Central representation of bladder and colon revealed by dual transsynaptic tracing in the rat: substrates for pelvic visceral coordination

Lifelong LUTS: Understanding the bladder's role and implications across transition phases, a comprehensive review

INTRODUCTION

Lower urinary tract symptoms (LUTSs) are a diverse array of urinary and pelvic dysfunctions that can emerge from childhood, extend through adulthood, and persist into older age. This narrative review aims to provide a comprehensive perspective on the continuum of LUTS and shed light on the underlying mechanisms and clinical implications that span across the lower urinary tract.

METHODS

A panel of five experts from Belgium, the Netherlands, India, Denmark, and the United States participated in an intensive research to explore and pinpoint existing insights into the lifelong concept of LUTS, particularly at the pelvic level. The experts reviewed the existing literature and held a webinar to discuss their findings.

RESULTS

Childhood LUTS can persist, resolve, or progress into bladder underactivity, dysfunctional voiding, or pain syndromes. The Lifelong character can be explained by pelvic organ cross-talk facilitated through complex neurological and nonneurological interactions. At the molecular level, the role of vasopressin receptors in the bladder's modulation and their potential relevance to therapeutic strategies for LUTS are explored. Frailty emerges as a parallel concept to lifelong LUTS, with a complex and synergistic relationship. Frailty, not solely an age-related condition, accentuates LUTS severity with insufficient evidence regarding the effectiveness and safety profile of the available therapeutic modalities.

CONCLUSION

Understanding lifelong LUTSs offers insights into genetic, anatomical, neurological, and molecular mechanisms. Further research could identify predictive biomarkers, elucidate the role of clinically translatable elements in pelvic cross-talk, and uncover molecular signatures for personalized management.

Activation of CRF1 receptors expressed in brainstem autonomic nuclei stimulates colonic enteric neurons and secreto-motor function in male rats

BACKGROUND

Hypothalamic corticotropin-releasing factor (CRF) receptor 1 (CRF1 ) plays a role in acute stress-related stimulation of colonic motor function. Less is known on CRF1 signaling in the brainstem.

METHODS

We investigate CRF1 expression in the brainstem and the colonic response to 4th ventricle (4V) injection of CRF and urocortin (Ucn) 2 (3 µg/rat) in chronically cannulated male rats.

KEY RESULTS

Transcripts of CRF1 wild-type 1a and splice variants 1c, 1e, 1f, 1o along with three novel variants 1a-2 (desK-110 in exon 5), 1p (-exon 7), and 1q (exon 5 extension) were identified in the pons and medulla. The area postrema, nucleus tractus solitarius, dorsal motor nucleus of the vagus, locus coeruleus, and Barrington's nucleus isolated by laser capture microdissection expressed 1a, 1a-2, and 1p but not 1q. Compared to 4V vehicle, 4V CRF induced fecal pellet output (FPO) and diarrhea that were blocked by the CRF antagonist, astressin-B. CRF2 agonist, Ucn2 had no effect on basal or CRF-induced FPO. CRF actions were correlated with the induction of c-Fos immunoreactivity in myenteric neurons of the proximal and distal colon (pC, dC) and submucosal neurons of dC. c-Fos immunoreactivity occurred in 39% and 37% of myenteric cholinergic and 7% and 58% of nitrergic neurons in the pC and dC, respectively.

CONCLUSIONS & INFERENCES

CRF1a and its splice variants are expressed in brainstem nuclei, and activation of CRF1 signaling at the level of the brainstem stimulates colonic secretory-motor function through activation of colonic enteric neurons.

Somatostatin Neurons in the Mouse Pontine Nucleus Activate GABAA Receptor Mediated Synaptic Currents in Locus Coeruleus Neurons

The pontine nuclei comprising the locus coeruleus (LC) and Barrington’s nucleus (BRN) amongst others form the neural circuitry(s) that coordinates arousal and voiding behaviors. However, little is known about the synaptic connectivity of neurons within or across these nuclei. These include corticotropin-releasing factor (CRF⁺) expressing neurons in the BRN that control bladder contraction and somatostatin expressing (SST⁺) neurons whose role in this region has not been discerned. To determine the synaptic connectivity of these neurons, we employed optogenetic stimulation with recordings from BRN and LC neurons in brain stem slices of channelrhodopsin-2 expressing SST or CRF neurons. Optogenetic stimulation of CRF⁺ BRN neurons of Crf^Cre;chr2-yfp mice had little effect on either CRF⁺ BRN neurons, CRF^– BRN neurons, or LC neurons. In contrast, in Sst^Cre;chr2-yfp mice light-activated inhibitory postsynaptic currents (IPSCs) were reliably observed in a majority of LC but not BRN neurons. The GABA_A receptor antagonist, bicuculline, completely abolished the light-induced IPSCs. To ascertain if these neurons were part of the neural circuitry that controls the bladder, the trans-synaptic tracer, pseudorabies virus (PRV) was injected into the bladder wall of Crf^Cre;tdTomato or Sst^Cre;tdTomato mice. At 68–72 h post-viral infection, PRV labeled neurons were present only in the BRN, being preponderant in CRF⁺ neurons with few SST⁺ BRN neurons labeled from the bladder. At 76 and 96 h post-virus injection, increased labeling was observed in both BRN and LC neurons. Our results suggest SST⁺ neurons rather than CRF⁺ neurons in BRN can regulate the activity of LC neurons.

Identification and characterization of rostral ventromedial medulla neurons synaptically connected to the urinary bladder afferents in female rats with or without neonatal cystitis

The neurons in the rostral ventromedial medulla (RVM) play a major role in pain modulation. We have previously shown that early-life noxious bladder stimuli in rats resulted in an overall spinal GABAergic disinhibition and a long-lasting bladder/colon sensitization when tested in adulthood. However, the neuromolecular alterations within RVM neurons in the pathophysiology of early life bladder inflammation have not been elucidated. In this study, we have identified and characterized RVM neurons that are synaptically linked to the bladder and colon and examined the effect of neonatal bladder inflammation on molecular expressions of these neurons. A transient bladder inflammation was induced by intravesicular instillation of protamine sulfate and zymosan during postnatal days 14 through 16 (P14-16) followed by pseudorabies virus PRV-152 and PRV-614 injections into the bladder and colon, respectively, on postnatal day P60. Tissues were examined 96 h postinoculation for serotonergic, GABAergic, and enkephalinergic expressions using in situ hybridization and/or immunohistochemistry techniques. The results revealed that > 50% of RVM neurons that are synaptically connected to the bladder (i.e., PRV-152+) were GABAergic, 40% enkephalinergic, and about 14% expressing serotonergic marker tryptophan hydroxylase 2 (TpH2). Neonatal cystitis resulted in a significant increase in converging neurons in RVM receiving dual synaptic inputs from the bladder and colon. In addition, neonatal cystitis significantly downregulated vesicular GABA transporter (VGAT) with a concomitant increase in TpH2 expression in bladder-linked RVM neurons, suggesting an alteration in supraspinal signaling. These alterations of synaptic connectivity and GABAergic/serotonergic expressions in RVM neurons may contribute to bladder pain modulation and cross-organ visceral sensitivity.

