of maximal contractile force. In series 1 (n = 9), the percent change in femoral vascular conductance (%FVC) in response to sympathetic stimulations delivered at 2 and 5 Hz was determined at rest and during muscle contraction before and after selective nNOS blockade with S-methyl-l-thiocitrulline (SMTC, 0.6 mg/kg iv) and subsequent nonselective NOS blockade with N(ω)-nitro-l-arginine methyl ester (l-NAME, 5 mg/kg iv). In series 2 (n = 4), l-NAME was injected first, and then SMTC was injected to determine if the effect of l-NAME on constrictor responses was influenced by selective nNOS inhibition. Sympathetic stimulation decreased FVC at rest (-25 ± 7 and -44 ± 8%FVC at 2 and 5 Hz, respectively) and during contraction (-7 ± 3 and -19 ± 5%FVC at 2 and 5 Hz, respectively). The decrease in FVC in response to sympathetic stimulation was greater in the presence of SMTC at rest (-32 ± 6 and -49 ± 8%FVC at 2 and 5 Hz, respectively) and during contraction (-21 ± 4 and -28 ± 4%FVC at 2 and 5 Hz, respectively). l-NAME further increased (P < 0.05) the sympathetic vasoconstrictor response at rest (-47 ± 4 and -60 ± 6%FVC at 2 and 5 Hz, respectively) and during muscle contraction (-33 ± 3 and -40 ± 6%FVC at 2 and 5 Hz, respectively). The effect of l-NAME was not altered by the order of nNOS inhibition. These data demonstrate that NO derived from nNOS and endothelial NOS contribute to the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle.

Acute superoxide scavenging reduces sympathetic vasoconstrictor responsiveness in short-term exercise-trained rats

We hypothesized that acute superoxide (O2(-)) scavenging would attenuate sympathetic vasoconstrictor responsiveness by augmenting nitric oxide (NO)-mediated inhibition of sympathetic vasoconstriction in exercise-trained rats. Sprague-Dawley rats were randomly assigned to sedentary time control (S; n = 7) or mild- (M: 20 m/min, 5° grade; n = 7) or heavy-intensity (H: 40 m/min, 5° grade; n = 7) exercise training (ET) groups and trained 5 days/wk for 4 wk with matched training volume. Following ET, rats were anesthetized and instrumented for lumbar sympathetic chain stimulation and measurement of femoral vascular conductance. In resting skeletal muscle, the percentage change of femoral vascular conductance in response to continuous (2 Hz) and patterned (20 and 40 Hz) sympathetic stimulation was determined during control conditions, O2(-) scavenging (TIRON, 1 g·kg(-1)·h(-1) iv) and combined O2(-) scavenging + nitric oxide synthase blockade (N(ω)-nitro-l-arginine methyl ester, 5 mg/kg iv). ET augmented the vasoconstrictor response to sympathetic stimulation in a training intensity-dependent manner (P < 0.05) (S: 2 Hz: -26 ± 7.1%; 20 Hz: -26.9 ± 7.3%; 40 Hz: -27.7 ± 7.0%; M: 2 Hz: -37.4 ± 8.3%; 20 Hz: -35.9 ± 7.4%; 40 Hz: -38.2 ± 9.4%; H: 2 Hz: -46.9 ± 7.8%; 20 Hz: -48.5 ± 7.2%; 40 Hz: -51.2 ± 7.3%). O2(-) scavenging did not alter (P > 0.05) the vasoconstrictor response in S rats (S: 2 Hz: -23.9 ± 7.6%; 20 Hz: -26.1 ± 9.1%; 40 Hz: -27.5 ± 7.2%), whereas the response in ET rats was diminished (M: 2 Hz: -26.3 ± 5.1%; 20 Hz: -28.7 ± 5.3%; 40 Hz: -28.5 ± 5.6%; H: 2 Hz: -35.5 ± 10.3%; 20 Hz: -38.6 ± 6.8%; 40 Hz: -43.9 ± 5.9%, P < 0.05). TIRON + N(ω)-nitro-l-arginine methyl ester increased vasoconstrictor responsiveness (P < 0.05) in ET rats (M: 2 Hz: -47.7 ± 9.8%; 20 Hz: -41.2 ± 7.2%; 40 Hz: -50.5 ± 7.9%; H: 2 Hz: -55.8 ± 7.6%; 20 Hz: -55.7 ± 7.8%; 40 Hz: -58.7 ± 6.2%), whereas, in S rats, the response was unchanged (2 Hz: -29.4 ± 8.7%; 20 Hz: -30.0 ± 7.4%; 40 Hz: -35.2 ± 10.3%; P > 0.05). These data indicate that the augmented sympathetic vasoconstrictor responsiveness in ET rats was related to increased oxidative stress and altered nitric oxide-mediated inhibition of vasoconstriction.

