A quantitative analysis of the afferent and extrinsic efferent innervation of specific regions of the bladder and urethra in the cat

Urothelial bladder afferents selectively project to L6/S1 levels and are more peptidergic than those projecting to the T13/L1 levels in female rats

This neuroanatomical study in four, adult, Sprague-Dawley female rats quantified the number of Urothelial (labeled by intravesical DiI dye administration) and Non-Urothelial (labeled by intraparenchymal injection of Fast blue dye) bladder primary afferent neurons (bPANs) located in the T13, L1, L6 and S1 dorsal root ganglia. Additional immunohistochemical labeling using antibodies to detect either Substance P or CGRP further characterized the bPAN samples as peptidergic or non-peptidergic. Cell counts indicated that Urothelial bPANs were more common at the L6/S1 levels and more likely to be identified as peptidergic when compared with bPANs characterized at T13/L1 levels and with Non-Urothelial bPANs. These studies provide additional evidence that at least two distinct neuronal populations, with differing localization of sensory terminals, differing peptide content, and differing projections to the central nervous system, are responsible for bladder sensation.

Safety and efficacy of intravesical instillation of resiniferatoxin in healthy cats: A preliminary study

Objectives

To evaluate the safety of intravesical application of resiniferatoxin (RTX) in healthy cats and its effects on calcitonin gene-related peptide (CGRP) and substance P (SP) produced by C-fibers.

Methods

Seven adult female cats received either 25 mL of saline (control; n = 1), or intravesical RTX at 5, 25, or 50 μg in 25 mL of saline to a final concentration of 0.2 μg/mL (318 nM), 1 μg/mL (1,591 nM), and 2 μg/mL (3,181 nM) (n = 2 per group). The treatment was instilled into the urinary bladder for 20 min. Plasma concentrations of RTX were measured at 0, 0.5, 1, and 4 h. Physical exam, complete blood count, and serum biochemical analysis were performed on day 0, 7, and 14. After 14 days, the sacral dorsal root ganglia (DRG) and the urinary bladder were harvested for histological and immunofluorescence analysis.

Results

Intravesical RTX was well tolerated and plasma concentrations were below the quantifiable limits except for one cat receiving 1 μg/mL. Mild to moderate histopathological changes, including epithelial changes, edema, and blood vessel proliferation, were observed at lower doses (0.2 and 1 μg/mL), and were more severe at the higher dose (2 μg/mL). C-fiber ablation was observed in the urinary bladder tissue at all doses, as shown by an apparent reduction of both CGRP and SP immunoreactive axons.

Conclusion

A dose of 25 μg (1 μg/mL) of RTX instilled in the urinary bladder of healthy cats appeared to decrease the density of SP and CGRP nerve axons innervating bladder and induced moderate changes in the bladder tissue.

The Influence of an Adrenergic Antagonist Guanethidine on the Distribution Pattern and Chemical Coding of Caudal Mesenteric Ganglion Perikarya and Their Axons Supplying the Porcine Bladder

This study was aimed at disclosing the influence of intravesically instilled guanethidine (GUA) on the distribution, relative frequency and chemical coding of both the urinary bladder intramural sympathetic nerve fibers and their parent cell bodies in the caudal mesenteric ganglion (CaMG) in juvenile female pigs. GUA instillation led to a profound decrease in the number of perivascular nerve terminals. Furthermore, the chemical profile of the perivascular innervation within the treated bladder also distinctly changed, as most of axons became somatostatin-immunoreactive (SOM-IR), while in the control animals they were found to be neuropeptide Y (NPY)-positive. Intravesical treatment with GUA led not only to a significant decrease in the number of bladder-projecting tyrosine hydroxylase (TH) CaMG somata (94.3 ± 1.8% vs. 73.3 ± 1.4%; control vs. GUA-treated pigs), but simultaneously resulted in the rearrangement of their co-transmitters repertoire, causing a distinct decrease in the number of TH⁺/NPY⁺ (89.6 ± 0.7% vs. 27.8 ± 0.9%) cell bodies and an increase in the number of SOM-(3.6 ± 0.4% vs. 68.7 ± 1.9%), calbindin-(CB; 2.06 ± 0.2% vs. 9.1 ± 1.2%) or galanin-containing (GAL; 1.6 ± 0.3% vs. 28.2 ± 1.3%) somata. The present study provides evidence that GUA significantly modifies the sympathetic innervation of the porcine urinary bladder wall, and thus may be considered a potential tool for studying the plasticity of this subdivision of the bladder innervation.

