Distribution of neurons in the major pelvic ganglion of the rat which supply the bladder, colon or penis

An adeno-associated viral labeling approach to visualize the meso- and microanatomy of mechanosensory afferents and autonomic innervation of the rat urinary bladder

The urinary bladder is supplied by a rich network of sensory and autonomic axons, commonly visualized by immunolabeling for neural markers. This approach demonstrates overall network patterning but is less suited to understanding the structure of individual motor and sensory terminals within these complex plexuses. There is a further limitation visualizing the lightly myelinated (A-delta) class of sensory axons that provides the primary mechanosensory drive for initiation of voiding. Whereas most unmyelinated sensory axons can be revealed by immunolabeling for specific neuropeptides, to date no unique neural marker has been identified to immunohistochemically label myelinated visceral afferents. We aimed to establish a non-surgical method to visualize and map myelinated afferents in the bladder in rats. We found that in rats, the adeno-associated virus (AAV), AAV-PHP.S, which shows a high tropism for the peripheral nervous system, primarily transduced myelinated dorsal root ganglion neurons, enabling us to identify the structure and regional distribution of myelinated (mechanosensory) axon endings within the muscle and lamina propria of the bladder. We further identified the projection of myelinated afferents within the pelvic nerve and lumbosacral spinal cord. A minority of noradrenergic and cholinergic neurons in pelvic ganglia were transduced, enabling visualization and regional mapping of both autonomic and sensory axon endings within the bladder. Our study identified a sparse labeling approach for investigating myelinated sensory and autonomic axon endings within the bladder and provides new insights into the nerve-bladder interface.

Mapping afferent and pelvic postganglionic neurons of the urethra from female rats: The L6 DRG is the major primary afferent supplier

AIMS

To map sensory and pelvic postganglionic neurons from three different regions of the female rat urethra.

METHODS

The neuronal tracer True Blue (TB) was injected into the pre-pelvic, pelvic, and clitoral regions of the urethra from female Wistar rats. Seven days after TB injection, TB+ cells from the dorsal root ganglia (DRGs) and the major pelvic ganglion (MPG) were examined. The number and morphometry of TB+ cells were determined.

RESULTS

TB+ cells were mainly distributed in lumbar 1 (L1), lumbar 2 (L2), lumbar 6 (L6), and sacral 1 (S1) DRGs, and in the MPG. The mean number of sensory neurons was 1200 ± 143. TB injection in pre-pelvic and pelvic urethra labeled neurons in L1, L2, L6, and S1 DRGs. TB injection in clitoral urethra labeled neurons in L6 and S1 DRGs. L6 DRG contained >50% of the total urethral TB+ neurons, and ~80% of the clitoral region. The mean value of the total number of MPG TB+ neurons was 1217 ± 72. DRG and MPG neurons projecting to the urethra presented a somatotopic distribution.

CONCLUSIONS

The results demonstrated that L6 DRG is the major supplier of afferent innervation to the urethra, and that the distal urethral region is exclusively innervated by lower lumbosacral DRGs. Considering that electrical stimulation of sensory pudendal nerve improves overactive bladder, and that most of the sensory neurons in the distal urethra are from L6 DRG, electrical stimulation of this ganglion may be an innovative and effective neuromodulation therapy for neurogenic urinary dysfunctions.

Impact of prostatic radiation therapy on bladder contractility and innervation

AIMS

To determine the effect of prostatic radiation therapy (RT) on bladder contractility and morphology, and axon, or neuron profiles within the detrusor and major pelvic ganglia (MPG) in male rats.

METHODS

Male Sprague-Dawley rats (8 weeks) received a single dose of prostatic RT (0 or 22 Gy). Bladders and MPG were collected 2- and 10-weeks post-RT. Detrusor contractile responses to carbachol and electrical field stimulation (EFS) were measured. Bladders were stained with Masson's trichrome, and antibodies for nonspecific neuronal marker, cholinergic nerve marker choline acetyltransferase (ChAT), and alpha-smooth muscle actin. MPG gene expression was assessed by quantitative polymerase chain reaction for ubiquitin carboxy-terminal hydrolase L1 (Uchl1) and Chat.

RESULTS

At 2 weeks post-RT, bladder smooth muscle, detrusor cholinergic axon profiles, and MPG Chat gene expression were increased (p < .05), while carbachol and EFS-mediated contractions were decreased (p < .05). In contrast, at 10 weeks post-RT, nerve-mediated contractions were increased compared with control (p < .05), while bladder smooth muscle, detrusor cholinergic axon profiles, MPG Chat expression, and carbachol contractions had normalized. At both 2- and 10-weeks post-RT, there was no change in detrusor nonspecific axon profiles and MPG Uchl1 expression.

CONCLUSION

In a rat model, RT of the prostate and MPG was associated with early changes in MPG Chat gene expression, and bladder cholinergic axon profiles and smooth muscle content which resolved over time. After RT recovery, bladder contractility decreased early and increased by 10 weeks. Long-term changes to the MPG and increased bladder cholinergic axons may contribute to RT-induced bladder dysfunction in prostate cancer survivors.

Functional segregation within the pelvic nerve of male rats: a meso- and microscopic analysis

The pelvic splanchnic nerves are essential for pelvic organ function and have been proposed as targets for neuromodulation. We have focused on the rodent homologue of these nerves, the pelvic nerves. Our goal was to define within the pelvic nerve the projections of organ-specific sensory axons labelled by microinjection of neural tracer (cholera toxin, subunit B) into the bladder, urethra or rectum. We also examined the location of peptidergic sensory axons within the pelvic nerves to determine whether they aggregated separately from sacral preganglionic and paravertebral sympathetic postganglionic axons travelling in the same nerve. To address these aims, microscopy was performed on the major pelvic ganglion (MPG) with attached pelvic nerves, microdissected from young adult male Sprague-Dawley rats (6-8 weeks old) and processed as whole mounts for fluorescence immunohistochemistry. The pelvic nerves were typically composed of five discrete fascicles. Each fascicle contained peptidergic sensory, cholinergic preganglionic and noradrenergic postganglionic axons. Sensory axons innervating the lower urinary tract (LUT) consistently projected in specific fascicles within the pelvic nerves, whereas sensory axons innervating the rectum projected in a complementary group of fascicles. These discrete aggregations of organ-specific sensory projections could be followed along the full length of the pelvic nerves. From the junction of the pelvic nerve with the MPG, sensory axons immunoreactive for calcitonin gene-related peptide (CGRP) showed several distinct patterns of projection: some projected directly to the cavernous nerve, others projected directly across the surface of the MPG to the accessory nerves and a third class entered the MPG, encircling specific cholinergic neurons projecting to the LUT. A subpopulation of preganglionic inputs to noradrenergic MPG neurons also showed CGRP immunoreactivity. Together, these studies reveal new molecular and structural features of the pelvic nerves and suggest functional targets of sensory nerves in the MPG. These anatomical data will facilitate the design of experimental bioengineering strategies to specifically modulate each axon class.

