The influence of visceral mechanoreceptors on sympathetic efferent discharge in the cat

Changes in Autonomic Nervous System Activity in Children With Spina Bifida: A Case-Control Study

PURPOSE

We compared heart rate variability parameters between patients with spina bifida and a control group during urodynamic studies, with the goal of evaluating the autonomic nervous system dysfunction present in spina bifida.

METHODS

Continuous heart rate variability parameters were recorded during 3 successive periods (P0, the 2 minutes prior to the start of filling; P1, from the start of filling to the first desire to void; and P2, from P1 to the end of filling or the start of voiding). The control group consisted of children with vesicoureteral reflux who had undergone video-urodynamic studies. Our study included 11 patients with spina bifida and 9 control participants.

RESULTS

At baseline, patients with spina bifida exhibited lower values for the root mean square of successive differences in NN intervals, the percentage of successive R-R interval differences exceeding 50 msec relative to the total number of intervals, and high frequency (HF). In contrast, the low frequency (LF)/HF ratio was elevated in these patients (5.04 ± 4.75 vs. 0.67 ± 0.42, P = 0.014). During bladder filling, LF/HF values increased in the control group (P0, 0.67 ± 0.42; P1, 0.89 ± 0.34; P2, 1.21 ± 0.64; P = 0.018), while they declined in patients with spina bifida (P0, 5.04 ± 4.75; P1, 3.96 ± 4.35; P2, 3.26 ± 4.03; P < 0.001). The HF values were significantly elevated in children with spina bifida during bladder filling (P = 0.002). In the time domain, the standard deviations of all NN intervals were elevated only in the control group during bladder filling. Parasympathetic activity domains were reduced in the children with spina bifida at the initial assessment.

CONCLUSION

During the bladder filling phase, parasympathetic activity increased along with fixed sympathetic activity in the spina bifida group. In contrast, the control group exhibited a shift towards a sympathetic preponderance at the conclusion of bladder filling. These observations may be associated with the pathophysiology of neurogenic bladder in spina bifida.

Pathogenic insights from genetic causes of autoinflammatory inflammasomopathies and interferonopathies

A number of systemic autoinflammatory diseases arise from gain-of-function mutations in genes encoding IL-1-activating inflammasomes or cytoplasmic nucleic acid sensors including the receptor and sensor STING and result in increased IL-1 and type I interferon production, respectively. Blocking these pathways in human diseases has provided proof-of-concept, confirming the prominent roles of these cytokines in disease pathogenesis. Recent insights into the multilayered regulation of these sensor pathways and insights into their role in amplifying the disease pathogenesis of monogenic and complex genetic diseases spurred new drug development targeting the sensors. This review provides insights into the pathogenesis and genetic causes of these "prototypic" diseases caused by gain-of function mutations in IL-1-activating inflammasomes (inflammasomopathies) and in interferon-activating pathways (interferonopathies) including STING-associated vasculopathy with onset in infancy, Aicardi-Goutieres syndrome, and proteasome-associated autoinflammatory syndromes that link activation of the viral sensors STING, "self" nucleic acid metabolism, and the ubiquitin-proteasome system to "type I interferon production" and human diseases. Clinical responses and biomarker changes to Janus kinase inhibitors confirm a role of interferons, and a growing number of diseases with "interferon signatures" unveil extensive cross-talk between major inflammatory pathways. Understanding these interactions promises new tools in tackling the significant clinical challenges in treating patients with these conditions.

Autonomic response during bladder hydrodistention reflects the severity of symptoms in patients with bladder pain syndrome/interstitial cystitis

AIMS

To evaluate the correlation between symptom severity of bladder pain syndrome/interstitial cystitis (BPS/IC) and autonomic nervous system activity, we examined autonomic responses during bladder hydrodistention.