Functional sympatholysis (FS) in rats is graded with exercise but is not NO‐mediated

FS is the exercise attenuation of sympathetic vasoconstriction. It is unclear if NO is the major mediator of FS or if the size of FS is graded to the level of exercise. Experiments were performed on anaesthetised rats (under UK legislation). Sympathetic vasoconstriction was induced by stimulation of the lumbar sympathetic chain (LSC). EDL contraction was evoked and tension recorded; femoral vascular resistance (FVR) was calculated. Vasoconstriction was evoked during baseline and graded muscle contraction (10–30% max twitch) under control conditions, after NOS inhibition (L‐NAME) and following restoration of baseline (SNP infusion). LSC‐evoked vasoconstriction (an increase in FVR) was attenuated at all levels of muscle contraction. FS was graded and correlated to the peak force at each level. L‐NAME increased baseline FVR and the vasoconstriction, but had no effect on FS at any level of muscle contraction. SNP restored baseline FVR and the vasoconstriction ‐ FS was similar to control conditions. FS was graded to the peak level of muscle contraction, not the force recorded during the sympathetic stimulation per se. Manipulation of endogenous levels of NO changes the magnitude of sympathetic vasoconstriction but does not alter the extent of FS during any of the muscle contractions used. These results are similar to human studies (no role for NO) but differ from animal studies (role for NO; see Saltin et al, 2012).

Tetrahydrobiopterin attenuates sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle

We tested the hypothesis that acute tetrahydrobiopterin (BH4) supplementation would attenuate sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Sprague‐Dawley rats (n=15) were anesthetised and instrumented for lumbar sympathetic chain stimulation and measurement of arterial blood pressure and femoral artery blood flow. Femoral vascular conductance (FVC) was calculated. The sciatic nerve was stimulated to contract the triceps surae muscle group at 30 and 60% of maximal contractile force (MCF). The percent change in FVC in response to sympathetic stimulation at 2 and 5 Hz was determined at rest and during contraction before and after BH4 (20mg/kg + 10mg/kg/hr IA) supplementation. BH4 blunted (p&lt;0.05) the vascular response to sympathetic stimulation at rest (CONTROL: 2Hz: −28 ± 5%; 5Hz: −45 ± 5%; BH4: 2Hz: −17 ± 4%; 5Hz: −34 ± 7%) and during contraction at 30%MCF (CONTROL: 2Hz: −14 ± 6%; 5Hz: −28 ± 11%; BH4: 2Hz: −6 ± 6%; 5Hz: −16 ± 10%) and 60%MCF (CONTROL: 2Hz: −7 ± 3%; 5Hz: −16 ± 6%; BH4: 2Hz: −3 ± 3%; 5Hz: −11 ± 6%). In conclusion, acute supplementation of the nitric oxide synthase cofactor BH4 reduced the vascular response to sympathetic stimulation in resting and contracting skeletal muscle. These data demonstrate that BH4 supplementation augmented nitric oxide‐mediated inhibition of sympathetic vasoconstriction. NSERC, Canada.

Is functional sympatholysis (FS) altered in chronically hypoxic (CH) rats?