Interrogating autonomic peripheral nervous system neurons with viruses - A literature review

How rich functionality emerges from the rather invariant structural architecture of the peripheral autonomic nervous system remains one of the major mysteries in neuroscience. The high incidence of patients with neural circuit-related autonomic nervous system diseases highlights the importance of fundamental research, among others with neurotracing methods, into autonomic neuron functionality. Due to the emergence of neurotropic virus-based tracing techniques in recent years the access to neuronal connectivity in the peripheral autonomic nervous system has greatly been improved. This review is devoted to the anatomical distribution of neural circuits in the periphery of the autonomous nervous system and to the interaction between the autonomic nervous system and vital peripheral organs or tissues. The experimental evidence available at present has greatly expanded our understanding of autonomic peripheral nervous system neurons.

Neuropeptides' Hypothalamic Regulation of Sleep Control in Children Affected by Functional Non-Retentive Fecal Incontinence

Functional non-retentive fecal incontinence (FNRFI) is a common problem in pediatric age. FNRFI is defined as unintended loss of stool in a 4-year-old or older child after organic causes have been excluded. FNRFI tends to affects up to 3% of children older than 4 years, with males being affected more frequently than females. Clinically, children affected by FNRFI have normal intestinal movements and stool consistency. Literature data show that children with fecal incontinence have increased levels of separation anxiety, specific phobias, general anxiety, attention-deficit/hyperactivity disorder (ADHD), and oppositional defiant disorder. In terms of possible relationship between incontinence and sleep, disorders of sleep organization have been observed in the pathogenesis of enuresis so generating the hypothesis that the orexinergic system may have a crucial role not only for the sleep organization per se but also for the sphincterial control in general. This study aimed to focus on specific neurophysiological aspects to investigate on the possible relationship between sleep organizational abnormalities and FNRFI. Specifically, we aimed to measure orexin serum levels in children with FNRFI and assess their polysomnographic sleep macrostructure patterns. Two study groups were considered: FNFRI (n = 45) and typically developed (TD) (n = 45) group. In both groups, sleep patterns and respiratory events were assessed by polysomnographic recordings (PSG) during a period of two nights at least, and plasma levels of Orexin-A were measured in each participant. The findings of this initial investigation seem to support a major role of Orexin-A in sleep organization alterations in children with FNFRI. Also, our data suggest that sleep habits evaluation should be considered as screening and complementary tool for the diagnosis of fecal incontinence in children.

Central pattern generators in the brainstem and spinal cord: an overview of basic principles, similarities and differences

Central pattern generators (CPGs) are generally defined as networks of neurons capable of enabling the production of central commands, specifically controlling stereotyped, rhythmic motor behaviors. Several CPGs localized in brainstem and spinal cord areas have been shown to underlie the expression of complex behaviors such as deglutition, mastication, respiration, defecation, micturition, ejaculation, and locomotion. Their pivotal roles have clearly been demonstrated although their organization and cellular properties remain incompletely characterized. In recent years, insightful findings about CPGs have been made mainly because (1) several complementary animal models were developed; (2) these models enabled a wide variety of techniques to be used and, hence, a plethora of characteristics to be discovered; and (3) organizations, functions, and cell properties across all models and species studied thus far were generally found to be well-preserved phylogenetically. This article aims at providing an overview for non-experts of the most important findings made on CPGs in in vivo animal models, in vitro preparations from invertebrate and vertebrate species as well as in primates. Data about CPG functions, adaptation, organization, and cellular properties will be summarized with a special attention paid to the network for locomotion given its advanced level of characterization compared with some of the other CPGs. Similarities and differences between these networks will also be highlighted.

The complex relationship between urinary and defecatory disorders in young and adolescent girls

PURPOSE OF REVIEW

Scientific advancements have led to enhanced clarity about the interrelationship between urinary tract pathology and functional bowel disturbances. The present article will review the current literature regarding the cause, pathophysiology, diagnosis, and treatment of lower urinary tract dysfunction and abnormal bowel habits in young and adolescent girls.

RECENT FINDINGS

Complex neurological, physiological mechanisms and functional behaviors exist that contribute to the development of coexisting urinary symptoms and defecatory disorders in young and adolescent girls. Bladder bowel dysfunction (BBD) in childhood and adolescence is carried into adulthood creating a lifetime health burden.

SUMMARY

Practitioners should be aware and actively screen for conditions mimicking BBD with time-efficient and effective history-taking and physical exams that reduce anxiety and fear. The present review provides guide to comprehensive treatment strategies for managing complex pelvic floor disorders including urinary incontinence, defecatory disorders, pelvic and perineal pain, and constipation. More research is needed to elucidate pathophysiology and optimal treatment strategies of the BBD.

Effect of distal esophageal irritation on the changes of cystometry parameters to esophagus and colon distentions in rats

The coexistence of different visceral pathologies in patients suffering from irritable bowel syndrome, interstitial cystitis, and other pathologies, necessitates the study of these pathologies under complicated conditions. In the present study, cystometry recordings were used to investigate the effect of distal esophageal chemical irritation on the urinary bladder interaction with distal colon distention, distal esophageal distention, and electrical stimulation of abdominal branches of vagus nerve. Distal esophageal chemical irritation significantly decreased the intercontraction time via decreasing the voiding time. Also, distal esophageal chemical irritation significantly decreased the pressure amplitude by decreasing the maximum pressure. Following distal esophageal chemical irritation, distal esophageal distention was able to significantly decrease the intercontraction time by decreasing the storage time. However, 3 mL distal colon distention significantly increased the intercontraction time by increasing the storage time. On the other hand, following distal esophageal chemical irritation, electrical stimulation of abdominal branches of vagus nerve did not have any significant effect on intercontraction time. However, electrical stimulation of abdominal branches of vagus nerve significantly increased the pressure amplitude by increasing the maximum pressure. The results of this study demonstrate that urinary bladder function and interaction of bladder with other viscera can be affected by chemical irritation of distal esophagus.