Bladder pressure encoding by sacral dorsal root ganglion fibres: implications for decoding

OBJECTIVE

We aim at characterising the encoding of bladder pressure (intravesical pressure) by a population of sensory fibres. This research is motivated by the possibility to restore bladder function in elderly patients or after spinal cord injury using implanted devices, so called bioelectronic medicines. For these devices, nerve-based estimation of intravesical pressure can enable a personalized and on-demand stimulation paradigm, which has promise of being more effective and efficient. In this context, a better understanding of the encoding strategies employed by the body might in the future be exploited by informed decoding algorithms that enable a precise and robust bladder-pressure estimation.

APPROACH

To this end, we apply information theory to microelectrode-array recordings from the cat sacral dorsal root ganglion while filling the bladder, conduct surrogate data studies to augment the data we have, and finally decode pressure in a simple informed approach.

MAIN RESULTS

We find an encoding scheme by different main bladder neuron types that we divide into three response types (slow tonic, phasic, and derivative fibres). We show that an encoding by different bladder neuron types, each represented by multiple cells, offers reliability through within-type redundancy and high information rates through semi-independence of different types. Our subsequent decoding study shows a more robust decoding from mean responses of homogeneous cell pools.

SIGNIFICANCE

We have here, for the first time, established a link between an information theoretic analysis of the encoding of intravesical pressure by a population of sensory neurons to an informed decoding paradigm. We show that even a simple adapted decoder can exploit the redundancy in the population to be more robust against cell loss. This work thus paves the way towards principled encoding studies in the periphery and towards a new generation of informed peripheral nerve decoders for bioelectronic medicines.

Real-Time Bladder Pressure Estimation for Closed-Loop Control in a Detrusor Overactivity Model

Overactive bladder (OAB) patients suffer from a frequent urge to urinate, which can lead to a poor quality of life. Current neurostimulation therapy uses open-loop electrical stimulation to alleviate symptoms. Continuous stimulation facilitates habituation of neural pathways and consumes battery power. Sensory feedback-based closed-loop stimulation may offer greater clinical benefit by driving bladder relaxation only when bladder contractions are detected, leading to increased bladder capacity. Effective delivery of such sensory feedback, particularly in real-time, is necessary to accomplish this goal. We implemented a Kalman filter-based model to estimate bladder pressure in real-time using unsorted neural recordings from sacral-level dorsal root ganglia, achieving a 0.88 ± 0.16 correlation coefficient fit across 35 normal and simulated OAB bladder fills in five experiments. We also demonstrated closed-loop neuromodulation using the estimated pressure to trigger pudendal nerve stimulation, which increased bladder capacity by 40% in two trials. An offline analysis indicated that unsorted neural signals had a similar stability over time as compared to sorted single units, which would require a higher computational load. We believe this paper demonstrates the utility of decoding bladder pressure from neural activity for closed-loop control; however, real-time validation during behavioral studies is necessary prior to clinical translation.

Changes in chemical coding of sympathetic chain ganglia (SChG) neurons supplying porcine urinary bladder after botulinum toxin (BTX) treatment