METHODS

Medical records were collected from a prospective database for patients who underwent bladder hydrodistention with a fixed protocol from March 2012 to December 2013. A total of 40 patients (16 males, 24 females) were included for the analysis. Hydrodistention was performed under general anesthesia (31 patients), spinal anesthesia (six patients), and both types of anesthesia (three patients) at different times. Twenty-five patients who underwent holmium laser enucleation of the prostate served as controls. Pulse rate (PR), systolic (SBP), and diastolic blood pressure (BP) were measured pre-hydrodistention, during hydrodistention, and after drainage.

RESULTS

The spinal anesthesia and control groups exhibited little change in BP and PR during hydrodistention, while a significant increase was demonstrated in the general anesthesia group (e.g., ΔSBP 4.89 ± 4.80, 10.40 ± 19.03, and 56.26 ± 30.38 mm Hg, respectively, P < 0.001). Under general anesthesia, autonomic response during hydrodistention was more prominent in patients with preoperative visual analogue scale (VAS) pain score ≥7, Hunner's lesion, and glomerulation grade 4. Preoperative maximal cystometric capacity negatively correlated with changes in SBP during hydrodistention (R²  = 0.294, P = 0.009), while VAS score and interstitial cystitis problem index demonstrated a positive correlation with the changes (R²  = 0.208, P = 0.012; R²  = 0.173, P = 0.015).

CONCLUSIONS

Under general anesthesia, exaggerated autonomic responses to bladder hydrodistention were demonstrated in BPS/IC patients, which reflected the severity of symptoms. These results support the hypothesis of altered activity of autonomic system in BPS/IC. Neurourol. Urodynam. 36:677-682, 2017. © 2016 Wiley Periodicals, Inc.

Do the urinary bladder and large bowel interact, in sickness or in health? ICI-RS 2011

Normal functioning of the urinary bladder and the distal gut is an essential part of daily physiological activity coordinated by the peripheral and central nervous systems. Pathological changes in one of these organs may induce the development of cross-organ sensitization in the pelvis and underlie clinical co-morbidity of genitourinary and GI dysfunctions. Experimental human and animal data suggest that the bladder and distal colon interact under both normal and pathological conditions, however, the directions of these interactions can change dramatically depending on the nature and duration of the applied stimuli. This review article aimed to summarize the clinical data on colon-bladder cross-reflexes in healthy individuals, as well as in patients with co-morbid disorders. It also discusses currently used animal models, experimental approaches, and suggested mechanisms of colon-bladder cross-talk. Additionally, it provides an overview of the potential pharmacological targets to develop treatment options for patients with co-morbid disorders. Presented work resulted from the discussion of colon/bladder interactions during "Think Tank 9" presentations at the International Consultation on Incontinence Research Society meeting held in Bristol, UK, 2011.

Neurophysiology of the lower urinary tract

The lower urinary tract (LUT) has two functions: (1) the storage of waste products in the form of urine and (2) the elimination of those wastes through micturition. The LUT operates in a simple "on-off" fashion, either storing urine or releasing it during voiding. While this activity may seem simple, micturition is controlled by a complex set of peripheral neurons that are, in turn, coordinated by cell groups in the spinal cord, brainstem, and brain. When this careful coordination is interrupted, the control of the bladder is lost, resulting in incontinence or retention of urine. The purpose of this chapter is to review how the neural systems coordinating the activity of the lower urinary tract form neural circuits that are responsible for either maintaining continence (the storage reflex) or inducing micturition (the voiding reflex). We will also discuss the brain centers that enable higher organisms to voluntarily choose the time and place for voiding. Finally, we will discuss how defects in the pathways controlling micturition can lead to urinary incontinence and which treatments may normalize LUT function.