Neural interrelationships of autonomic ganglia from the pelvic region of male rats

The aims of the present study were to describe, in male rats, the anatomical organization of the major and accessory pelvic ganglia (MPG, AG; respectively), the interrelationship of the pelvic plexus components, and the morphometry of the pelvic postganglionic neurons. Anatomical, histochemical and histological studies were performed in anesthetized adult Wistar male rats. We found that the pelvic plexus consists of intricate neural circuits composed of two MPG, and three pairs of AG (AGI, AGII, AGIII) anatomically interrelated through ipsilateral and contralateral commissural nerves. Around 30 nerves emerge from each MPG and 17 from AGI and AGII. The MPG efferent nerves spread out preganglionic information to several pelvic organs controlling urinary, bowel, reproductive and sexual functions, while AG innervation is more regional, and it is confined to reproductive organs located in the rostral region of the urogenital tract. Both MPG and AG contain nerve fascicles, blood vessels, small intensely fluorescent cells, satellite cells and oval neuronal somata with one to three nucleoli. The soma area of AG neurons is larger than those of MPG neurons (p < 0.005). The MPG contains about 75% of the total pelvic postganglionic neurons. Our findings corroborated previous reports about MPG inputs, and add new information regarding pelvic ganglia efferent branches, AG neurons (number and morphometry), and neural interrelationship between the pelvic plexus components. This information will be useful in designing future studies about the role of pelvic innervation in the physiology and pathophysiology of pelvic functions.

Pelvic and hypogastric nerves are injured in a rat prostatectomy model, contributing to development of stress urinary incontinence

Urinary incontinence affects 40% of elderly men, is common in diabetic patients and in men treated for prostate cancer, with a prevalence of up to 44%. Seventy-two percent of prostatectomy patients develop stress urinary incontinence (SUI) in the first week after surgery and individuals who do not recover within 6 months generally do no regain function without intervention. Incontinence has a profound impact on patient quality of life and a critical unmet need exists to develop novel and less invasive SUI treatments. During prostatectomy, the cavernous nerve (CN), which provides innervation to the penis, undergoes crush, tension, and resection injury, resulting in downstream penile remodeling and erectile dysfunction in up to 85% of patients. There are other nerves that form part of the major pelvic ganglion (MPG), including the hypogastric (HYG, sympathetic) and pelvic (PN, parasympathetic) nerves, which provide innervation to the bladder and urethra. We examine if HYG and PNs are injured during prostatectomy contributing to SUI, and if Sonic hedgehog (SHH) regulatory mechanisms are active in the PN and HYG nerves. CN, PN, HYG and ancillary (ANC) of uninjured, sham and CN crush/MPG tension injured (prostatectomy model) adult Sprague Dawley rats (n = 37) were examined for apoptosis, sonic hedgehog (SHH) pathway, and intrinsic and extrinsic apoptotic mechanisms. Fluorogold tracing from the urethra/bladder was performed. PN and HYG response to SHH protein was examined in organ culture. TUNEL, immunohistochemical analysis for caspase-3 cleaved, -8, -9, SHH, Patched and Smoothened (SHH receptors), and neurite formation, were examined. Florogold positive neurons in the MPG were reduced with CN crush. Apoptosis increased in glial cells of the PN and HYG after CN crush. Caspase 9 was abundant in glial cells (intrinsic), while caspase-8 was not observed. SHH and its receptors were abundant in neurons and glia of the PN and HYG. SHH treatment increased neurite formation. PN and HYG injury occur concomitant with CN injury during prostatectomy, likely contributing to SUI. PN and HYG response to SHH treatment indicates an avenue for intervention to promote regeneration and prevent SUI.

Visualization of prostatic nerves by polarization-sensitive optical coherence tomography

Preservation of prostatic nerves is critical to recovery of a man's sexual potency after radical prostatectomy. A real-time imaging method of prostatic nerves will be helpful for nerve-sparing radical prostatectomy (NSRP). Polarization-sensitive optical coherence tomography (PS-OCT), which provides both structural and birefringent information of tissue, was applied for detection of prostatic nerves in both rat and human prostate specimens, ex vivo. PS-OCT imaging of rat prostate specimens visualized highly scattering and birefringent fibrous structures superficially, and these birefringent structures were confirmed to be nerves by histology or multiphoton microscopy (MPM). PS-OCT could easily distinguish these birefringent structures from surrounding other tissue compartments such as prostatic glands and fats. PS-OCT imaging of human prostatectomy specimens visualized two different birefringent structures, appearing fibrous and sheet-like. The fibrous ones were confirmed to be nerves by histology, and the sheet-like ones were considered to be fascias surrounding the human prostate. PS-OCT imaging of human prostatectomy specimens along the perimeter showed spatial variation in the amount of birefringent fibrous structures which was consistent with anatomy. These results demonstrate the feasibility of PS-OCT for detection of prostatic nerves, and this study will provide a basis for intraoperative use of PS-OCT.

Inhibitory effects of tibial nerve stimulation on bladder neurophysiology in rats

Tibial nerve stimulation (TNS) is a form of peripheral neuromodulation which has been found effective in treating overactive bladder symptoms, with lesser side effects than first line pharmacotherapy. Despite its widespread clinical use, the underlying mechanism of action is not fully understood. Our aim was to study its effect on the bladder neurophysiology and the trigger mechanism of voiding in the overactive detrusor, simulated by acetic acid (AA) instillation. In urethane anaesthetized male Wistar rats, the tibial nerve was stimulated for 30 min at 5 Hz, pulse width 200 µs and amplitude approximately three times the threshold to induce a slight toe movement. The pressure at which a voiding contraction was triggered (pthres) did not change significantly between the pre- and post-TNS measurements in AA induced detrusor overactivity. It was found that TNS significantly reversed the effects of AA irritation by increasing the bladder compliance and the bladder volume at pthres, as well as suppressed the threshold afferent nerve activity. The slope of the linear relationship between pressure and the afferent activity increased after AA instillation and decreased significantly after stimulation. In addition to its well-known central inhibitory mechanisms, this study has demonstrated that TNS improves bladder storage capacity by delaying the onset of voiding, via an inhibitory effect on the bladder afferent signaling at the peripheral level.

Neurogenic mechanisms in bladder and bowel ageing

The prevalence of both urinary and faecal incontinence, and also chronic constipation, increases with ageing and these conditions have a major impact on the quality of life of the elderly. Management of bladder and bowel dysfunction in the elderly is currently far from ideal and also carries a significant financial burden. Understanding how these changes occur is thus a major priority in biogerontology. The functions of the bladder and terminal bowel are regulated by complex neuronal networks. In particular neurons of the spinal cord and peripheral ganglia play a key role in regulating micturition and defaecation reflexes as well as promoting continence. In this review we discuss the evidence for ageing-induced neuronal dysfunction that might predispose to neurogenic forms of incontinence in the elderly.

Novel therapeutic approach for neurogenic erectile dysfunction: effect of neurotrophic tyrosine kinase receptor type 1 monoclonal antibody

BACKGROUND

Erectile dysfunction (ED) is a major health issue in aged populations, and neurogenic ED is particularly difficult to treat. Novel therapeutic approaches are needed for treatment of neurogenic ED of peripheral origin.

OBJECTIVE

To investigate the therapeutic effects of a neurotrophic tyrosine kinase receptor type 1 monoclonal antibody (TrkA-mAb) on erectile function and sexual behavior in a rat model of cavernous nerve injury (CNI).