Botulinum toxin (BTX) is a neurotoxin used in medicine as an effective drug in experimental therapy of neurogenic urinary bladder disorders. We have investigated the influence of BTX on the chemical coding of sympathetic chain ganglia (SChG) neurons supplying the porcine urinary bladder. The toxin was injected into the wall of the bladder. SChG neurons were visualized by a retrograde tracing method with fluorescent tracer fast blue (FB) and their chemical coding was investigated by double-labelling immunohistochemistry with antibodies against dopamine β-hydroxylase (DβH; a marker of noradrenergic neurons), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), galanin (GAL), Leu(5)-enkephalin (L-ENK) and neuronal nitric oxide synthase (nNOS). In both the control (n = 5) and BTX-treated pigs (n = 5), the vast majority (91 ± 2.3 % and 89.8 ± 2.5 %, respectively) of FB-positive (FB+) nerve cells were DβH+. BTX injections caused a decrease in the number of FB+/DβH+ neurons that were immunopositive to NPY (39.5 ± 4.5 % vs 74.5 ± 11.9 %), VIP (8.9 ± 5.3 % vs 22.3 ± 8.8 %), SOM (5.8 ± 2.3 % vs 17.4 ± 3.7 %) or GAL (0.9 ± 1.2 % vs 5.4 ± 4.4 %) and a distinct increase in the number of FB+/DβH+ neurons that were immunoreactive to L-ENK (3.7 ± 2.9 % vs 1.1 % ± 0.8 %) or nNOS (7.7 ± 3.5 % vs 0.8 ± 0.6 %). Our study provides novel evidence that the therapeutic effects of BTX on the mammalian urinary bladder are partly mediated by SChG neurons.

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.

Immunohistochemical characteristics and distribution of sensory dorsal root Ganglia neurons supplying the urinary bladder in the male pig

The study determined the distribution and immunohistochemical coding of the sensory neurons innervating the male pig urinary bladder. Retrograde tracer Fast Blue was injected bilaterally into the bladder trigone, base or dome. The presence of neuropeptide Y (NPY), somatostatin (SOM), galanin (GAL), vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), calcitonin gene-related peptide (CGRP) and substance P (SP) were studied with immunofluorescence. Fast Blue-positive neurons were localized bilaterally in dorsal root ganglia from L1 to L6 and from S3 to S4 with specific differences regarding the injection site. The number of Fast Blue-positive neurons was higher in the right ganglia. Immunohistochemistry revealed that sensory neurons innervating the urinary bladder trigone, base and dome displayed immunoreactivities to CGRP, SP, NOS, GAL and SOM. Differences in the neuropeptide content were observed between the Fast Blue-positive neurons in lumbar and sacral ganglia. Taken together, these data indicate that the lumbar and sacral pathways probably play different roles in sensory transmission from the urinary bladder trigone, base and dome.

Localization of peripheral autonomic neurons innervating the boar urinary bladder trigone and neurochemical features of the sympathetic component

The urinary bladder trigone (UBT) is a limited area through which the majority of vessels and nerve fibers penetrate into the urinary bladder and where nerve fibers and intramural neurons are more concentrated. We localized the extramural post-ganglionic autonomic neurons supplying the porcine UBT by means of retrograde tracing (Fast Blue, FB). Moreover, we investigated the phenotype of sympathetic trunk ganglia (STG) and caudal mesenteric ganglia (CMG) neurons positive to FB (FB+) by coupling retrograde tracing and double-labeling immunofluorescence methods. A mean number of 1845.1±259.3 FB+ neurons were localized bilaterally in the L1-S3 STG, which appeared as small pericarya (465.6±82.7 µm²) mainly localized along an edge of the ganglion. A large number (4287.5±1450.6) of small (476.1±103.9 µm²) FB+ neurons were localized mainly along a border of both CMG. The largest number (4793.3±1990.8) of FB+ neurons was observed in the pelvic plexus (PP), where labeled neurons were often clustered within different microganglia and had smaller soma cross-sectional area (374.9±85.4 µm²). STG and CMG FB+ neurons were immunoreactive (IR) for tyrosine hydroxylase (TH) (66±10.1% and 52.7±8.2%, respectively), dopamine beta-hydroxylase (DβH) (62±6.2% and 52±6.2%, respectively), neuropeptide Y (NPY) (59±8.2% and 65.8±7.3%, respectively), calcitonin-gene-related peptide (CGRP) (24.1±3.3% and 22.1±3.3%, respectively), substance P (SP) (21.6±2.4% and 37.7±7.5%, respectively), vasoactive intestinal polypeptide (VIP) (18.9±2.3% and 35.4±4.4%, respectively), neuronal nitric oxide synthase (nNOS) (15.3±2% and 32.9±7.7%, respectively), vesicular acetylcholine transporter (VAChT) (15±2% and 34.7±4.5%, respectively), leuenkephalin (LENK) (14.3±7.1% and 25.9±8.9%, respectively), and somatostatin (SOM) (12.4±3% and 31.8±7.3%, respectively). UBT-projecting neurons were also surrounded by VAChT-, CGRP-, LENK-, and nNOSIR fibers. The possible role of these neurons and fibers in the neural pathways of the UBT is discussed.