Analysis of the afferent limb of the vesicovascular reflex using neurotoxins, resiniferatoxin and capsaicin

The afferent limb of the vesicovascular reflex (VV-R) evoked by distension or contraction of the urinary bladder (UB) was studied in urethane-anesthetized female rats by examining the changes in VV-R after administration of C-fiber afferent neurotoxins [capsaicin and resiniferatoxin (RTX)]. Systemic arterial blood pressure increased parallel (5.1 to 53.7 mmHg) with graded increases in UB pressure (20 to 80 cm H(2)O) or during UB contractions. The arterial pressor response to UB distension was significantly reduced (60-85%) by acute or chronic (4 days earlier) intravesical administration of RTX (100-1,000 nM) or by capsaicin (125 mg/kg sc) pretreatment (4 days earlier). Chronic neurotoxin treatments also increased the volume threshold (>100%) for eliciting micturition in anesthetized rats but did not change voiding pressure. Acute RTX treatment (10-50 nM) did not alter the arterial pressor response during reflex UB contractions, whereas higher concentrations of RTX (100-1,000 nM) blocked reflex bladder contractions. It is concluded that VV-R is triggered primarily by distension- and contraction-sensitive C-fiber afferents located, respectively, near the luminal surface and deeper in the muscle layers of the bladder.

Reduction in renal haemodynamics by exaggerated vesicovascular reflex in rats with acute urinary retention

1. We examined the possibility that a vesicovascular reflex is exaggerated by acute urinary retention, and that the increase in renal vascular resistance caused by this reflex may lead to renal dysfunction. We evaluated the vesicovascular responses to normal micturition (NM, transcystometric condition) and acute urinary retention (isovolumetric condition mimicking complete bladder-outlet obstruction (CBOO) and partial urethral ligation mimicking partial bladder-outlet obstruction (PBOO)) in anaesthetized female Wistar rats. 2. Acute urinary retention due to CBOO or PBOO provoked a prolonged or increased intravesical pressure, an enhancement in both bladder pelvic afferent and bladder pelvic efferent nervous activity, and an elevation in mean arterial blood pressure. 3. Single-unit analysis showed that these vesicovascular reflexes were triggered by activation of low-threshold and high-threshold bladder mechanoreceptors, but not by renal uretropelvic mechanoreceptors. 4. Bladder contraction in CBOO and PBOO conditions and graded increases in bladder volume significantly reduced renal blood flow and cortical microvascular blood flow. The acute urinary retention-induced renal vasoconstriction was mediated by the renal nerve. Renal denervation, but not bilateral ureteral resection, abolished the renal vasoconstriction associated with the vesicovascular reflexes. 5. These findings indicate that exaggerated activation of bladder afferents exerts a positive feedback effect to increase sympathetic outflow to the kidney further, thereby contributing to significant renal vasoconstriction via a renal nerve-dependent mechanism.

Stomach distension increases efferent muscle sympathetic nerve activity and blood pressure in healthy humans

Although the enteric nervous system is usually described as a separate and independent entity, animal studies show that gastric distension causes a reflex increase in arterial pressure and a sympathetically mediated increase in heart rate and peripheral vascular resistance. To assess the influence of gastric distension on sympathetic outflow and blood pressure, we recorded muscle sympathetic nerve activity (MSNA) from the peroneal nerve by microneurography in eight healthy volunteers. The stomach was distended by means of a barostat, using a single staircase protocol by which pressure was increased by 2 mmHg every 3 min. Gastric sensory function was assessed at each distension step by using a visual analog scale (VAS) for sensations of fullness, nausea and pain. For comparison, we also performed a cold pressor test. The MSNA increased on barostat-induced gastric distension with an almost concomitant elevation of blood pressure. The increase in both was proportional to the intragastric pressure and both decreased towards initial values after the end of distension. Heart rate increased inconsistently and only at higher distension pressures that were associated with high VAS scores. The opposite was found for the cold pressor test. The results of this study confirm the existence of a functional relationship between gastrointestinal distension and cardiovascular function. Decrease in this gastrovascular response may play a role in postprandial hypotension in the elderly, since the MSNA responses to simulated microgravity decrease with age.