DESIGN, SETTING, AND PARTICIPANTS

In one experiment, 84 male rats were randomly assigned to seven groups. The groups underwent either CNI or sham surgery, subsequent injection into the major pelvic ganglion (IMPG) of phosphate-buffered saline (PBS), an immunoglobulin G (IgG) control, or TrkA-mAb, and then intracavernosal (IC) injection of either PBS or varying TrkA-mAb concentrations immediately after surgery and then 1 wk later. Erectile function was assessed and histologic/molecular analyses were performed at 6 wk after surgery. In a second experiment, 36 male rats were randomly divided into three groups. The groups underwent CNI or sham surgery and then IC injection of PBS, IgG, or TrkA-mAb immediately after surgery and for 5 wk thereafter. At 6 wk after surgery, the performance of the rats in sexual behavior tests was videotaped.

INTERVENTION

CNI or sham surgery; IMPG of PBS, IgG, or TrkA-mAb; IC injection of PBS or TrkA-mAb.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The intracavernous pressure response to cavernous nerve electrostimulation was measured and midpenile cross-sections were histologically examined. Western blotting (WB) of cavernous tissue protein was performed. Rats were assessed for chasing, mounting, intromission, and ejaculation behaviors during sexual behavior tests. The data were analyzed using one-way analysis of variance followed by the Tukey-Kramer t test.

RESULTS AND LIMITATIONS

Recovery of erectile function of varying degrees was observed in the TrkA-mAb groups. TrkA-mAb treatment significantly suppressed tyrosine hydroxylase-positive nerve fibers in the corpus cavernosum and enhanced neuronal nitric oxide synthase-positive fibers in the dorsal nerve. The ratio of smooth muscle to collagen in the corpus cavernosum was significantly improved in TrkA-mAb treatment groups compared to PBS vehicle and IgG control groups. WB confirmed these biological changes. There was a nonsignificant increase in the average number of intromissions and ejaculations in the TrkA-mAb group. The study limitations include small sample size, variability in sexual behavior, lack of data on the neuromuscular mechanism involved, and lack of information of the role of neurotrophins or cytokines in regeneration.

CONCLUSIONS

TrkA-mAb successfully inhibits sympathetic nerve regeneration, leads to parasympathetic nerve regeneration, and has therapeutic effects on ED and sexual behavior disorder in a rat model of CNI.

PATIENT SUMMARY

This report provides strong evidence that a neurotrophic tyrosine kinase receptor type 1 monoclonal antibody (TrkA-mAb) inhibits sympathetic nerve regeneration, leads to parasympathetic nerve regeneration, and has therapeutic effects on erectile dysfunction and sexual behavior disorder in a rat model of cavernous nerve injury. The results raise the possibility that human patients with neurogenic erectile dysfunction may respond to TrkA-mAb in a manner that parallels the response seen in our rodent study.

Immunohistochemical characteristics and distribution of neurons in the paravertebral, prevertebral and pelvic ganglia supplying the urinary bladder in the male pig

The distribution and chemical coding of neurons supplying urinary bladder in the male pig were studied in the sympathetic chain ganglia, inferior mesenteric ganglia and anterior pelvic ganglia. The combined retrograde tracing and immunohistochemistry for tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), neuropeptide Y (NPY), somatostatin(SOM), galanin (GAL), vasoactive intestinal polypeptide(VIP), nitric oxide synthase (NOS), calcitonin gene related peptide (CGRP), substance P (SP), choline acetyltransferase (ChAT) and vesicular acetylcholine transporter(VAChT) were applied in the experiment. Bladder projecting neurons were found in all the ganglia studied. The majority of sympathetic ganglia neurons (inferior mesenteric ganglia and sympathetic chain ganglia) expressed immunoreactivity(IR) to DBH. In sympathetic chain ganglia these neurons simultaneously expressed NPY, GAL or VAChT,while in inferior mesenteric ganglia they contained NPY, SOM and/or GAL. A small number of these bladder projecting neurons was VAChT-IR and some contained NPY. In the pelvic ganglia bladder-projecting neurons formed two populations: DBH- and VAChT-IR. Some of DBH-IR neurons contained IR to NPY, SOM or GAL, while VAChTIR neurons were NPY-, SOM- or NOS-IR. The results indicate that sympathetic ganglia contain mainly adrenergic neurons,while pelvic ganglia contain both adrenergic and cholinergic neurons. All these neurons contain typical combinations of neuropeptides.

Excitatory GABAA receptor in autonomic pelvic ganglion neurons innervating bladder

Major pelvic ganglia (MPG) are relay centers for autonomic reflexes such as micturition and penile erection. MPG innervate the urogenital system, including bladder. γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and may also play an important role in some peripheral autonomic ganglia, including MPG. However, the electrophysiological properties and function of GABAA receptor in MPG neurons innervating bladder remain unknown. This study examined the electrophysiological properties and functional roles of GABAA receptors in bladder-innervating neurons identified by retrograde Dil tracing. Neurons innervating bladder showed previously established parasympathetic properties, including small membrane capacitance, lack of T-type Ca(2+) channel expression, and tyrosine-hydroxylase immunoreactivity. GABAA receptors were functionally expressed in bladder innervating neurons, but GABAC receptors were not. GABA elicited strong depolarization followed by increase of intracellular Ca(2+) in neurons innervating bladder, supporting the hypothesis GABA may play an important role in bladder function. These results provide useful information about the autonomic function of bladder in physiological and pathological conditions.

The concept of peripheral modulation of bladder sensation

It is recognized that, as the bladder fills, there is a corresponding increase in sensation. This awareness of the volume in the bladder is then used in a complex decision making process to determine if there is a need to void. It is also part of everyday experience that, when the bladder is full and sensations strong, these sensations can be suppressed and the desire to void postponed. The obvious explanation for such altered perceptions is that they occur centrally. However, this may not be the only mechanism. There are data to suggest that descending neural influences and local factors might regulate the sensitivity of the systems within the bladder wall generating afferent activity. Specifically, evidence is accumulating to suggest that the motor-sensory system within the bladder wall is influenced in this way. The motor-sensory system, first described over 100 years ago, appears to be a key component in the afferent outflow, the afferent "noise," generated within the bladder wall. However, the presence and possible importance of this complex system in the generation of bladder sensation has been overlooked in recent years. As the bladder fills the motor activity increases, driven by cholinergic inputs and modulated, possibly, by sympathetic inputs. In this way information on bladder volume can be transmitted to the CNS. It can be argued that the ability to alter the sensitivity of the mechanisms generating the motor component of this motor-sensory system represents a possible indirect way to influence afferent activity and so the perception of bladder volume centrally. Furthermore, it is emerging that the apparent modulation of sensation by drugs to alleviate the symptoms of overactive bladder (OAB), the anti-cholinergics and the new generation of drugs the β 3 sympathomimetics, may be the result of their ability to modulate the motor component of the motor sensory system. The possibility of controlling sensation, physiologically and pharmacologically, by influencing afferent firing at its point of origin is a "new" concept in bladder physiology. It is one that deserves careful consideration as it might have wider implications for our understanding of bladder pathology and in the development of new therapeutic drugs. In this overview, evidence for the concept peripheral modulation of bladder afferent outflow is explored.