FUNCTIONAL CONSTIPATION AND OVERACTIVE BLADDER IN WOMEN: A POPULATION-BASED STUDY

ABSTRACT BACKGROUND: An association between urinary disorders and functional constipation has been registered in children and adults, with functional constipation being a common complaint in individuals with overactive bladder. OBJECTIVE: To evaluate the prevalence of functional constipation, overactive bladder and its dry/wet subtypes in women and to determine which bowel symptoms predict overactive bladder. METHODS: A cross-sectional study of women randomly approached in public spaces. Exclusion criteria: neurological/anatomical abnormalities of the bowel or urinary tract. Constipation was defined as ≥2 positive symptoms of those listed in the Rome criteria. Urinary abnormalities (frequent urination, urgency, incontinence, nocturia) were defined by a score ≥2 in the respective item of the International Consultation on Incontinence Questionnaire - Overactive Bladder. Dry overactive bladder was defined as urgency without incontinence, while wet overactive bladder included incontinence. RESULTS: A total of 516 women with a mean age of 35.8±6 years were interviewed. Rates of functional constipation, overactive bladder, dry overactive bladder and wet overactive bladder were 34.1%, 15.3%, 8.9% and 6.4%, respectively. Functional constipation was associated with overactive bladder and dry overactive bladder, with functional constipation predicting dry overactive bladder (OR=2.47). Quality of life was poorer in constipated women compared to non-constipated and even worse in constipated women with wet overactive bladder (median 22.5; 95%CI: 17.25-35.25). Manual maneuvers were significantly associated with both overactive bladder subtypes. Independent predictive factors for overactive bladder were manual maneuvers (OR=2.21) and <3 defecations/week (OR=2.18), with the latter being the only predictive factor for dry overactive bladder (OR=3.0). CONCLUSION: Functional constipation is associated with overactive bladder and its dry subtype, particularly in the younger population. In addition, this association is responsible for lower quality of life scores, especially when urinary incontinence is present. The presence of manual maneuvers and less than three defecations per week should direct us to look for overactive bladder.

Transsynaptic tracing to dissect supraspinal serotonergic input regulating the bladder reflex in rats

AIMS

This study was designed to determine specific cell groups of the raphe nuclei (RN) that give rise to supraspinal serotonergic projections regulating the bladder reflex.

METHODS

Anesthetized rats underwent surgery to open the abdomen and expose the bladder. A total of 6 µL transsynaptic neuronal tracer pseudorabies virus (PRV-152), encoding for green fluorescent protein (GFP), was injected into the bladder detrusor. After 72 or 96 h, animals were perfused and the brain was dissected for processing transverse and sagittal sections. Subsequently, fluorescent immunohistochemistry for GFP and Serotonin (5-hydroxytryptamine [5-HT]) was performed in the brain sections. Under the microscope, each RN subset was characterized individually from caudal to rostral according to the atlas. GFP⁺ or GFP/5-HT double labeled neurons in each subset were quantified for statistical analysis.

RESULTS

At 72-h post-infection, very few GFP⁺ or GFP/5-HT double-labeled neurons appeared in the brainstem and beyond. In contrast, many labeled neurons were found at these levels after 96 h. Quantitative analysis showed that the majority of infected 5-HT⁺ neurons were located in the pallidus, obscurus, and magnus nuclei. Conversely, very few infected neurons were found in other raphe subsets, that is the pontis, median, dorsal, or linear nuclei. Overall, the raphe magnus had the highest number of GFP-labeled and GFP/5-HT double-labeled cells.

CONCLUSIONS

The caudal subsets of RN, especially the raphe magnus, are the main sources of serotonergic input to the lower spinal cord controlling bladder activity.

The Influence of Early Life Experience on Visceral Pain

Pain is the most reported and troublesome symptom of nearly all functional disorders affecting the genitourinary and gastrointestinal organs. Patients with irritable bowel syndrome (IBS), interstitial cystitis/painful bladder syndrome (IC/PBS), vulvodynia, and/or chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS; collectively termed chronic pelvic pain syndromes) report pain severe enough to impact quality of life and often suffer from symptoms of or are diagnosed with more than one of these syndromes. This increased comorbidity between chronic pelvic pain syndromes, and with pain disorders of disparate body regions, as well as with mood disorders, can be influenced by disruptions in the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the response to stress and influences the perception of pain. Experiencing trauma, neglect, or abuse in early life can permanently affect the functioning of the HPA axis. As such, a significant proportion of patients suffering from comorbid chronic pelvic pain syndromes report a history of early life stress or trauma. Here we will report on how these early life experiences influence chronic pelvic pain in patients. We will also discuss various rodent models that have been developed to study this phenomenon to understand the mechanisms underlying HPA axis dysfunction, as well as potential underlying mechanisms connecting these syndromes to one another.

Management of Neurogenic Bladder

This article provides a comprehensive summary of the clinical approach, investigative modalities and management of a child with neurogenic bladder disease due to myelodysplasia. It is aimed at pediatric physicians and surgeons working in developing nations. The methodologies suggested are simple and can be practised even in resource poor regions. The goal of management is avoidance of Chronic kidney disease and for this, meticulous bladder management is the key.

Genitourinary and gastrointestinal co-morbidities in children: The role of neural circuits in regulation of visceral function

OBJECTIVE

Pediatric lower urinary tract dysfunction (LUTD) is a common problem in childhood. Lower urinary tract symptoms in children include overactive bladder, voiding postponement, stress incontinence, giggle incontinence, and dysfunctional voiding. Gastrointestinal co-morbidities, including constipation or fecal incontinence, are commonly associated with lower urinary tract (LUT) symptoms in children, often reaching 22-34%. This review summarized the potential mechanisms underlying functional lower urinary and gastrointestinal co-morbidities in children. It also covered the current understanding of clinical pathophysiology in the pediatric population, anatomy and embryological development of the pelvic organs, role of developing neural circuits in regulation of functional co-morbidities, and relevant translational animal models.

MATERIALS AND METHODS

This was a non-systematic review of the published literature, which summarized the available clinical and translational studies on functional urologic and gastrointestinal co-morbidities in children, as well as neural mechanisms underlying pelvic organ 'cross-talk' and 'cross-sensitization'.

RESULTS

Co-morbidity of pediatric lower urinary and gastrointestinal dysfunctions could be explained by multiple factors, including a shared developmental origin, close anatomical proximity, and pelvic organ 'cross-talk'. Daily physiological activity and viscero-visceral reflexes between the lower gastrointestinal and urinary tracts are controlled by both autonomic and central nervous systems, suggesting the dominant modulatory role of the neural pathways. Recent studies have provided evidence that altered sensation in the bladder and dysfunctional voiding can be triggered by pathological changes in neighboring pelvic organs due to a phenomenon known as pelvic organ 'cross-sensitization'. Cross-sensitization between pelvic organs is thought to be mainly coordinated by convergent neurons that receive dual afferent inputs from discrete pelvic organs. Investigation of functional changes in nerve fibers and neurons sets certain limits in conducting appropriate research in humans, making the use of animal models necessary to uncover the underlying mechanisms and for the development of novel therapeutic approaches for long-term symptomatic treatment of LUTD in the pediatric population.