Gender, bladder distension and hypogastric nerve activity in the cat

In the pentobarbitone anaesthetised cat, postganglionic activity was recorded from the whole hypogastric nerve and from hypogastric filaments destined for the bladder wall during bladder distension. A gender difference was observed in whole hypogastric nerve recordings, cardiac-related activity obscuring other components in females with intact internal reproductive organs. In contrast, nerve activity in the vesical hypogastric filaments was dominated by bladder distension-related activity in both sexes. These observations suggest that bladder distension-related activity, which has a continence promoting action on the bladder detrusor muscle, is destined for the bladder wall, while the cardiac-related activity is largely destined for the uterine and vaginal vasculature.

The pathophysiology of contractile activity in the chronic decentralized feline bladder

Autonomous wave activity occurs in the decentralized bladder and may contribute to upper tract damage and incontinence. In order to clarify the poorly understood pathophysiology and neuropharmacology of autonomous waves, cats were prepared with L7-S3 ventrodorsal rhizotomy alone or with L7-S3 ventral rhizotomy with and without total sympathectomy. The incidence of autonomous waves was < 15% 12 weeks after ventral or ventrodorsal rhizotomy, but acute sympathectomy at 13 weeks increased the incidence to 58% in these groups. With chronic sympathectomy the incidence was 100%. This suggests that the waves arise locally via a mechanism which is independent of L7-S3 dorsal roots, due to lack of a suppressive sympathetic pathway. Autonomous waves were inhibited by atropine after acute sympathectomy and by prazosin after chronic sympathectomy, but increased inhibition occurred after both drugs in either case. Adrenergic neuron depletion with 6-hydroxydopamine enhanced wave activity, which was incompletely inhibited by subsequent atropine. This implies that the peripheral reflex pathway has facilitatory alpha 1-adrenergic, muscarinic and also noncholinergic nonadrenergic elements. Clinically, sensory or sympathetic damage caused incontinence, but sympathectomy also caused high pressure waves, which may cause upper tract damage and treatment resistant incontinence in patients.

Hypogastric nerve section reveals a role for both afferent and efferent fibres in the feline continence process

The role of the hypogastric afferent and efferent innervation in the process of urine storage during natural rate filling was examined in the pentobarbitone anaesthetized cat. The observed changes in bladder pressure following hypogastric nerve section demonstrated the presence of baseline sympatho-inhibitory and phasic sympatho-excitatory influences for a significant portion of each distension, which proceeded to a volume just over halfway through the continence process. A reduction in bladder wall compliance at the end of the distensions provided evidence for a net sympatho-inhibitory influence in the second half of the continence phase. Hypogastric nerve section also resulted in a reduction in the reflex increase in hypogastric efferent nerve activity, measured in-continuity. This suggested that hypogastric afferent fibres made a significant contribution to the regulation of sympathetic hypogastric nerve activity during natural rate filling.

Rate of bladder distension and hypogastric nerve activity in the cat

The effect of two rates of bladder filling on hypogastric efferent nerve activity was examined in cats anaesthetised with a continuous pentobarbitone infusion. At each level of bladder pressure the amount of hypogastric efferent nerve activity was less at the higher filling rate. This result may reflect a volume effect absent in pressure-nerve activity relationships. When volume effects were allowed for, variation in filling rate appeared to have little influence on hypogastric nerve activity.

Differentiation of sympathetic neurones projecting in the hypogastric nerves in terms of their discharge patterns in cats