Culture of major pelvic ganglion neurons from adult rat

Successful culturing of neurons from adult animals has been historically difficult for a relatively long time. In this study, we reported the development of a novel method for the isolation and the culture of major pelvic ganglion (MPG) neurons from adult rat. The cultured cells were identified by neuron morphology and staining with neuronal marker (neurofilament-200, NF-200). The results demonstrate that the new protocol we used was reliable in obtaining a relatively high yield of MPG neurons. Furthermore, it improves the speed and simplicity in neuronal isolation. The viability of neurons can be maintained for about 2 weeks, which should be sufficient for investigating physiological and pathological processes occurring in mature major pelvic ganglia. And this may provide a useful assessment to currently available techniques for the culture of adult neurons.

Autonomic dysfunction and plasticity in micturition reflexes in human α-synuclein mice

Although often overshadowed by the motor dysfunction associated with Parkinson's disease (PD), autonomic dysfunction including urinary bladder and bowel dysfunctions are often associated with PD and may precede motoric changes; such autonomic dysfunction may permit early detection and intervention. Lower urinary tract symptoms are common in PD patients and result in significant morbidity. This studies focus on nonmotor symptoms in PD using a transgenic mouse model with overexpression of human α-synuclein (hSNCA), the peptide found in high concentrations in Lewy body neuronal inclusions, the histopathologic hallmark of PD. We examined changes in the physiological, molecular, chemical, and electrical properties of neuronal pathways controlling urinary bladder function in transgenic mice. The results of these studies reveal that autonomic dysfunction (i.e., urinary bladder) can precede motor dysfunction. In addition, mice with hSNCA overexpression in relevant neuronal populations is associated with alterations in expression of neurotransmitter/neuromodulatory molecules (PACAP, VIP, substance P, and neuronal NOS) within neuronal pathways regulating bladder function as well as with increased NGF expression in the urinary bladder. Changes in the electrical and synaptic properties of neurons in the major pelvic ganglia that provide postganglionic innervation to urogenital tissues were not changed as determined with intracellular recording. The urinary bladder dysfunction observed in transgenic mice likely reflects changes in peripheral (i.e., afferent) and/or central micturition pathways or changes in the urinary bladder. SYN-OE mice provide an opportunity to examine early events underlying the molecular and cellular plasticity of autonomic nervous system pathways underlying synucleinopathies.

The soma and proximal dendrites of sympathetic preganglionic neurons innervating the major pelvic ganglion in female rats receive predominantly inhibitory inputs

Sympathetic preganglionic neurons (SPNs) in the intermediolateral (IML) and dorsal commissural nucleus (DCN) of the thoracolumbar segments of the spinal cord contribute to the autonomic control of the pelvic visceral organs. We examined the morphology of these neurons at the light and electron microscopic level and quantified the boutons apposing the soma and proximal dendrites of the SPNs innervating the major pelvic ganglion (MPG) in female rats. The majority of these cells resided in the DCN (61.6±6.2%) and IML (33.2±4.4%) nuclei. Measurements of cell volume and shape revealed no differences between SPNs sampled from the DCN and IML populations. Ultrastructural studies of DCN and IML SPNs revealed that coverage of SPNs by synaptic inputs is sparse, with an average of 11.60±2.41% of the soma membrane and 16.33±6.18% of proximal dendrites apposed by boutons, though some somata exhibited no synaptic coverage. Three distinct types of boutons were found to appose the SPN somata and dendrites. The putatively inhibitory F-type bouton covered a significantly greater percentage of membrane on the soma (8.48±2.12%) and dendrites (12.65±4.34%), than the S-type bouton, a putatively excitatory bouton, which only covered 2.94±0.70% of the somatic and 3.68±2.98% of the dendritic membranes. Boutons with dense-core vesicles were rare. Our results demonstrate that SPNs of the DCN and IML of female rats are similar morphologically, and that synaptic input on these cells, though sparse, is predominantly inhibitory.

Imaging guidance in minimally invasive prostatectomy

Minimally invasive prostatectomy, such as laparoscopic and robot-assisted prostatectomy, has become more popular, with similar short-term outcomes as open radical retropubic prostatectomy series. The purpose of this article is to review different imaging modalities that have been developed with a goal of further improving the surgical outcomes in minimally invasive prostatectomy.

The influence of ileitis on the neurochemistry of the caudal mesenteric ganglion in the pig

BACKGROUND

Some literature data suggest that there is a regulatory neuronal circuit between the small and the large bowel. To verify this hypothesis the present study investigated: (i) the distribution, chemical coding and routing of caudal mesenteric ganglion (CaMG) neurons participating in an intestinointestinal reflex pathway involving ileal descending neurons and viscerofugal colonic neurons and (ii) possible changes in the neuroarchitecture of this pathway evoked by chemically induced ileitis in juvenile pigs (n=16).

METHODS

Combined retrograde tract tracing and transections of the intermesenteric or caudal colonic nerves were applied. In addition, double immunostainings was used to investigate the chemical coding of retrogradely labeled CaMG neurons and intraganglionic nerve terminals apposed to them, under normal and inflammatory conditions.

KEY RESULTS

The majority of the ileum-projecting neurons were found in the caudal part of CaMG. Disruption of particular nerve pathways resulted in diminished number of retrogradely labeled neurons, ipsilateral to the side of manipulation. In normal pigs, ileum-projecting CaMG neurons stained for tyrosine hydroxylase, dopamine-β-hydroxylase, neuropeptide Y (NPY), somatostatin and galanin (GAL). The number and chemical coding of the neurons in the inflamed animals were similar to those observed in the normal pigs. However, in the inflamed pigs, the number of NPY-, GAL- or substance P-positive nerve terminals supplying retrogradely labeled neurons was increased.

CONCLUSIONS & INFERENCES

The present results suggest that inflammatory processes of the porcine ileum are able to induce changes in the intraganglionic architecture of a sympathetic ganglion located at discrete distance from the affected bowel segment.

Distribution pattern and chemical coding of neurons of the sympathetic chain ganglia supplying the descending colon in the pig

Sympathetic chain ganglia (SChG) neurons projecting to the descending colon of the pig were studied by means of retrograde tracing (Fast Blue, FB) and double-labelling immunofluorescence methods. FB was injected into the gut wall and after three weeks survival time the animals were transcardially perfused with paraformaldehyde and the bilateral sympathetic trunks were collected. The FB-positive neurons were localised only in the lumbar (L(1)-L(5)) ganglia of the sympathetic trunk and appeared either as small (30-50 microm in diameter) round-shaped perikarya forming clusters localised in caudal-ventral area or, rarely, as bigger (50-80 microm) and dispersed solitary irregular perikarya. Immunohistochemical staining revealed the catecholaminergic (tyrosine hydroxylase-/dopamine beta-hydroxylase-immunoreactive) character of the great majority of FB-positive neurons which preferentially co-expressed neuropeptide Y. In addition, none of the FB-positive perikarya was immunopositive to galanin, somatostatin, choline acetyltransferase, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, leu(5)-enkephalin, nitric oxide synthase, substance P and calcitonin-generelated peptide.