CONCLUSION

Pediatric LUTD is often complicated by gastrointestinal co-morbidities; however, the mechanisms linking bladder and bowel dysfunctions are not well understood. Clinical studies have suggested that therapeutic modulation of one system may improve the other system's function. To better manage children with LUTD, the interplay between the two systems, and how co-morbid GI and voiding dysfunctions can be more specifically targeted in pediatric clinics need to be understood.

Sympathetic preganglionic neurons: properties and inputs

The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.

Voiding Dysfunction: What Can Radiologists Tell Patients and Pediatric Urologists?

OBJECTIVE

Imaging children with dysfunctional voiding remains a challenge because 98% of these children have normal anatomy. Identifying the 1-2% of children who do have an anatomic basis for incontinence is important; this article focuses on how pediatric urologists use imaging for the evaluation of patients with this condition.

CONCLUSION

Imaging a patient with dysfunctional voiding can provide findings that will allow an accurate diagnosis and lead to optimal management. The key for the pediatric urologist is using imaging studies judiciously because the diagnostic yield is low. If every patient with dysfunctional voiding who presents to the clinic undergoes imaging, there will be little gain. Understanding in which patients to try imaging sooner versus trying medical and behavioral management first is a function of experience.

Anatomy and physiology of the lower urinary tract

Functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. Neural control of micturition is organized as a hierarchic system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brainstem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brainstem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily during the early postnatal period, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults cause re-emergence of involuntary micturition, leading to urinary incontinence. The mechanisms underlying these pathologic changes are discussed.

Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions

Although the gastrointestinal (GI) tract possesses intrinsic neural plexuses that allow a significant degree of autonomy over GI functions, the central nervous system (CNS) provides extrinsic neural inputs that regulate, modulate, and control these functions. While the intestines are capable of functioning in the absence of extrinsic inputs, the stomach and esophagus are much more dependent upon extrinsic neural inputs, particularly from parasympathetic and sympathetic pathways. The sympathetic nervous system exerts a predominantly inhibitory effect upon GI muscle and provides a tonic inhibitory influence over mucosal secretion while, at the same time, regulates GI blood flow via neurally mediated vasoconstriction. The parasympathetic nervous system, in contrast, exerts both excitatory and inhibitory control over gastric and intestinal tone and motility. Although GI functions are controlled by the autonomic nervous system and occur, by and large, independently of conscious perception, it is clear that the higher CNS centers influence homeostatic control as well as cognitive and behavioral functions. This review will describe the basic neural circuitry of extrinsic inputs to the GI tract as well as the major CNS nuclei that innervate and modulate the activity of these pathways. The role of CNS-centered reflexes in the regulation of GI functions will be discussed as will modulation of these reflexes under both physiological and pathophysiological conditions. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide these answers.

Identification of autonomic neuronal chains innervating gingiva and lip

The major goals of this present study were 1) to further clarify which parasympathetic ganglion sends postganglionic fibers to the lower gingiva and lip that may be involved in the inflammatory processes besides the local factors; 2) to separately examine the central pathways regulating sympathetic and parasympathetic innervation; and 3) to examine the distribution of central premotor neurons on both sides. A retrogradely transported green fluorescent protein conjugated pseudorabies virus was injected into the lower gingiva and lip of intact and sympathectomized adult female rats. Some animals received virus in the adrenal medulla which receive only preganglionic sympathetic fibers to separately clarify the sympathetic nature of premotor neurons. After 72-120h of survival and perfusion, the corresponding thoracic part of the spinal cord, brainstem, hypothalamus, cervical, otic, submandibular and trigeminal ganglia were harvested. Frozen sections were investigated under a confocal microscope. Green fluorescence indicated the presence of the virus. The postganglionic sympathetic neurons related to both organs are located in the three cervical ganglia, the preganglionic neurons in the lateral horn of the spinal cord on ipsilateral side; premotor neurons were found in the ventrolateral medulla, locus ceruleus, gigantocellular and paraventricular nucleus and perifornical region in nearly the same number on both sides. The parasympathetic postganglionic neurons related to the gingiva are present in the otic and related to the lip are present in the otic and submandibular ganglia and the preganglionic neurons are in the salivatory nuclei. Third order neurons were found in the gigantocellular reticular and hypothalamic paraventricular nuclei and perifornical area.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Neurobiological mechanisms of pelvic pain

Pelvic pain is a common condition which significantly deteriorates health-related quality of life. The most commonly identified causes of pain in the pelvic region are gynaecologic, urologic, gastrointestinal, neurological, and musculoskeletal. However, in up to 33% of patients the source of this symptom is not identified, frustrating both patients and health-care professionals. Pelvic pain may involve both the somatic and visceral systems, making the differential diagnosing challenging. This paper aimed to review the mechanisms involved in pelvic pain perception by analyzing the neural plasticity and molecules which are involved in these complex circuits.

Cross-sensitization mechanisms between colon and bladder via transient receptor potential A1 stimulation in rats

INTRODUCTION AND HYPOTHESIS

The aim of this study was to analyze the mechanism underlying cross-sensitization between the colon and the bladder via activation of transient receptor potential A1 (TRPA1) channels.

METHODS

Using female Sprague-Dawley rats, polyethylene catheters were inserted into the colon between two ligations at the levels of 40 and 60 mm rostral to the anus and into the bladder. (1) We examined changes in colon and bladder activity after the application of allyl isothiocyanate (AI, 50 mM, 300 μl), a TRPA1 activator, into the colon or the bladder in an awake condition. Inhibitory effects of the pretreatment with HC-030031 (HC, 3 mg/kg), a TRPA1 inhibitor, on colon-to-bladder cross-sensitization induced by AI instilled in the colon were also investigated. (2) We examined Evans blue (EB) dye extravasation after TRPA1 stimulation in the colon or the bladder to evaluate vascular permeability due to tissue inflammation.

RESULTS

(1) Intercontraction intervals during continuous saline infusion into the bladder (0.04 ml/min) were significantly decreased after the intracolonic AI application, which significantly increased mean intracolonic pressure, indicative of colon-to-bladder cross-sensitization. The AI-induced colon-to-bladder cross-sensitization was completely prevented by the pretreatment with intravenous application of HC. On the other hand, mean intracolonic pressure was significantly decreased after the intravesical AI application, which significantly increased mean intravesical pressure. (2) EB dye extravasation was significantly increased in the AI-treated inflamed organs and also in the bladder following intracolonic AI treatment.

CONCLUSIONS

Colon-to-bladder cross-sensitization is mediated via TRPA1 stimulation in the colon, although TRPA1 expressed in the bladder does not seem to participate in bladder-to-colon cross-sensitization.