Muscle sympathetic vasoconstriction is blunted in CH, however, there is no change in the modulatory role of NO. Exercise intolerance and CH are features of diseases such as COPD, this may reflect alterations in FS and fatigability. In accordance with UK legislation, experiments were performed on anaesthetised CH rats (3 weeks acclimation to 12% O2). Lumbar sympathetic chain stimulation was used to induce sympathetic vasoconstriction. Peroneal nerve stimulation evoked EDL contraction and tension was recorded. Femoral vascular resistance was calculated from recordings of arterial blood pressure and femoral blood flow. Sympathetic vasoconstriction was evoked during baseline and graded muscle contraction (10–30% max twitch) under control conditions, after NOS inhibition (L‐NAME) and again following restoration of background NO levels (SNP infusion). Compared to normal (N) rats, peak muscle tension was not different but CH rats fatigued more such that plateau tension was lower (even when O2 delivery was similar to N rats). FS was not different in CH and N rats and was not affected by either L‐NAME or SNP infusion. Muscle fatigue is greater in CH than N rats but it is not due to differences in O2 delivery. FS is unchanged despite sympathetic vasoconstriction being blunted in CH rats, and there appears to be no role for NO in mediating FS. Changes in FS are unlikely to explain exercise intolerance in diseases such as COPD.

Short‐term exercise training shifts the control of sympathetic vasoconstriction in contracting skeletal muscle to the α2‐adrenergic receptor

We hypothesized that short‐term mild‐ (M) and heavy‐intensity (H) exercise training (ET) would augment α2‐adrenergic receptor mediated vasoconstriction in skeletal muscle. Sprague‐Dawley rats (n=30) were randomized to sedentary (S), M (20m/min5% grade) or H (40m/min5% grade) ET groups and trained 5d/wk for 4 wks with equal ET volume. Rats were anesthetised and instrumented for lumbar sympathetic chain stimulation and measurement of femoral vascular conductance (FVC). Triceps surae muscles were contracted at 60% of maximal contractile force. The percent decrease in FVC to sympathetic stimulation (2 and 5 Hz) was determined at rest and during contraction before (C) and after α2 blockade (Yohimbine; Y). ET increased (p&lt;0.05) vasoconstrictor responsiveness. Y did not alter (p&gt;;0.05) the decrease in FVC in S rats at rest (C: 2Hz: −22±5% 5Hz: −36±6%; Y: 2Hz: −20±5% 5Hz: −34±6%) or during contraction (C: 2Hz: −6±4% 5Hz: −18±5%; Y: 2Hz: −7±3% 5Hz: −16±5%). In contrast, Y reduced (p&lt;0.05) vasoconstriction in ET rats at rest (M: C: 2Hz: −34±4% 5Hz: −47±7%; Y: 2Hz: −26±5% 5Hz: −38±7%; H: C: 2Hz: −44±5% 5Hz: −57±8%; Y: 2Hz: −30±6% 5Hz: −46±6%) and during contraction (M: C: 2Hz: −12±3% 5Hz: −20±3%; Y: 2Hz: −3±2% 5Hz: −11±5%; H: C: 2Hz: −12±3% 5Hz: −19±7%; Y: 2Hz: −4±3% 5Hz: −12±2%). ET increased α2 mediated constriction and shifted the control of sympathetic vasoconstriction in contracting muscle to the α2 receptor. NSERC, Canada.

Short‐term exercise training enhances functional sympatholysis through a nitric oxide‐dependent mechanism

We tested the hypothesis that short-term mild- (M) and heavy-intensity (H) exercise training would enhance sympatholysis through a nitric oxide (NO)-dependent mechanism. Sprague-Dawley rats (n = 36) were randomly assigned to sedentary (S) or to M (20 m min(-1) 5% gradient) or H exercise training groups (40 m min(-1) 5% gradient). Rats assigned to M and H groups trained on 5 days week(-1) for 4 weeks, with the volume of training being matched between groups. Rats were anaesthetized and instrumented for stimulation of the lumbar sympathetic chain and the measurement of arterial blood pressure and femoral artery blood flow. The triceps surae muscle group was stimulated to contract rhythmically at 30 and 60% of maximal contractile force (MCF). The percentage change of femoral vascular conductance (%FVC) in response to sympathetic stimulation delivered at 2 and 5 Hz was determined at rest and during contraction at 30 and 60% MCF. The vascular response to sympathetic stimulation was reduced as a function of MCF in all rats (P < 0.05). At 30% MCF, the magnitude of sympatholysis (%FVC rest - contraction; %FVC) was greater in H compared with M and S groups (%FVC at 2 Hz, S, 9 ± 5; M, 11 ± 8; and H, 18 ± 7; and %FVC at 5 Hz, S, 6 ± 6; M, 12 ± 9; and H, 18 ± 7; P < 0.05) and was greater in H and M compared with S at 60% MCF (%FVC at 2 Hz, S, 15 ± 5; M, 25 ± 3; and H, 36 ± 6; and %FVC at 5 Hz, S, 22 ± 6; M, 33 ± 9; and H, 39 ± 9; P < 0.05). Blockade of NO synthase did not alter the magnitude of sympatholysis in S during contraction at 30 or 60% MCF. In contrast, NO synthase inhibition diminished sympatholysis in H at 30% MCF and in M and H at 60% MCF (P < 0.05). The present findings indicate that short-term exercise training augments sympatholysis in a training-intensity-dependent manner and through an NO-dependent mechanism.