Anatomical tracer injections into the lower urinary tract may compromise cystometry and external urethral sphincter electromyography in female rats

Physiological and anatomical investigations are commonly combined in experimental models. When studying the lower urinary tract (LUT), it is often of interest to perform both urodynamic studies and retrogradely labeled neurons innervating the peripheral target organs. However, it is not known whether the use of anatomical tracers for the labeling of, e.g. spinal cord neurons may interfere with the interpretation of the physiological studies on micturition reflexes. We performed cystometry and external urethral sphincter (EUS) electromyography (EMG) under urethane anesthesia in adult female rats at 5-7 days after injection of a 5% fluorogold (FG) solution or vehicle into the major pelvic ganglia (MPG) or the EUS. FG and vehicle injections into the MPG and EUS resulted in decreased voiding efficiency. MPG injections increased the duration of both bladder contractions and the inter-contractile intervals. EUS injections decreased EUS EMG bursting activity during voiding as well as increased both the duration of bladder contractions and the maximum intravesical pressure. In addition, the bladder weight and size were increased after either MPG or EUS injections in both the FG and vehicle groups. We conclude that the injection of anatomical tracers into the MPG and EUS may compromise the interpretation of subsequent urodynamic studies and suggest investigators to consider experimental designs, which allow for physiological assessments to precede the administration of anatomical tracers into the LUT.

Fiberoptic imaging of cavernous nerves in vivo

PURPOSE

A critical intraoperative variable for the return of tumescence following radical prostatectomy is preservation of the cavernous nerves. We developed a nontoxic technique that would allow high resolution, in vivo real-time imaging specifically of the cavernous nerves.

MATERIALS AND METHODS

The cavernous nerves were labeled by injecting a fluorescent retrograde nerve tracer into the corpus cavernosum of male rats. Nerves were subsequently imaged in vivo using fiberoptic confocal fluorescent microscopy. Initial screening trials were performed to decide on a nerve tracer capable of axonal labeling, optimize injection concentration and characterize retrograde transport time. Toxicity studies included intracavernous pressure monitoring following electrical nerve stimulation, apoptotic staining of injected cavernous tissue and measurement of lipid peroxidation in nerves exposed to laser emissions during imaging.

RESULTS

In vivo real-time video sequences of fluorescently labeled cavernous nerves were recorded. The screening trial indicated that the B subunit of cholera toxin conjugated to AlexaFluor 488 (Invitrogen) provided optimal imaging after 9 days of retrograde transport. Toxicity studies showed that maximal intracavernous pressure responses did not differ between labeled and unlabeled nerves (p = 0.9671). Tracer injection did not increase apoptosis in cavernous tissue and laser exposure did not increase lipid peroxidation in nerves.

CONCLUSIONS

In vivo real-time imaging of the cavernous nerves is possible with no measurable toxicity, allowing the maintenance of erection. This novel imaging modality may allow urologists to identify cavernous nerves during pelvic surgery.

Mesenteric transection decreases expression of interstitial cells of Cajal in an experimental model

Background

After anterior resection for rectal carcinoma patients often complain of defaecatory dysfunction. The aim of this study was to examine the number of interstitial cells of Cajal (ICCs) and ganglion cells in the distal colon partially denervated by mesenteric transection in a rat model.

Methods

Four groups of rats were operated on, a control group and three experimental groups, with increasing degree of mesenteric transection to denervate the distal colon. Animals were killed after 3 months, and the denervated colon was investigated using immunohistochemistry with Kit and protein gene product 9.5 antibodies to detect ICCs and ganglion cells respectively. Reverse transcriptase–polymerase chain reaction for c-kit and histomorphometry of muscular thickness were performed.

Results

The total number of ICCs was significantly lower in the three operated models than in the control, particularly in the histological layers of the myenteric plexus and submucosal border. There was no difference in the number of ganglion cells or changes in muscular thickness between the models.

Conclusion

The number of ICCs in rat distal colon denervated by mesenteric transection is decreased at 3 months after surgery.

Comparison of extrinsic efferent innervation of guinea pig distal colon and rectum

The extrinsic efferent innervation of the distal colon and rectum of the guinea pig was compared, by using retrograde tracing combined with immunohistochemistry. Application of the carbocyanine tracer DiI to the rectum filled significantly greater numbers of extrinsic neurons than similar injections into the distal colon. Approximately three-fourths of all filled neurons from either location were either sympathetic or parasympathetic; the rest were spinal sensory neurons. Nerve cell bodies in sympathetic prevertebral ganglia labelled from the two regions were similar in number. Both regions were innervated by sympathetic neurons in paravertebral ganglia; however, the rectum received much more input from this source than the colon. The rectum received significantly more input from pelvic ganglia than the colon. The rectum also received direct innervation from two groups of neurons in the spinal cord. Neurons located in the spinal parasympathetic nucleus in segment S2 and S3 were labelled by DiI injected into the rectal wall. Similar numbers of neurons, located in intermediolateral cell column and dorsal commissural nucleus of lumbar segments, also projected directly to rectum, but not colon. The great majority (>80%) of retrogradely labelled nerve cell bodies in sympathetic ganglia were immunoreactive for tyrosine hydroxylase. In pelvic ganglia, retrogradely labelled neurons contained choline acetyltransferase and/or nitric oxide synthase or tyrosine hydroxylase. Although the rectum and colon in this species are continuous and macroscopically indistinguishable, they have significantly different patterns of extrinsic efferent innervation, presumably reflecting their different functions.

Structural effects and potential changes in growth factor signalling in penis-projecting autonomic neurons after axotomy

Background

The responses of adult parasympathetic ganglion neurons to injury and the neurotrophic mechanisms underlying their axonal regeneration are poorly understood. This is especially relevant to penis-projecting parasympathetic neurons, which are vulnerable to injury during pelvic surgery such as prostatectomy. We investigated the changes in pelvic ganglia of adult male rats in the first week after unilateral cavernous (penile) nerve axotomy (cut or crush lesions). In some experiments FluoroGold was injected into the penis seven days prior to injury to allow later identification of penis-projecting neurons. Neurturin and glial cell line-derived neurotrophic factor (GDNF) are neurotrophic factors for penile parasympathetic neurons, so we also examined expression of relevant receptors, GFRα1 and GFRα2, in injured pelvic ganglion neurons.

Results

Axotomy caused prolific growth of axon collaterals (sprouting) in pelvic ganglia ipsilateral to the injury. These collaterals were most prevalent in the region near the exit of the penile nerve. This region contained the majority of FluoroGold-labelled neurons. Many sprouting fibres formed close associations with sympathetic and parasympathetic pelvic neurons, including many FluoroGold neurons. However immunoreactivity for synaptic proteins could not be demonstrated in these collaterals. Preganglionic terminals showed a marked loss of synaptic proteins, suggesting a retrograde effect of the injury beyond the injured neurons. GFRα2 immunofluorescence intensity was decreased in the cytoplasm of parasympathetic neurons, but GFRα1 immunofluorescence was unaffected in these neurons.