Ion channel and receptor mechanisms of bladder afferent nerve sensitivity

Sensory nerves of the urinary bladder consist of small diameter A(delta) and C fibers running in the hypogastic and pelvic nerves. Neuroanatomical studies have revealed a complex neuronal network within the bladder wall. Electrophysiological recordings in vitro and in vivo have revealed several distinct classes of afferent fibers that may signal a wide range of bladder stimulations including physiological bladder filling, noxious distension, cold, chemical irritation and inflammation. The exact mechanisms that underline mechanosensory transduction in bladder afferent terminals remain ambiguous; however, a wide range of ion channels (e.g., TTX-resistant Na(+) channels, Kv channels and hyperpolarization-activated cyclic nucleotide-gated cation channels) and receptors (e.g., TRPV1, TRPM8, TRPA1, P2X(2/3), etc) have been identified at bladder afferent terminals and implicated in the generation and modulation of afferent signals. Experimental investigations have revealed that expression and/or function of these ion channels and receptors may be altered in animal models and patients with overactive and painful bladder disorders. Some of these ion channels and receptors may be potential therapeutic targets for bladder diseases.

Neural control of the urethra and development of pharmacotherapy for stress urinary incontinence

This review discusses the control of the urethra by the central nervous system, emphasizing the importance of nervous system control and the role of serotonin and noradrenaline in storage, micturition and sphincter reflexes. The concept of pharmacological neuromodulation and the use of pharmacological therapy as first-line therapy for stress urinary incontinence (SUI) is presented. Coordination between the urinary bladder and urethra is mediated by many reflex pathways organized in the brain and spinal cord. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes depend on interneuronal circuitry in the spinal cord and are modulated by descending pathways. It would therefore seem that neurotransmission in the central nervous system and periphery may be important in SUI, and moreover that pharmacological agents affecting these neurotransmitter pathways may be used to treat SUI. The central and peripheral mechanisms of action of duloxetine affect serotonin and noradrenaline neurotransmission in ways that may ameliorate the symptoms of SUI.

Supra and infralevator neurovascular pathways to the penile corpora cavernosa

The aim of this study was to provide a comprehensive description of both penile innervation and vascularisation. Eighty-five male cadavers were examined through gross and microscopic anatomical analysis. The pelvic nerve plexus had both parasympathetic and sympathetic roots. It was distributed to the external urethral sphincter giving rise to cavernous nerves which anastomosed in 70% of the cases with the pudendal nerve in the penile root. Accessory pudendal arteries were present in the pelvis in 70% of the cases, anastomosing in 70% of the cases with the cavernous arteries that originated from the pudendal arteries. Transalbugineal anastomoses were always seen between the cavernous artery and the spongiosal arterial network. There were 2 venous pathways, 1 in the pelvis and 1 in the perineum with a common origin from the deep dorsal penile vein. It is concluded that there are 2 neurovascular pathways destined for the penis that are topographically distinct. One is located in the pelvis and the other in the perineum. We were unable to determine the functional balance between these 2 anastomosing pathways but experimental data have shown that they are both involved in penile erection. These 2 neurovascular pathways, above and below the levator ani, together with their anastomoses, form a neurovascular loop around the levator ani.