Dorsal root ganglion neurons innervating pelvic organs in the mouse express tyrosine hydroxylase

Previous studies in rat and mouse documented that a subpopulation of dorsal root ganglion (DRG) neurons innervating non-visceral tissues express tyrosine hydroxylase (TH). Here we studied whether or not mouse DRG neurons retrogradely traced with Fast Blue (FB) from colorectum or urinary bladder also express immunohistochemically detectable TH. The lumbar sympathetic chain (LSC) and major pelvic ganglion (MPG) were included in the analysis. Previously characterized antibodies against TH, norepinephrine transporter type 1 (NET-1) and calcitonin gene-related peptide (CGRP) were used. On average, ∼14% of colorectal and ∼17% of urinary bladder DRG neurons expressed TH and spanned virtually all neuronal sizes, although more often in the medium-sized to small ranges. Also, they were more abundant in lumbosacral than thoracolumbar DRGs, and often coexpressed CGRP. We also detected several TH-immunoreactive (IR) colorectal and urinary bladder neurons in the LSC and the MPG, more frequently in the former. No NET-1-IR neurons were detected in DRGs, whereas the majority of FB-labeled, TH-IR neurons in the LSC and MPG coexpressed this marker (as did most other TH-IR neurons not labeled from the target organs). TH-IR nerve fibers were detected in all layers of the colorectum and the urinary bladder, with some also reaching the basal mucosal cells. Most TH-IR fibers in these organs lacked CGRP. Taken together, we show: (1) that a previously undescribed population of colorectal and urinary bladder DRG neurons expresses TH, often CGRP but not NET-1, suggesting the absence of a noradrenergic phenotype; and (2) that TH-IR axons/terminals in the colon or urinary bladder, naturally expected to derive from autonomic sources, could also originate from sensory neurons.

Short-term exercise training augments sympathetic vasoconstrictor responsiveness and endothelium-dependent vasodilation in resting skeletal muscle

We tested the hypotheses that 4 wk of exercise training would diminish the magnitude of vasoconstriction in response to sympathetic nerve stimulation and augment endothelium-dependent vasodilation (EDD) in resting skeletal muscle in a training intensity-dependent manner. Sprague-Dawley rats were randomly assigned to sedentary time-control (S), mild- (M; 20 m/min, 5% grade), or heavy-intensity (H; 40 m/min, 5% grade) treadmill exercise groups. Animals trained 5 days/wk for 4 wk with training volume matched between groups. Rats were anesthetized and instrumented for study 24 h after the last training session. Arterial pressure and femoral artery blood flow were measured, and femoral vascular conductance (FVC) was calculated. Lumbar sympathetic chain stimulation was delivered continuously at 2 Hz and in patterns at 20 and 40 Hz. EDD was assessed by the vascular response to intra-arterial bolus injections of ACh. The response (% change FVC) to sympathetic stimulation increased (P < 0.05) in a training intensity-dependent manner at 2 Hz (S: -20.2 ± 9.8%, M: -34.0 ± 6.7%, and H: -44.9 ± 2.0%), 20 Hz (S: -22.0 ± 10.6%, M: -31.2 ± 8.4%, and H: -42.8 ± 5.9%), and 40 Hz (S: H -24.5 ± 8.5%, M: -35.1 ± 8.9%, H: -44.9 ± 6.5%). The magnitude of EDD also increased in a training intensity-dependent manner (P < 0.05). These data demonstrate that short-term exercise training augments the magnitude of vasoconstriction in response to sympathetic stimulation and EDD in resting skeletal muscle in a training intensity-dependent manner.