Conclusion

These studies show that there are profound changes within the pelvic ganglion after penile nerve injury. Sprouting of injured postganglionic axons occurs concurrently with structural or chemical changes in preganglionic terminals. New growth of postganglionic axon collaterals within the ganglion raises the possibility of the formation of aberrant synaptic connections between injured and un-injured ganglion neurons. Together these changes demonstrate a broader effect on the pelvic autonomic circuitry than simply loss of neuroeffector connections. These structural changes are accompanied by potential changes in neurotrophic factor signalling due to altered expression of receptors for members of the GDNF family. Together our results advance understanding of the responses of pelvic autonomic nerve circuits to injury and may assist in designing strategies for promoting regeneration.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Anatomical evidence for glutamatergic transmission in primary sensory neurons and onto postganglionic neurons controlling penile erection in rats: an ultrastructural study with neuronal tracing and immunocytochemistry

In male rats, the dorsal penile nerve (DPN) conveys sensory information from the genitals to the lumbosacral spinal segments of the spinal cord. DPN is the afferent limb of a reflex loop that supports reflexive erections, and that includes a network of spinal interneurons and autonomic and somatic motoneurons to the penis and perineal striated muscles. Autonomic efferent pathways to the penis relay in the major pelvic ganglion (MPG). Glutamate (Glu) is a likely candidate as a neurotransmitter of reflexive erections. Both AMPA and NMDA glutamatergic receptor subunits are present in the lumbosacral spinal cord, and AMPA and NMDA receptor antagonists block reflexive erections. In the present study, we used tract-tracing experiments combined with immunohistochemical and immunocytochemical techniques to ascertain the presence of Glu at two different levels of the network controlling reflexive erections. DPN afferents were localized in the dorsal horn of the lumbosacral cord and displayed the characteristics of either C-fibers or Adelta fibers. DPN terminals (some of them glutamatergic) were mainly distributed in the medial edge of the dorsal horn in the L6 spinal segment. GluR1 subunits were present in some DPN afferents, suggesting that they could be autoreceptors. DPN fibers were also present in the MPG, as were Glu terminals and GluR4 subunits. The results reveal the presence of Glu in DPN fibers and terminals and suggest that both the spinal cord and the MPG use glutamatergic transmission to control reflexive erections.

Distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)-expressing cells in rat urinary bladder: a developmental study

We examined the distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)(55-102)-immunoreactive (IR) structures in the neonatal and adult rat urinary bladder. Double-labeling studies examining CARTp with tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), or choline acetyltransferase (ChAT) were performed in wholemounts of urothelium or detrusor or cryostat sections of the bladder. In younger animals (postnatal day [P]1, P3), CARTp-IR cell bodies in detrusor smooth muscle were observed in large clusters ( approximately 100 cells/cluster) at the ureteral insertion and along thick bundles of nerve fibers at the bladder base. The total number of CARTp-IR cells was significantly reduced (by five-fold) at P14, and this reduced number persisted into adulthood. The decrease in the number of CARTp-expressing cells was complemented with positive staining for cleaved caspase-3, suggesting that apoptosis contributed to this decrease. At birth (P1), all CARTp-IR cells expressed the neuronal marker Hu. After birth, CARTp was expressed by some neurons (CARTp-IR, Hu-IR) that represent intramural ganglion cells and by cells that lacked a neuronal phenotype (CARTp-IR, Hu-) but did express TH. Neither of these cell populations expressed ChAT immunoreactivity in adult bladder. These cells (CARTp-IR, Hu-, TH-IR) may represent paraganglion or small intensely fluorescent (SIF) cells. The percentage of colocalization of CARTp-IR and nNOS or TH was dependent on postnatal age and showed an inverse relationship. At P1, 67.1 % of CARTp-IR cells expressed nNOS immunoreactivity. Decreased colocalization was observed with increasing postnatal age. In contrast, 19.5% of CARTp-IR cells expressed TH at P1, but colocalization increased with postnatal age. The suburothelial plexus lacked CARTp-IR nerve fibers until P14, when nerve fibers with varicosities were observed in the urethra and bladder neck region. In summary, we demonstrate 1) a decrease in the number of CARTp-IR cells in rat detrusor in early postnatal development; 2) apoptotic events in the bladder during early postnatal development; 3) rostral migration of CARTp-IR cells from the ureteral insertion toward the bladder body during postnatal development; 4) the presence of different populations of CARTp-IR cells, some with and others without a neuronal phenotype; and (5) age-dependent changes in chemical coding of CARTp-IR cells with postnatal development. This study demonstrates that CARTp-IR intramural ganglia and CARTp-IR paraganglion or SIF cells exist in the postnatal and adult rat bladder, although the role of these cell types remains to be determined.

CYCLOPHOSPHAMIDE INDUCED CYSTITIS ALTERS NEUROTROPHIN AND RECEPTOR TYROSINE KINASE EXPRESSION IN PELVIC GANGLIA AND BLADDER

PURPOSE

We examined neurotrophin and receptor tyrosine kinase (Trk) expression in the bladder and major pelvic ganglia (MPG) after cyclophosphamide induced cystitis in rats.

MATERIALS AND METHODS

The bladder and MPG were used in immunohistochemical studies, enzyme-linked immunoassays and Western blots for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), TrkA and TrkB. Bladder postganglionic MPG cells were labeled by tracing techniques.

RESULTS

NGF and BDNF expression was decreased in the bladder of all rats after cystitis (p < or =0.001). NGF and BDNF expression was increased in the MPG in male rats with cystitis (p < or =0.01). Cells expressing TrkA and TrkB immunoreactivity (IR) increased 78% to 81% in the MPG in male rats with cystitis. TrkA-IR or TrkB-IR bladder postganglionic cells increased 50% to 74% with cystitis. Cystitis increased TrkA-IR 5 to 10-fold and TrkB-IR 10 to 12-fold in detrusor muscle. TrkA-IR and TrkB-IR were prominent in control urothelium but decreased with cystitis. After cystitis TrkB-IR nerve fibers and TrkA-IR cellular infiltrates were more apparent compared to controls.

CONCLUSIONS

Cystitis decreases bladder NGF and BDNF expression, whereas MPG expression is increased. This change may reflect neurotrophin release at the bladder and retrograde transport to the MPG. TrkA-IR and TrkB-IR are increased in bladder postganglionic cells and bladders with cystitis. This increase may reflect a shift in Trk staining from urothelium to detrusor muscle and nerve fibers with cystitis. Neurotrophin/Trk interactions in the bladder and MPG may contribute to bladder overactivity with cystitis.

Characterization of the primary spinal afferent innervation of the mouse colon using retrograde labelling

Visceral pain is the most common form of pain produced by disease and is thus of interest in the study of gastrointestinal (GI) complaints such as irritable bowel syndrome, in which sensory signals perceived as GI pain travel in extrinsic afferent neurones with cell bodies in the dorsal root ganglia (DRG). The DRG from which the primary spinal afferent innervation of the mouse descending colon arises are not well defined. This study has combined retrograde labelling and immunohistochemistry to identify and characterize these neurones. Small to medium-sized retrogradely labelled cell bodies were found in the DRG at levels T8-L1 and L6-S1. Calcitonin gene-related peptide (CGRP)- and P2X3-like immunoreactivity (LI) was seen in 81 and 32%, respectively, of retrogradely labelled cells, and 20% bound the Griffonia simplicifolia-derived isolectin IB4. CGRP-LI and IB4 were co-localized in 22% of retrogradely labelled cells, whilst P2X3-LI and IB4 were co-localized in 7% (vs 34% seen in the whole DRG population). Eighty-two per cent of retrogradely labelled cells exhibited vanilloid receptor 1-like immunoreactivity (VR1-LI). These data suggest that mouse colonic spinal primary afferent neurones are mostly peptidergic CGRP-containing, VR1-LI, C fibre afferents. In contrast to the general DRG population, a subset of neurones exist that are P2X3 receptor-LI but do not bind IB4.