1. Sympathetic neurones that project in the hypogastric nerves (HGNs) were analysed for their discharge patterns in anaesthetized cats. The activity of these neurones was recorded from their axons. Afferents from the pelvic organs (urinary bladder, colon, anal canal), and arterial baro-and chemoreceptors were stimulated. 150 postganglionic and nine preganglionic neurones were analysed. 2. The postganglionic neurones exhibited reflex patterns that were typical of visceral vasoconstrictor neurones and various types of motility-regulating neurones. Most motility-regulating neurones and all visceral vasoconstrictor neurones had ongoing activity. 3. Postganglionic motility-regulating neurones were not influenced by stimulation of arterial baro-and chemoreceptors, but showed distinctive reflexes on stimulation of afferents from pelvic organs. Three subgroups of motility-regulating neurones were identified: type 1 neurones (34% of the sample of postganglionic neurones) were excited from the urinary bladder and inhibited or not influenced from the colon. Type 2 neurones (14%) exhibited a reflex pattern reciprocal to that of the type 1 neurones. Anal motility-regulating neurones (8%) were only influenced from the anal canal. The most powerful reflexes in these types of motility-regulating neurones were elicited by mechanical stimulation of the anal mucosa. 4. Postganglionic visceral vasoconstrictor neurones (16% of the sample) were under powerful inhibitory control from the arterial baroreceptors and weakly excited by stimulation of arterial chemoreceptors. Visceral stimuli had little or no effect on most of these neurones. Some visceral vasoconstrictor neurones exhibited some overlap in their functional properties with motility-regulating neurones. 5. Twenty-eight per cent of our sample of postganglionic neurones showed no reflexes to the afferent stimuli used. About half of these neurones had on-going activity. 6. Nine preganglionic neurones with on-going activity were identified. Most of these neurones behaved like visceral vasoconstrictor or motility-regulating neurones. 7. This study shows that the majority of postganglionic neurones that project in the HGNs can be divided into the same functional types as the lumbar preganglionic neurones that project to the inferior mesenteric ganglion. The proportions of the different types of neurones are similar at pre- and postganglionic levels. Thus the centrally generated patterns of activity are most likely faithfully transmitted from the spinal cord to the target organs in the pelvic cavity in functionally separate pathways.

Sympathetic activity and blood pressure increases with bladder distension in humans

Microneurographic recordings of muscle nerve sympathetic activity, which is governed by baroreceptors and involved in blood pressure regulation, were made in the peroneal nerve in 16 healthy volunteers during physiological bladder distension. When the urge to urinate was pronounced, sympathetic outflow increased from a baseline level of 16.3 +/- 1.7 to 23.2 +/- 1.9 bursts/min (mean +/- SEM, p less than 0.01). There was a concomitant significant rise in both systolic and diastolic blood pressure, from 125 +/- 2/74 +/- 2 to 140 +/- 4/84 +/- 3 mm Hg. After micturition, sympathetic activity and blood pressure returned toward initial values. It is concluded that 1) increased sympathetic outflow contributed to the rise in blood pressure, 2) there is a vesicovascular response mediated by sympathetic vasoconstrictor neurons in humans corresponding to mechanisms observed in animals, and 3) the described functional relation between bladder distension and sympathetic vasoconstrictor activity probably plays a role in clinical conditions such as autonomic dysreflexia in humans with cervical spinal cord lesions and nocturnal micturition syncope.

Hypogastric nerve activity to the feline bladder during slow filling

Hypogastric efferent nerve activity was measured in cats anaesthetised with a continuous pentobarbitone infusion while the bladder was filled at a physiological rate. Pelvic efferent nerve recording was used to determine the end of the continence process. The point in the continence process at which non-micturating contractions commenced was usually the point at which sympathetic nerve activity began to increase. By the time the continence process was half over, sympathetic nerve activity had increased from the resting level by 21%. There is disagreement about the role of the sympathetic innervation in the process of urine storage. In the present study, there appears to be significant sympathetic drive to the bladder for much of the continence process.