Comparison of Complications of Anterolateral and Lateral TransPsoatic Retroperitoneal Approaches to the Th12-L5 Intervertebral Disks. Experience with 208 Patients

Introduction Anterior lumbar interbody fusion using supportive cage is a common surgical method for treating degenerative lumbar spinal diseases. Improved surgical techniques and better results have led to renewed interest in this procedure and to the development of new lateral transPsoatic minimally invasive access to the lumbar disks. The aim of this study was to compare the rate of complications during traditional anterolateral and new lateral transPsoatic retroperitoneal approaches to the intervertebral disks (IVD) at levels Th12-L5. Materials and Methods We reviewed all cases of the IVD anterolateral and lateral surgery at level Th12-L5, treated at the Department of Neurosurgery from January 1996 to June 2011. The ALIF (Anterior Lumbar Interbody Fusion) group consisted of 120 patients: 53 women and 67 men, average age 44 years, range 17 to 76 years; and the XLIF (Extreme Lateral Interbody Fusion) group consisted of 88 patients: 50 women and 38 men, average age 51 years, range 17 to 74 years. They suffered from low back pain (LBP) and usually radiculopathy itself and conservative treatment was not effective for a minimum of 6 months. The diagnosis was established using generally accepted methods including history-taking and physical examination, radiography, and magnetic resonance imaging (MRI) of the lumbosacral (LS) spine. The preoperative diagnosis of ALIF group was degenerative disk disease at 39 levels, failed back surgery syndrome (FBSS) at 27, spondylolisthesis at 27, and posttraumatic disk injury at 35 levels. The preoperative diagnosis of XLIF group was DDD at 39, FBSS at 22, spondylolisthesis at 17, retrolisthesis at 5, and posttraumatic disk injury at 9 levels. The whole surgery, including surgical approach in the lateral decubitus position, was performed by an experienced neurosurgical team. The surgical steps in the minimally invasive anterolateral retroperitoneal approach and lateral retroperitoneal transPsoatic approach from the left side to disks Th12-L5 are described. Intraoperatively during XLIF procedure, the surgeon identified the lumbar nerve roots with stimulator to prevent their injury. All surgical intraoperative and postoperative complications directly related to the spinal surgery were documented. Both study groups were compared to each other. Results In both the groups, we had no serious complications such as death, excessive intra- or postoperative bleeding, thromboembolism, infection, visceral injury, injury of ureter or kidney, ileus, retrograde ejaculation, or sterility. In ALIF group, intra- and postoperative minor complications were found in 35 patients (29%), the main intraoperative complication was the necessity to perform sympathectomy of lumbar sympathetic chain to obtain wide access to the disks in 19 patients (16%). For all of these patients with symptoms of sympathectomy the thermography was done as a sensitive test. The main postoperative complications were numbness of left anterolateral thigh or groin or transient pain of left groin in 16 patients (13%). In XLIF group, we had partial and transient injury of L5 nerve root (just the first patient) during implant insertion at level L4/5 (one patient, 1%), without using an intraoperative neuromonitoring (IOM). Since this major complication, we started using IOM strictly and didnát have more nerve injuries. In XLIF group, intra- and postoperative minor complications were found in 20 patients (23%), mainly transient pain of left groin in 11 patients and sympathectomy in 4 patients. At follow-up, we found no hardware failure on X-ray (implant displacement). Total 198 patients were satisfied with the surgery and reported improvement, 10 patients were neither improved nor worsened. Conclusion Rate of minor complications was similar in both groups, in ALIF group 29% and in XLIF group 23% of treated patients. Only one major complication, nerve root injury, was due to underestimation of XLIF procedure in the beginning. Retroperitoneal access and surgery at levels Th12-L5 disk space is a safe procedure when performed by a knowledgeable and experienced spine team. IOM during XLIF surgery is fully recommended. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Crock HV. Anterior lumbar interbody fusion: indications for its use and notes on surgical technique. Clinical Orthopaedics 1982;165:157–163 Faciszewski T, Winter RB, Lonstein JE, Denis F, Johnson L. The surgical and medical perioperative complications of anterior spinal fusion surgery in the thoracic and lumbar spine in adults. Spine 1995;20:1592–1599 Mayer HM. A new microsurgical technique for minimally invasive anterior lumbar interbody fusion. Spine 1997;22:691–700 Mehren C, Mayer HM, Siepe C, Grochulla F, Korge A. The minimally invasive anterolateral approach to L2-5. Oper Orthop Traumatol 2010;22:221–228 Zdeblick TA, David SM. A prospective comparison of surgical approach for anterior L4-L5 fusion. Spine 2000;25:2682–2687