Functional role of Barrington's nucleus in the micturition reflex: relevance in the surgical treatment of Parkinson's disease

The pontine micturition center or Barrington's nucleus (BN) - besides regulating micturition - co-regulates the activity of other pelvic viscera such as the colon and genitals. At present, this issue is gaining particular importance due to: (i) recent findings of α-synuclein in BN, (ii) known urinary dysfunction in parkinsonian patients (part of the so-called non-motor symptoms), other patients with dementia and as in very old individuals; and (iii) its proximity to the pedunculopontine nucleus, a surgical target in deep brain stimulation for Parkinson's disease (PD). The structural and functional organization of the micturition reflex comprises a coordinating action of somatic motor activity with both divisions of the autonomic nervous system, modulated by trunk encephalic and cortical centers that involve the BN as locus coeruleus and periaqueductal gray matter, among other trunk encephalic structures. The involvement of dopaminergic activity (physiologic inhibition of the micturition reflex mediated by dopaminergic D1 activity) that diminishes in Parkinsonism and leads to overactivity of the micturition reflex is also well known. In this review, the integrating role of the BN in the context of vesical and gastrointestinal behavior is revisited, and the principal morpho-functional findings that associate dysfunction with the urinary disorders that appear during the pre-motor stages of PD are summarized.

The periaqueductal gray controls brainstem emotional motor systems including respiration

Respiration is a motor system essential for the survival of the individual and of the species. Because of its vital significance, studies on respiration often assume that breathing takes place independent of other motor systems. However, motor systems generating vocalization, coughing, sneezing, vomiting, as well as parturition, ejaculation, and defecation encompass abdominal pressure control, which involves changes in the respiratory pattern. The mesencephalic periaqueductal gray (PAG) controls all these motor systems. It determines the level setting of the whole body by means of its very strong projections to the ventromedial medullary tegmentum, but it also controls the cell groups that generate vocalization, coughing, sneezing, vomiting, as well as respiration. For this control, the PAG maintains very strong connections with the nucleus retroambiguus, which enables it to control abdominal and intrathoracic pressure. In this same context, the PAG also runs the pelvic organs, bladder, uterus, prostate, seminal vesicles, and the distal colon and rectum via its projections to the pelvic organ stimulating center and the pelvic floor stimulating center. These cell groups, via long descending projections, have direct control of the parasympathetic motoneurons in the sacral cord as well as of the somatic motoneurons in the nucleus of Onuf, innervating the pelvic floor. Respiration, therefore, is not a motor system that functions by itself, but is strongly regulated by the same systems that also control the other motor output systems.

A corticotropin-releasing factor receptor antagonist improves urodynamic dysfunction produced by social stress or partial bladder outlet obstruction in male rats

Barrington's nucleus, in the pons, regulates micturition through spinal projections to preganglionic parasympathetic neurons. The stress neuropeptide CRF is prominent in these projections and has an inhibitory influence. Social stress in rats causes urinary retention and abnormal urodynamics resembling those produced by partial bladder outlet obstruction (pBOO), and this is associated with CRF upregulation in Barrington's nucleus. Here, we examined the role of CRF in social stress- and pBOO-induced urodynamic dysfunction by assessing the ability of a CRF₁ receptor antagonist to alter these effects. Male rats exposed to repeated resident-intruder stress were administered vehicle or a CRF₁ antagonist (NBI-30775) daily prior to the stress. Urodynamic function was recorded in the unanesthetized state 72 h after the final stress. NBI-30775 prevented the increased intermicturition interval, micturition volume, and bladder capacity produced by social stress, but not the increase in CRF expression in Barrington's nucleus neurons. The urinary dysfunction was also partly prevented by shRNA targeting of CRF in Barrington's nucleus, suggesting that stress-induced urinary dysfunction results, in part, from CRF upregulation in Barrington's nucleus and enhanced postsynaptic effects in the spinal cord. Finally, NBI-30775 improved urodynamic function of rats that had pBOO of 2-wk duration when administered daily during the second week but did not block the increase in CRF expression in Barrington's nucleus neurons. These findings implicate a role for Barrington's nucleus CRF in stress- and pBOO-induced urodynamic changes and suggest that CRF₁ antagonists may be useful therapeutic agents for the treatment of urinary dysfunction.

Anatomical and functional characterization of a duodeno-pancreatic neural reflex that can induce acute pancreatitis

Neural cross talk between visceral organs may play a role in mediating inflammation and pain remote from the site of the insult. We hypothesized such a cross talk exists between the duodenum and pancreas, and further it induces pancreatitis in response to intraduodenal toxins. A dichotomous spinal innervation serving both the duodenum and pancreas was examined, and splanchnic nerve responses to mechanical stimulation of these organs were detected. This pathway was then excited on the duodenal side by exposure to ethanol followed by luminal mustard oil to activate transient receptor potential subfamily A, member 1 (TRPA1). Ninety minutes later, pancreatic inflammation was examined. Ablation of duodenal afferents by resiniferatoxin (RTX) or blocking TRPA1 by Chembridge (CHEM)-5861528 was used to further investigate the duodeno-pancreatic neural reflex via TRPA1. ~40% of dorsal root ganglia (DRG) from the spinal cord originated from both duodenum and pancreas via dichotomous peripheral branches; ~50% splanchnic nerve single units responded to mechanical stimulation of both organs. Ethanol sensitized TRPA1 currents in cultured DRG neurons. Pancreatic edema and myeloperoxidase activity significantly increased after intraduodenal ethanol followed by mustard oil (but not capsaicin) but significantly decreased after ablation of duodenal afferents by using RTX or blocking TRPA1 by CHEM-5861528. We found the existence of a neural cross talk between the duodenum and pancreas that can promote acute pancreatitis in response to intraduodenal chemicals. It also proves a previously unexamined mechanism by which alcohol can induce pancreatitis, which is novel both in terms of the site (duodenum), process (neurogenic), and receptor (TRPA1).

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.

Selective plasticity of primary afferent innervation to the dorsal horn and autonomic nuclei following lumbosacral ventral root avulsion and reimplantation in long term studies

Previous studies involving injuries to the nerves of the cauda equina and the conus medullaris have shown that lumbosacral ventral root avulsion in rat models results in denervation and dysfunction of the lower urinary tract, retrograde and progressive cell death of the axotomized motor and parasympathetic neurons, as well as the emergence of neuropathic pain. Root reimplantation has also been shown to ameliorate several of these responses, but experiments thus far have been limited to studying the effects of lesion and reimplantation local to the lumbosacral region. Here, we have expanded the region of investigation after lumbosacral ventral root avulsion and reimplantation to include the thoracolumbar sympathetic region of the spinal cord. Using a retrograde tracer injected into the major pelvic ganglion, we were able to define the levels of the spinal cord that contain sympathetic preganglionic neurons innervating the lower urinary tract. We have conducted studies on the effects of the lumbosacral ventral root avulsion and reimplantation models on the afferent innervation of the dorsal horn and autonomic nuclei at both thoracolumbar and lumbosacral levels through immunohistochemistry for the markers calcitonin gene-related peptide (CGRP) and vesicular glutamate transporter 1 (VGLUT1). Surprisingly, our experiments reveal a selective and significant decrease of CGRP-positive innervation in the dorsal horn at thoracolumbar levels that is partially restored with root reimplantation. However, no similar changes were detected at the lumbosacral levels despite the injury and repair targeting efferent neurons, and being performed at the lumbosacral levels. Despite the changes evident in the thoracolumbar dorsal horn, we find no changes in afferent innervation of the autonomic nuclei at either sympathetic or parasympathetic segmental levels by CGRP or VGLUT1. We conclude that even remote, efferent root injuries and repair procedures can have an effect on remote and non-lesioned sensory systems sharing common peripheral ganglia.