Multi- and single-fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats

1. In cats anaesthetized with alpha-chloralose and artificially respired, stimulation of intestinal receptors with bradykinin caused greater reflex excitation of mesenteric than of renal efferent multifibre nerve activity and significant pressor responses. 2. Activity of all nerve bundles used in this study was inhibited by stimulation of pressoreceptors. Increases in systemic arterial pressure caused inhibition of activity of renal nerves which was significantly greater than that of mesenteric nerves. 3. Spinal transection caused significant decreases in tonic renal nerve activity without altering the ongoing discharge rate of mesenteric nerves. Stimulation of intestinal receptors in spinal cats still caused significant increases is discharge of mesenteric and renal nerves, indicating that this reflex contains a spinal component. 4. Recordings of activity of individual fibres within mesenteric (21) and renal (23) nerves provided information regarding the basis for the multifibre responses to stimulation of intestinal receptors. The same proportion of fibres from both nerves was excited, but the increase in activity of mesenteric fibres was significantly greater than that of renal fibres. 5. Mesenteric fibres could be classified into two groups, based on their sensitivity to pressoreceptor influences. Fibres that exhibited pressoreceptor-independent discharge had the greatest responses to stimulation of intestinal receptors. 6. Following spinal transection the majority of mesenteric fibres continued to fire, whereas most renal fibres became quiescent. 7. The non-uniform pattern of neuronal excitation to chemical stimulation of intestinal receptors was manifest after spinal transection, demonstrating that exclusively spinal pathways can mediate this differential response pattern. 8. These results support the hypothesis that viscero-sympathetic reflexes may be organized to cause preferential excitation of neural activity directed to the organ from which the reflex originates.

Responses of sacral visceral afferents from the lower urinary tract, colon and anus to mechanical stimulation

The discharge characteristics of sacral visceral afferents supplying the urinary bladder, urethra, colon and anus to mechanical stimuli were analyzed in the anaesthetized cat. The stimuli used were passive distension (urinary bladder, colon), isovolumetric contraction (urinary bladder), movements of the urethral catheter and mechanical shearing stimuli (mucosal skin of the anal canal). (1) In total 245 afferent units which projected in the pelvic nerve were isolated from the sacral dorsal roots. From one of the following organs, urinary bladder, colon, urethra and anus 117 afferent units were activated. By these stimuli from the bladder, urethra and anus 122 afferent units could not be activated, and as far as tested also not from the colon; in 6 afferent units the classification was unclear. (2) Afferent units from the urinary bladder and the colon responded consistently to passive distension of the respective organ. The units from the urinary bladder showed graded responses at intraluminal pressures of about 10-70 mmHg and responded also to isovolumetric contractions of the organ. The thresholds of the units from the bladder to passive distension and contraction varied from about 5 to 20 mmHg intravesical pressure. (3) The afferent units from the urethra and the anus did not react or showed some weak phasic and irregular responses to distension and contraction applied to the urinary bladder or to distension of the colon. They were consistently excited by low threshold mechanical stimulation of the urethra and anus, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Capsaicin treatment attenuates the reflex excitation of sympathetic activity caused by chemical stimulation of intestinal afferent nerves

Sympathetic reflexes elicited by stimulation of visceral receptors have been well investigated, but the central neurotransmitters mediating these reflexes are largely unknown. Therefore, experiments were done to evaluate the role of substance P in the central transmission of a sympathoexcitatory reflex elicited by stimulation of intestinal receptors. Activity of mesenteric and renal nerves was recorded electrophysiologically in chloralose/urethane-anesthetized rats. Stimulation of intestinal receptors by serosal application of 0.5-1.0 microgram bradykinin increased mesenteric nerve activity by 100 +/- 21%, renal nerve discharge by 33 +/- 9%, and systemic arterial pressure by 10 mm Hg. Chronic capsaicin treatment (cumulative dose 950 mg/kg) caused a 52% depletion of substance P-like immunoreactivity from dorsal root ganglia and a significant attenuation of these reflexes. Mesenteric nerve activity increased by 48 +/- 6% in the capsaicin-treated rats. Bradykinin did not cause significant changes in renal nerve activity or systemic arterial pressure in these rats. The excitation of mesenteric nerve activity was significantly greater than the increase in renal nerve activity int he untreated and capsaicin-treated rats; capsaicin treatment affected responses of both nerves similarly. Capsaicin treatment did not have generalized effects on sympathetic reflexes, as mesenteric and renal nerve activities were decreased by baroreceptor activation similarly in the untreated and capsaicin-treated rats. These results suggest that the central transmission of the reflex response to intestinal receptor stimulation is mediated in part by substance P or other capsaicin-sensitive peptides.