Short‐term exercise training enhances nitric oxide‐mediated sympatholysis

We hypothesized that exercise training (ET) would enhance nitric oxide (NO)‐mediated inhibition of sympathetic vasoconstriction in contracting skeletal muscle. Sprague‐dawley rats (n=36) were randomly assigned to sedentary (S), mild‐ (M: 20m/min5% grade) or heavy‐intensity ET groups (H: 40m/min5% grade) and trained 5d/wk for 4 wks with the volume of ET matched. Rats were anesthetised and instrumented for stimulation of the lumbar sympathetic chain and the measurement of arterial blood pressure and femoral artery blood flow. The triceps surae muscles were stimulated to contract at 30 and 60% of maximal contractile force (MCF). The percent change in femoral vascular conductance (%FVC) in response to sympathetic chain stimulation (2 and 5 Hz) was determined at rest and during contractions before and after NO synthase (NOS) blockade. The magnitude of sympatholysis (%FVC rest – contraction) was greater in H compared to M and S at 30% MCF (2Hz‐ S: 9±5, M: 11±8, H: 18±7; 5Hz‐ S: 6±6, M: 12±9, H: 18±7; p&lt;0.05) and was greater in H and M compared to S at 60% MCF (2Hz‐ S: 15±5; M: 25±3; H: 36±6; 5Hz‐ S: 22±6; M: 33±9; H: 39±9; p&lt;0.05). NOS blockade did not alter the magnitude of sympatholysis in S during contraction at 30 or 60% MCF. In contrast, sympatholysis was diminished in H at 30% MCF and M and H at 60% MCF by NOS inhibition. These data demonstrate that short‐term ET augments sympatholysis through an NO‐mediated mechanism. NSERC Canada.

Expression of vesicular glutamate transporters type 1 and 2 in sensory and autonomic neurons innervating the mouse colorectum

Vesicular glutamate transporters (VGLUTs) have been extensively studied in various neuronal systems, but their expression in visceral sensory and autonomic neurons remains to be analyzed in detail. Here we studied VGLUTs type 1 and 2 (VGLUT(1) and VGLUT(2) , respectively) in neurons innervating the mouse colorectum. Lumbosacral and thoracolumbar dorsal root ganglion (DRG), lumbar sympathetic chain (LSC), and major pelvic ganglion (MPG) neurons innervating the colorectum of BALB/C mice were retrogradely traced with Fast Blue, dissected, and processed for immunohistochemistry. Tissue from additional naïve mice was included. Previously characterized antibodies against VGLUT(1) , VGLUT(2) , and calcitonin gene-related peptide (CGRP) were used. Riboprobe in situ hybridization, using probes against VGLUT(1) and VGLUT(2) , was also performed. Most colorectal DRG neurons expressed VGLUT(2) and often colocalized with CGRP. A smaller percentage of neurons expressed VGLUT(1) . VGLUT(2) -immunoreactive (IR) neurons in the MPG were rare. Abundant VGLUT(2) -IR nerves were detected in all layers of the colorectum; VGLUT(1) -IR nerves were sparse. A subpopulation of myenteric plexus neurons expressed VGLUT2 protein and mRNA, but VGLUT1 mRNA was undetectable. In conclusion, we show 1) that most colorectal DRG neurons express VGLUT(2) , and to a lesser extent, VGLUT(1) ; 2) abundance of VGLUT2-IR fibers innervating colorectum; and 3) a subpopulation of myenteric plexus neurons expressing VGLUT(2). Altogether, our data suggests a role for VGLUT(2) in colorectal glutamatergic neurotransmission, potentially influencing colorectal sensitivity and motility.