Estrogen receptor expression in lumbosacral dorsal root ganglion cells innervating the female rat urinary bladder

We have investigated whether bladder afferent neurons are likely to be targets for circulating estrogens by mapping estrogen receptor (ER) distribution in lumbosacral dorsal root ganglia (DRG) of adult female rats. Sensory neurons innervating either the detrusor or trigone regions were identified by application of fluorescent retrograde tracer dyes to the bladder wall. Labelled neurons were classified by their immunoreactivity for either type of ER (ERalpha or ERbeta) and further compared with subpopulations of neurons containing substance P, calcitonin gene-related peptide and vanilloid receptor (a marker of polymodal nociceptors). Both ER types were expressed in numerous sensory neurons of either upper lumbar (L1/L2) or lower lumbar/sacral (L6/S1) ganglia and there was almost complete coexpression of ERalpha and ERbeta. ER-positive neurons were mainly small-medium size (18-25-microm diameter), indicating that they may be nociceptors and/or supply visceral targets. Most bladder-projecting neurons expressed ERs and the majority of these also expressed neuropeptides or vanilloid receptor. Afferent neurons supplying detrusor and trigone regions had similar immunohistochemical features. About a third of the bladder-projecting neurons expressed both ER and vanilloid receptor, suggesting a mechanism by which estrogens could influence bladder pain. The prevalence of different chemical classes of ER-positive bladder-projecting neurons was reflected throughout the entire population of neurons in dorsal root ganglia of these spinal levels, suggesting that neurons supplying other pelvic visceral targets may have similar chemical profiles. These results suggest that many functional classes of sensory neurons innervating the lower urinary tract are likely to be targets for circulating estrogens, including many nociceptor neurons. The coexistence of ERalpha and ERbeta suggests a broad range of potential mechanisms by which estrogens may exert their genomic effects in this system.

Nicotinic transmission at functionally distinct synapses in descending reflex pathways of the rat colon

We examined descending reflex pathways in the rat colon using intracellular recording techniques. Inhibitory junction potentials (IJPs) were recorded from circular smooth muscle when descending pathways were excited by combined mucosal compression and distension. IJPs were reduced to 71% of control when synaptic transmission was blocked in the oral stimulation chamber of a divided organ bath suggesting that two reflex pathways exist, the one involving descending sensory neurones and the other involving descending interneurones. Hexamethonium (200 micromol L(-1)) in the recording chamber abolished reflexly evoked IJPs, while in the stimulation chamber, it was as effective as synaptic blockade. When hexamethonium was added to a chamber lying between the stimulation and recording chambers, it again sharply depressed IJPs to 27% of control; an extent similar to synaptic blockade. A P2 receptor antagonist did not reveal any purinergic neurotransmission. Either granisetron (5-HT3 receptor antagonist, 1 micromol L(-1)) or SB204070 (5-HT4 receptor antagonist, 1 micromol L(-1)) in the stimulation chamber significantly decreased IJPs; these decreases were not additive. We conclude that some sensory neurones and interneurones in rat colon have long anally projecting axons and that acetylcholine, acting via nicotinic receptors, is the primary neurotransmitter from sensory neurones, to inhibitory motor neurones and between interneurones.

Spatial segregation within the sacral parasympathetic nucleus of neurons innervating the bladder or the penis of the rat as revealed by three-dimensional reconstruction

The purpose of the present investigations was (1) to examine the spatial organization of preganglionic neurons of the sacral parasympathetic nucleus in the lumbosacral spinal cord of male adult rats and (2) to search, in this nucleus, for a possible segregation of sub-populations of neurons innervating the penis or the bladder, respectively. To estimate their spatial organization, neurons of the sacral parasympathetic nucleus were retrogradely labeled by wheat germ agglutinin coupled to horseradish peroxidase applied to the central end of the sectioned pelvic nerve. The sub-populations of lumbosacral neurons innervating the corpus cavernosum of the penis or the dome of the bladder were identified using transsynaptic retrograde labeling by pseudorabies virus injected into these organs in different rats. In both wheat germ agglutinin-labeled and pseudorabies virus-labeled rats, serial coronal sections were cut through the spinal L5-S1 segments. Labeled neurons were revealed by histochemistry (peroxidase experiments) or immunohistochemistry (pseudorabies virus experiments). By means of a three-dimensional reconstruction software developed in our laboratory, three-dimensional models were calculated from each spinal section image series. They revealed the spatial organization of (i) preganglionic neurons and (ii) neurons innervating the bladder or the penis. The different three-dimensional models were subsequently merged into a single one which revealed the segregation, within the sacral parasympathetic nucleus, of the sub-populations of neurons. Neurons labeled by virus injected into the penis extended predominantly from the rostral part of the L6 segment to the rostral part of the S1 segment while those labeled by bladder injections were distributed predominantly from the caudal part of the L6 segment to the caudal part of the S1 segment. These results support the hypothesis of a viscerotopic organization of sacral neurons providing the spinal control of pelvic organs.

Immunohistochemical characterisation of pelvic autonomic ganglia in male mice

Pelvic ganglia are mixed sympathetic-parasympathetic ganglia and provide the majority of the autonomic innervation to the urogenital organs. Here we describe the structural and histochemical features of the major pelvic ganglion in the male mouse and compare two different mouse strains. The basic structural features of the ganglion are similar to those in the male rat. Almost all pelvic ganglion cells are monopolar and most are cholinergic. All contain either neuropeptide Y (NPY) or vasoactive intestinal peptide (VIP), or both peptides together. The peptide coexistence varies between strains, with C57BL/6 mice having similar proportions of neurons with NPY alone, VIP alone or both peptides. In contrast, virtually all pelvic neurons in the Quackenbush-Swiss (QS) strain express NPY, i.e. the level of VIP/NPY coexistence is much higher. Cholinergic axons provide the major nerve supply to epithelia of reproductive organs, bladder smooth muscle and, as described previously, penile erectile tissue. They also provide a minor component of the smooth muscle innervation of the prostate gland, seminal vesicles and vas deferens. Virtually all non-cholinergic pelvic ganglion cells are noradrenergic and contain NPY. Their major target is smooth muscle of reproductive organs. This study shows that the male mouse pelvic ganglion bears many similarities to that in the rat, but that VIP/NPY colocalisation is much more common in the mouse. We also show that there are differences in peptide expression in parasympathetic pelvic neurons between strains of mice. These studies provide the framework for future investigations on neural regulation of urogenital function, particularly in transgenic and knockout models.

Nicotinic mechanisms in the autonomic control of organ systems

Most visceral organs are under the control of the autonomic nervous system (ANS). Information on the state and function of these organs is constantly relayed to the central nervous system (CNS) by sensory afferent fibers. The CNS integrates the sensory inputs and sends neural commands back to the organ through the ANS. The autonomic ganglia are the final site for the integration of the message traveling from the CNS. Nicotinic acetylcholine receptors (nAChRs) are the main mediators of fast synaptic transmission in ganglia, and therefore, are key molecules for the processing of neural information in the ANS. This review focuses on the role of nAChRs in the control of organ systems such as heart, gut, and bladder. The autonomic control of these organ systems is discussed in the light of the results obtained from the analysis of mice carrying mutations targeted to nAChR subunits expressed in the ANS.