Effect of unilateral subthalamic deep brain stimulation on rat digestive motor activity

A significant proportion of patients with Parkinson's disease suffers from digestive symptoms. Bilateral deep brain stimulation of the subthalamic nucleus has become a reliable therapeutic option for parkinsonian patients, but its effects on digestive motility remain poorly investigated. The aim of our study was to assess whether subthalamic stimulation could induce changes in gastric, colonic, and rectal motility and modulate brain centers involved in gut motility.

METHODS

In anesthetized rats, unilateral subthalamic nucleus stereotactic implantation was performed while intra-gastric, -colonic, and -rectal pressures were recorded during the ON and OFF periods of the stimulation. c-Fos protein expression was quantified by immunostaining in the nucleus of the solitary tract, the dorsal motor nucleus of the vagus nerve, the locus coeruleus, and the Barrington's nucleus.

RESULTS

Compared to baseline, sham stimulation did not change phasic gastric, colonic or rectal motor activity. Unilateral subthalamic stimulation increased colonic phasic motility (P<0.05) compared to baseline and the OFF period with no change in gastric and rectal motility. Pre-treatment with atropine, or specific D1 and D2 receptors antagonists prevented the rise in colonic motor activity. An increase in c-Fos protein-positive cells within all the studied nuclei was observed in the stimulated group compared to the sham group.

CONCLUSIONS

Unilateral subthalamic stimulation impacts on gut motility in anesthetized rats with a significant increase in colonic motility probably via the modulation of several brain centers. These findings warrant further confirmation in parkinsonian rat models before being transposed to clinical conditions.

Time-dependent changes in bladder function and plantar sensitivity in a rat model of fibromyalgia syndrome induced by hydrochloric acid injection into the gluteus

OBJECTIVE

To examine the correlation between muscular pain and bladder hypersensitivity in order to clarify the pathogenesis of comorbidity of bladder pain syndrome/interstitial cystitis with other chronic pain conditions such as fibromyalgia syndrome (FMS).

MATERIALS AND METHODS

Under isoflurane anaesthesia, 0.2 mL of hydrochloric acid (HCl) solution (pH 4.0) was injected into the bilateral gluteus muscles of female Sprague-Dawley rats to produce an FMS model, as the gluteus is one of the specific tender points in patients with FMS. Control rats received saline injection (0.2 mL). The mechanical sensitivity of the plantar was evaluated using the mean number of bilateral hindlimb withdrawals in response to tactile stimulation with a 2.0-g von Frey filament at 1, 2 and 3 weeks after the HCl injection. In a separate rat group, cystometry was performed with the rats awake during saline infusion (0.06 mL/min) into the bladder before and after 1% lidocaine injection (0.2 mL) into the bilateral gluteus 1, 2 and 3 weeks after the HCl injection.

RESULTS

The mean number of hindlimb withdrawals was significantly higher in FMS rats than in controls at 1 and 2 weeks. Using cystometry, we found that the intercontraction interval (ICI) and voided volume (VV) were significantly lower in FMS rats than in controls at 1 and 2 weeks. In addition, the voiding threshold pressure, ICI and VV were significantly higher after lidocaine injection in FMS rats, but not in controls, at 1 and 2 weeks.

CONCLUSIONS

HCl injection (pH 4.0) into the gluteus can induce plantar hypersensitivity and urinary frequency for up to 2 weeks after the injection, suggesting that somatic (gluteus)-to-visceral (bladder) cross-sensitization might underlie bladder hypersensitivity in patients with FMS. Moreover, intervention at specific tender points outside the bladder could be effective in treating urinary frequency because lidocaine injection into the gluteus normalized bladder function in FMS rats for up to 2 weeks.

The bladder-brain connection: putative role of corticotropin-releasing factor

The coordination of pelvic visceral activity with appropriate elimination behaviors is a complex task that requires reciprocal communication between the brain and pelvic organs. Barrington's nucleus, located in the pons, is central to a circuit involved in this function. Barrington's nucleus neurons project to both pelvic visceral motorneurons and cerebral norepinephrine neurons that modulate behavior. This circuit coordinates the descending limb of the micturition reflex with a central limb that initiates arousal and shifts the focus of attention to facilitate elimination behavior. The same circuitry that links the bladder and brain enables pathological processes in one target of the circuit to be expressed in the other. Urological disorders can, therefore, have cognitive and behavioral consequences by affecting components of this circuit; and in the opposing direction, psychosocial stressors can produce voiding dysfunctions and bladder pathology. The stress-related neuropeptide, corticotropin-releasing factor, which is prominent in Barrington's nucleus neurons, is a potential mediator of these effects.

Neural control of the lower urinary and gastrointestinal tracts: supraspinal CNS mechanisms

Normal urinary function is contingent upon a complex hierarchy of CNS regulation. Lower urinary tract afferents synapse in the dorsal horn of the spinal cord and ascend to the midbrain periaqueductal gray (PAG), with a separate nociception path to the thalamus. A spino-thalamo-cortical sensory pathway is present in some primates, including humans. In the brainstem, the pontine micturition center (PMC) is a convergence point of multiple influences, representing a co-ordinating center for voiding. Many PMC neurones have characteristics necessary to categorize the center as a pre-motor micturition nucleus. In the lateral pontine brainstem, a separate region has some characteristics to suggest a "continence center." Cerebral control determines that voiding is permitted if necessary, socially acceptable and in a safe setting. The frontal cortex is crucial for decision making in an emotional and social context. The anterior cingulate gyrus and insula co-ordinate processes of autonomic arousal and visceral sensation. The influence of these centers on the PMC is primarily mediated via the PAG, which also integrates bladder sensory information, thereby moderating voiding and storage of urine, and the transition between the two phases. The parabrachial nucleus in the pons is also important in behavioral motivation of waste evacuation. Lower urinary tract afferents can be modulated at multiple levels by corticolimbic centers, determining the interoception of physiological condition and the consequent emotional motor responses. Alterations in cognitive modulation, descending modulation, and hypervigilance are important in functional (symptom-based) clinical disorders.