Some lumbar sympathetic neurons develop a glutamatergic phenotype after peripheral axotomy with a note on VGLUT 2-positive perineuronal baskets

Glutamate is the main excitatory neurotransmitter in the nervous system, including in primary afferent neurons. However, to date a glutamatergic phenotype of autonomic neurons has not been described. Therefore, we explored the expression of vesicular glutamate transporter (VGLUT) types 1, 2 and 3 in lumbar sympathetic chain (LSC) and major pelvic ganglion (MPG) of naïve BALB/C mice, as well as after pelvic nerve axotomy (PNA), using immunohistochemistry and in situ hybridization. Colocalization with activating transcription factor-3 (ATF-3), tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT) and calcitonin gene-related peptide was also examined. Sham-PNA, sciatic nerve axotomy (SNA) or naïve mice were included. In naïve mice, VGLUT 2-like immunoreactivity (LI) was only detected in fibers and varicosities in LSC and MPG; no ATF-3-immunoreactive (IR) neurons were visible. In contrast, PNA induced upregulation of VGLUT 2 protein and transcript, as well as of ATF-3-LI in subpopulations of LSC neurons. Interestingly, VGLUT 2-IR LSC neurons coexpressed ATF-3, and often lacked the noradrenergic marker TH. SNA only increased VGLUT 2 protein and transcript in scattered LSC neurons. Neither PNA nor SNA upregulated VGLUT 2 in MPG neurons. We also found perineuronal baskets immunoreactive either for VGLUT 2 or the acetylcholinergic marker VAChT in non-PNA MPGs, usually around TH-IR neurons. VGLUT 1-LI was restricted to some varicosities in MPGs, was absent in LSCs, and remained largely unaffected by PNA or SNA. This was confirmed by the lack of expression of VGLUT 1 or VGLUT 3 mRNAs in LSCs, even after PNA or SNA. Taken together, axotomy of visceral and non-visceral nerves results in a glutamatergic phenotype of some LSC neurons. In addition, we show previously non-described MPG perineuronal glutamatergic baskets.

The effect of short‐term exercise training on the skeletal muscle vascular response to sympathetic stimulation

The effect of 4 weeks of exercise training (ET) on skeletal muscle sympathetic vasoconstriction was investigated. It was hypothesized that vascular responsiveness to sympathetic stimulation would be increased following ET. Sprague-dawley rats were randomly assigned to sedentary (S: n=12), mild- (M: 20m.min−15% grade; n=13) or heavy-intensity (H: 40m.min−15% grade, n=8) ET groups. Rats were trained 5d.week−1 for 4 weeks with total training volume matched between ET groups. Rats were anesthetised and instrumented with indwelling catheters and a femoral artery flow probe. The vascular response to lumbar sympathetic chain stimulation delivered continuously at 2Hz or in patterns at 20 or 40Hz was determined. The change in femoral vascular resistance (FVR) was calculated and expressed in arbitrary resistance units (RU). Basal blood flow (S: 4±1, M: 3±1, H: 4±1 mL·min−1), MAP (S: 100±14, M: 90±14, H: 89±15 mmHg) and FVR (S: 33±15, M: 27±5, H: 25±7 mmHg.mL·min−1) were similar between groups (p>0.05). Lumbar chain stimulations produced a smaller (p<0.05) increase in FVR at all frequencies in S (2Hz: 7±3; 20Hz: 9±4; 40Hz: 11±5 RU) compared to M (2Hz: 14±4; 20Hz: 18±4; 40Hz: 18±6 RU) and H (2Hz: 21±4; 20Hz: 27±6; 40Hz: 28±4 RU). These data demonstrate that following ET, the vascular response to sympathetic stimulation was up-regulated in a manner dependent on the intensity of training stimulus. NSERC Canada.