AMPA glutamatergic receptor-immunoreactive subunits are expressed in lumbosacral neurons of the spinal cord and neurons of the dorsal root and pelvic ganglia controlling pelvic functions in the rat

Sacral preganglionic neurons innervate the pelvic organs via a relay in the major pelvic ganglion. Pudendal motoneurons innervate striated muscles and sphincters of the lower urinary, genital and digestive tracts. The activity of these spinal neurons is regulated by sensory afferents of visceral and somatic origins. Glutamate is released by sensory afferents in the spinal cord, and interacts with a variety of receptor subtypes. The aim of the present study was to investigated the presence of AMPA glutamate receptor subunits (GluR1-GluR4) in the neural network controlling the lower urogenital and digestive tracts of male rats. We performed double-immunohistochemistry directed against a neuronal tracer, the cholera toxin beta subunit (Ctbeta) and each of the four receptor subunits. GluR1, GluR2 and GluR3 subunits were present in many sacral preganglionic neurons retrogradely labelled with Ctbeta applied to the pelvic nerve, and in some dorsolateral and dorsomedian motoneurons retrogradely labelled with Ctbeta injected in ischiocavernosus and bulbospongiosus muscles. The four subunits were detected in postganglionic neurons of the major pelvic ganglion retrogradely labelled with Ctbeta injected in the corpus cavernosum, and in some somata of sensory afferents of the L6 dorsal root ganglion labelled with Ctbeta applied to the dorsal penile nerve or injected in corpus cavernosum. The results provide a detailed knowledge of the neural targets expressing the various AMPA receptor subunits and suggest that part of the neural network that controls pelvic organs, including sensory afferents and postganglionic neurons, is sensitive to glutamate through the whole family of AMPA subunits.

Target specific organization and neuron types of the dog pelvic ganglia: a retrograde-tracing and immunohistochemical study

The major pelvic ganglion in both the rat and guinea pig has been extensively studied because of its anatomical simplicity. To clarify the target specific neural pathway in the diffusely distributed pelvic ganglia of larger animals, the pelvic plexus of the female dog was investigated by retrograde tracing and immunohistochemistry. The whole mount staining of the pelvic plexus with acetylcholinesterase histochemistry revealed 70-100 ganglia of varying sizes. Neurons retrogradely labeled from the rectum were mainly found in ganglia located in the dorso-caudal part of the plexus. The majority of these were non-catecholaminergic, immunoreactive for either calbindin (Calb) or neuropeptide Y (NPY), and characteristically associated with baskets of enkephalin (ENK)-immunoreactive varicose fibers. Neurons projecting to the utero-vaginal walls were distributed in ganglia located in the ventro-caudal part of the plexus. These mainly consisted of two major neuron groups: catecholaminergic Calb-immunoreactive neurons, and non-catecholaminergic neurons containing nitric oxide synthase (NOS) and/or vasoactive intestinal peptide (VIP), which were preferentially associated with a network of ENK-immunoreactive varicose fibers. Neurons retrogradely labeled from the urinary bladder mainly occurred in ganglia located around the junction between the ureter and the bladder. These consisted of catecholaminergic Calb neurons and noncatecholaminergic neurons containing Calb or NOS. Only a few ENK-immunoreactive fibers were found within the clusters of catecholaminergic neurons. These results indicate that organ specific neurons are located in separate ganglia and have both a distinctive composition of neuron types as well as different innervation by preganglionic fibers.

Neural crest stem cells undergo cell-intrinsic developmental changes in sensitivity to instructive differentiation signals

Rat neural crest stem cells (NCSCs) prospectively isolated from uncultured E14.5 sciatic nerve and transplanted into chick embryos generate fewer neurons than do NCSCs isolated from E10.5 neural tube explants. In addition, they differentiate primarily to cholinergic parasympathetic neurons, although in culture they can also generate noradrenergic sympathetic neurons. This in vivo behavior can be explained, at least in part, by a reduced sensitivity of sciatic nerve-derived NCSCs to the neurogenic signal BMP2 and by the observation that cholinergic neurons differentiate at a lower BMP2 concentration than do noradrenergic neurons in vitro. These results demonstrate that neural stem cells can undergo cell-intrinsic changes in their sensitivity to instructive signals, while maintaining multipotency and self-renewal capacity. They also suggest that the choice between sympathetic and parasympathetic fates may be determined by the local concentration of BMP2.

Modulation of the micturition reflex pathway by intravesical electrical stimulation: an experimental study in the rat

Intravesical electrical stimulation (IVES) is used clinically to improve bladder evacuation in patients with inadequate micturition contractions. The procedure involves field stimulation of Adelta bladder mechanoreceptor afferents resulting in a prolonged enhancement of the micturition reflex. The aim of the present experimental study in the rat was to identify the site for this neuromodulation, whether it was due to sensitization of bladder mechanoreceptors, to enhancement of transmission in the central micturition reflex pathway, or to improved effectiveness of the peripheral motor system of the bladder. The experiments were performed on female rats, anesthetized by alpha-chloralose. Multi-unit afferent or efferent activity was recorded from bladder pelvic nerve branches during repeated cystometries before and after IVES. The specific antagonist CPPene was used to block central glutaminergic receptors of NMDA type. Micturition threshold volume decreased significantly after IVES. The afferent threshold volume, peak response, and pressure sensitivity were unchanged as were the peak efferent activity and bladder contractility. There was no efferent activity until just before the micturition contraction. The IVES-induced decrease in micturition threshold was blocked by prior administration of the NMDA (N-methyl-D-aspartic acid) antagonist CPPene (3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid). The findings indicate that the IVES-induced modulation of the micturition reflex is due to an enhanced excitatory synaptic transmission in the central micturition reflex pathway. The observed modulation may account for the clinical beneficial effect of IVES treatment.

Nicotinic acetylcholine receptors in the autonomic control of bladder function

Micturition is achieved through complex neurological mechanisms involving somatic, autonomic and central components. This article briefly reviews recent findings on the autonomic control of urinary bladder function. Neuronal nicotinic acetylcholine receptors mediate fast synaptic transmission in autonomic ganglia, and activation of nicotinic receptors in parasympathetic bladder neurons produces contraction of the detrusor muscle. Autonomic ganglia contain transcripts for the alpha(3), alpha(4), alpha(5), alpha(7), beta(2) and beta(4) nicotinic subunits, which can assemble to form multiple nicotinic receptor subtypes, but the exact nicotinic receptor subunit composition in bladder ganglia is unknown. Mutant mice lacking the alpha(3) or the beta(2) and the beta(4) nicotinic subunits have enlarged bladders with dribbling urination and develop urinary infection and bladder stones. Bladder strips from alpha(3) null mice do not respond to nicotine but contract when stimulated with a muscarinic agonist or electric field stimulation. Mice lacking the beta(2) subunit have no overt bladder phenotype, and their bladders contract in response to nicotine. Surprisingly, bladder strips from beta(4) mutant mice do not respond to nicotine despite the absence of major bladder dysfunction in vivo. These findings suggest that nicotinic receptors containing the alpha(3) and the beta(4) subunits are necessary for normal bladder function.