Visceral organ cross-sensitization - an integrated perspective

Viscero-somatic referral and sensitization has been well documented clinically and widely investigated, whereas viscero-visceral referral and sensitization (termed cross-organ sensitization) has only recently received attention as important to visceral disease states. Because second order neurons in the CNS have been extensively shown to receive convergent input from different visceral organs, it has been assumed that cross-organ sensitization arises by the same convergence-projection mechanism as advanced for viscero-somatic referral and sensitization. However, increasing evidence also suggests participation of peripheral mechanisms to explain referral and sensitization. We briefly summarize behavioral, morphological and physiological support of and focus on potential mechanisms underlying cross-organ sensitization.

Neural control of the lower urinary tract: peripheral and spinal mechanisms

This review deals with individual components regulating the neural control of the urinary bladder. This article will focus on factors and processes involved in the two modes of operation of the bladder: storage and elimination. Topics included in this review include: (1) The urothelium and its roles in sensor and transducer functions including interactions with other cell types within the bladder wall ("sensory web"), (2) The location and properties of bladder afferents including factors involved in regulating afferent sensitization, (3) The neural control of the pelvic floor muscle and pharmacology of urethral and anal sphincters (focusing on monoamine pathways), (4) Efferent pathways to the urinary bladder, and (5) Abnormalities in bladder function including mechanisms underlying comorbid disorders associated with bladder pain syndrome and incontinence.

Cystitis increases colorectal afferent sensitivity in the mouse

Studies in humans and rodents suggest that colon inflammation promotes urinary bladder hypersensitivity and, conversely, that cystitis contributes to colon hypersensitivity, events referred to as cross-organ sensitization. To investigate a potential peripheral mechanism, we examined whether cystitis alters the sensitivity of pelvic nerve colorectal afferents. Male C57BL/6 mice were treated with cyclophosphamide (CYP) or saline, and the mechanosensitive properties of single afferent fibers innervating the colorectum were studied with an in vitro preparation. In addition, mechanosensitive receptive endings were exposed to an inflammatory soup (IS) to study sensitization. Urinary bladder mechanosensitive afferents were also tested. We found that baseline responses of stretch-sensitive colorectal afferents did not differ between treatment groups. Whereas IS excited a proportion of colorectal afferents CYP treatment did not alter the magnitude of this response. However, the number of stretch-sensitive fibers excited by IS was increased relative to saline-treated mice. Responses to IS were not altered by CYP treatment, but the proportion of IS-responsive fibers was increased relative to saline-treated mice. In bladder, IS application increased responses of muscular afferents to stretch, although no differences were detected between saline- and CYP-treated mice. In contrast, their chemosensitivity to IS was decreased in the CYP-treated group. Histological examination revealed no changes in colorectum and modest edema and infiltration in the urinary bladder of CYP-treated mice. In conclusion, CYP treatment increased mechanical sensitivity of colorectal muscular afferents and increased the proportion of chemosensitive colorectal afferents. These data support a peripheral contribution to cross-organ sensitization of pelvic organs.

Recent findings on the organization of central nervous system structures involved in the innervation of endocrine glands and other organs; observations obtained by the transneuronal viral double-labeling technique

This review summarizes the data obtained with the aid of the recently introduced dual viral tracing technique, which uses isogenic recombinants of pseudorabies virus that express unique reporter gene. This approach made possible to explore simultaneously neural circuits of two organs. The results of these studies indicate: (1) there are neurons innervating exclusively a given organ; (2) left-sided predominance in the supraspinal innervation of the endocrine glands (adrenal, ovary) studied, so far; (3) viral co-infection of neurons, i.e., special neuronal populations coexist in different brain areas that are transsynaptically connected with both paired endocrine and non-endocrine organs, endocrine glands and non-endocrine organs, and organs of bodily systems other than the endocrine one. The number of common neurons seems to be related to the need of coordinating action of different systems. The data on co-infection of neurons suggest that the central nervous system has the capacity to coordinate different organ functions via common brain neurons providing supraspinal innervation of the organs.

Neural mechanisms of pelvic organ cross-sensitization

Clinical observations of viscerovisceral referred pain in patients with gastrointestinal and genitourinary disorders suggest an overlap of neurohumoral mechanisms underlying both bowel and urinary bladder dysfunctions. Close proximity of visceral organs within the abdominal cavity complicates identification of the exact source of chronic pelvic pain, where it originates, and how it relocates with time. Cross-sensitization among pelvic structures may contribute to chronic pelvic pain of unknown etiology and involves convergent neural pathways of noxious stimulus transmission from two or more organs. Convergence of sensory information from discrete pelvic structures occurs at different levels of nervous system hierarchy including dorsal root ganglia, the spinal cord and the brain. The cell bodies of sensory neurons projecting to the colon, urinary bladder and male/female reproductive organs express a wide range of membrane receptors and synthesize many neurotransmitters and regulatory peptides. These substances are released from nerve terminals following enhanced neuronal excitability and may lead to the occurrence of neurogenic inflammation in the pelvis. Multiple factors including inflammation, nerve injury, ischemia, peripheral hyperalgesia, metabolic disorders and other pathological conditions dramatically alter the function of directly affected pelvic structures as well as organs located next to a damaged domain. Defining precise mechanisms of viscerovisceral cross-sensitization would have implications for the development of effective pharmacological therapies for the treatment of functional disorders with chronic pelvic pain such as irritable bowel syndrome and painful bladder syndrome. The complexity of overlapping neural pathways and possible mechanisms underlying pelvic organ crosstalk are analyzed in this review at both systemic and cellular levels.

High ambient temperature increases 3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”)-induced Fos expression in a region-specific manner

3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy") is a popular drug that is often taken under hot conditions at dance clubs. High ambient temperature increases MDMA-induced hyperthermia and recent studies suggest that high temperatures may also enhance the rewarding and prosocial effects of MDMA in rats. The present study investigated whether ambient temperature influences MDMA-induced expression of Fos, a marker of neural activation. Male Wistar rats received either MDMA (10 mg/kg i.p.) or saline, and were placed in test chambers for 2 h at either 19 or 30 degrees C. MDMA caused significant hyperthermia at 30 degrees C and a modest hypothermia at 19 degrees C. The 30 degrees C ambient temperature had little effect on Fos expression in vehicle-treated rats. However MDMA-induced Fos expression was augmented in 15 of 30 brain regions at the high temperature. These regions included (1) sites associated with thermoregulation such as the median preoptic nucleus, dorsomedial hypothalamus and raphe pallidus, (2) the supraoptic nucleus, a region important for osmoregulation and a key mediator of oxytocin and vasopressin release, (3) the medial and central nuclei of the amygdala, important in the regulation of social and emotional behaviors, and (4) the shell of the nucleus accumbens and (anterior) ventral tegmental area, regions associated with the reinforcing effects of MDMA. MDMA-induced Fos expression was unaffected by ambient temperature at many other sites, and was diminished at high temperature at one site (the islands of Calleja), suggesting that the effect of temperature on MDMA-induced Fos expression was not a general pharmacokinetic effect. Overall, these results indicate that high temperatures accentuate key neural effects of MDMA and this may help explain the widespread use of the drug under hot conditions at dance parties as well as the more hazardous nature of MDMA taken under such conditions.

Cross-organ interactions between reproductive, gastrointestinal, and urinary tracts: modulation by estrous stage and involvement of the hypogastric nerve

Central nervous system neurons process information converging from the uterus, colon, and bladder, partly via the hypogastric nerve. This processing is influenced by the estrous cycle, suggesting the existence of an estrous-modifiable central nervous system substrate by which input from one pelvic organ can influence functioning of other pelvic organs. Here, we tested predictions from this hypothesis that acute inflammation of colon, uterine horn, or bladder would produce signs of inflammation in the other uninflamed organs (increase vascular permeability) and that cross-organ effects would vary with estrous and be eliminated by hypogastric neurectomy (HYPX). Under urethane anesthesia, the colon, uterine horn, or bladder of rats in proestrus or metestrus, with or without prior HYPX, was treated with mustard oil or saline. Two hours later, Evans Blue dye extravasation was measured to assess vascular permeability. Extravasation was increased in all inflamed organs, regardless of estrous stage. For rats in proestrus, but not metestrus, either colon or uterine horn inflammation significantly increased extravasation in the uninflamed bladder. Much smaller cross-organ effects were seen in colon and uterine horn. HYPX reduced extravasation in the inflamed colon and inflamed uterine horn, but not the inflamed bladder. HYPX eliminated the colon-to-bladder and uterine horn-to-bladder effects. These results demonstrate that inflaming one pelvic organ can produce estrous-modifiable signs of inflammation in other pelvic organs, particularly bladder, and suggest that the cross-organ effects involve the hypogastric nerve and are at least partly centrally mediated. Such effects could contribute to cooccurrence and cyclicity of distressing pelvic disorders in women.

Convergence of multiple pelvic organ inputs in the rat rostral medulla

Electrophysiological recordings were used to investigate the degree of pelvic/visceral convergent inputs onto single medullary reticular formation (MRF) neurons. A total of 94 MRF neurons responsive to bilateral electrical stimulation of the pelvic nerve (PN) in 12 urethane-anaesthetized male rats were tested for responses to mechanical stimulation of the urinary bladder, urethra, colon and penis, and electrical stimulation of the dorsal nerve of the penis (DNP) and abdominal branches of the vagus. Responses to distension of the bladder were found for 51% (n = 48) of the MRF neurons tested. Of these 48, 71% responded to urethral infusion, 81% responded to colon distension, 100% responded to penile stimulation (and DNP), and 85% responded to vagal stimulation, with 62% responding to stimulation of all four of these territories. This high degree of visceral convergence (i.e. 62%) in a subset of PN-responsive MRF neurons is significantly greater than for the subset of PN-responsive MRF neurons that did not respond to urinary bladder distension (i.e. out of the 46 remaining neurons, none responded to all four of the other pelvic/visceral stimuli combined). These results suggest that the neurons processing information from the urinary bladder at this level of the neural axis are likely to be important for mediating interactions between different visceral organs for the coordination of multiple pelvic/visceral functions.

Proximal colon distension induces Fos expression in the brain and inhibits gastric emptying through capsaicin-sensitive pathways in conscious rats

We assessed brain nuclei activated during noxious mechanical distension of the proximal colon in conscious rats, using Fos as a marker of neuronal activation, and functional reflex changes in gastric emptying associated to colon distension. The role of capsaicin-sensitive afferents in Fos and gastric responses to distension was also investigated. Compared with sham distension, isovolumetric phasic distension of the proximal colon (10 ml, 30 s on/off for 10 min) increased significantly Fos expression 1 h after distension in selective brain areas, most prominently, the paraventricular and supraoptic nuclei of the hypothalamus (13-fold and 80-fold, respectively), the locus coeruleus-Barrington's nucleus complex (2-fold), area postrema (7-fold) and the nucleus tractus solitarius (4-fold). Increased Fos expression was also observed in the cingulate cortex, posterior paraventricular nucleus of the thalamus, periaqueductal gray and ventrolateral medulla. Distension of the proximal colon significantly inhibited gastric emptying by 82% and 34%, as measured 30 and 60 min after the distension respectively, compared with control. Pretreatment with systemic capsaicin prevented both the brain increase in Fos expression and the inhibition of gastric emptying induced by the colon distension. These results show that visceral pain arising from the proximal colon activates a complex neuronal network that includes specific brain nuclei involved in the integration of autonomic, neuroendocrine and behavioral responses to pain and an inhibitory motor reflex in other gut areas (delayed gastric emptying). Capsaicin-sensitive afferent pathways are involved in mediating brain neuronal activation and functional changes associated with noxious visceral stimulation.

Impact of state of arousal and stress neuropeptides on urodynamic function in freely moving rats

Corticotropin-releasing factor (CRF) is a neurotransmitter in Barrington's nucleus neurons. These neurons can coregulate parasympathetic tone to the bladder (to modulate micturition) and brain noradrenergic activity (to affect arousal). To identify the role of CRF in the regulation of micturition, the effects of CRF agonists and antagonists on urodynamics in the unanesthetized rat were characterized. Rats were implanted with bladder and intrathecal or intraperitoneal catheters under isoflurane anesthesia. Cystometry was performed in the unanesthetized, unrestrained state at least 24 h later. In some cases, cortical electroencephalographic activity (EEG) was recorded simultaneously to assess arousal state. During cystometry, the state of arousal often shifted between waking and sleeping and urodynamic function changed depending on the state. Micturition threshold, bladder capacity, and micturition volume were all increased during sleep. The CRF1/CRF2 receptor agonists CRF and urocortin 2 increased bladder capacity and micturition volume in awake but not in sleeping rats. Conversely, the CRF1 receptor antagonists antalarmin and NBI-30775 increased urinary frequency and decreased bladder capacity in awake rats. The present results demonstrate a profound effect of the state of arousal on urodynamic function and suggest that simultaneous monitoring of EEG and cystometry may provide a useful model for studying nocturnal enuresis and other urinary disorders. In addition, the results provide evidence for an inhibitory influence of CRF in the spinal pathway on micturition. Targeting the CRF system in the spinal cord may provide a novel approach for treating urinary disorders.