Preganglionic fibers in the rat hypogastric nerve project bilaterally to pelvic ganglia

Stimulation of the hypogastric nerve (HGN) often evokes bilateral responses in some pelvic organs. Retrograde labeling studies indicate that axons of postganglionic neurons often cross to the opposite side. However, there is little information available as to whether preganglionic fibers in the HGN have a contralateral projection to pelvic ganglia. A retrograde tracer was injected into the left major pelvic ganglion (MPG) in rats receiving various lesions of preganglionic nerves (HGN and pelvic nerve, PN). The lumbar spinal cord was then examined for location and number of dye-filled neurons. In a second approach, the incidence of synaptophysin immunoreactivity (SN-IR) perineuronal profiles (baskets) was examined in the MPG and in the accessory pelvic ganglia (APG) after nerve lesions. Labeled neuronal profiles were found in spinal cord nuclei (Lumbar1-2) after dye injection of the MPG in animals with an intact contralateral HGN. Cutting both HGNs virtually eliminated dye labeling in the lumbar cord, as did severing commissural branches (CB) between pelvic ganglia (leaving the contralateral HGN intact). Some SN-IR baskets were found in the left APG when only the contralateral HGN was intact, but baskets were rare when all four preganglionic nerves were cut. It could not be determined whether the HGN projects to the contralateral MPG, since SN-IR baskets were numerous in the MPG even when all four nerves were cut. This study has shown that some preganglionic fibers in the HGN synapse on neurons in contralateral pelvic ganglia. Both the APG and MPG receive contralateral innervation, but it is likely that neurons in the APG are the primary target of this input. Thus, in addition to crossing postganglionic fibers, a portion of the bilateral control of pelvic tissues is accomplished by preganglionic fibers which target autonomic neurons in contralateral ganglia.

Sympathetic efferent pathways projecting to the bladder neck and proximal urethra in the rat

The sympathetic innervation of the rat bladder neck and proximal urethra (BN/PU) was investigated by measuring BN/PU pressure responses to electrical stimulation of a left lumbar splanchnic nerve (LSN) following consecutive transections of more distal nerves. L2-L6 LSN stimulation increased BN/PU pressure. BN/PU pressure responses did not change after section of the right hypogastric nerve (HGN) but significantly decreased after subsequent sectioning of the commissural branches (CB-MPG) between the right and left major pelvic ganglia (MPG) (22%) and the commissural branches (CB-APG) between right and left accessory pelvic ganglia (APG) (30%). In other animals BN/PU pressure responses were slightly decreased (< 11%) after sectioning the left HGN and then significantly decreased by subsequent sectioning of the CB-MPG (< 21%) and CB-APG (< 36%). BN/PU pressure responses were decreased by sectioning the branches from the MPG to the APG (25%) or postganglionic nerves (MPG-PN) from the MPG to the BN/PU (37%). When the HGN on one side and all branches from the MPG on the contralateral side except for the CB-MPG were transected, increases in BN/PU intraluminal pressure were still elicited by LSN stimulation but were eliminated by transection of the CB-MPG. These results indicate that the left lumbar sympathetic pathway to the BN/PU passes through multiple crossing points at the level of the inferior mesenteric ganglion, MPG and APG and that this pathway could maintain closure of the internal urethral sphincter following various unilateral neural injuries.

Pharmacological studies to examine the source of ATP released by pelvic nerve stimulation in the feline lower urinary tract

1. Pretreatment with 6-OHDA or bilateral sectioning of the hypogastric nerves decreased the noradrenaline content of lower urinary tract tissue. 2. Pelvic nerve stimulation-induced contractions were not significantly changed by either 6-OHDA pretreatment or bilateral sectioning of the hypogastric nerves. 3. Hypogastric nerve stimulation-induced contractions were significantly attenuated by the pretreatments. 4. Neither ATP- nor acetylcholine-induced contractions were significantly altered by either 6-OHDA or bilateral sectioning of the hypogastric nerves. 5. The data indicate that ATP, released by pelvic nerve stimulation, which induces a bladder contraction, is released from parasympathetic, cholinergic nerve fibres in the pelvic nerve trunks and not sympathetic, nor adrenergic nerve fibres also present in the pelvic nerve trunks.

Morphological and electrophysiological analysis of the peripheral and central afferent pathways from the clitoris of the cat

Afferent neurons projecting to the clitoris of the cat were identified by WGA-HRP tracing in the S1 and S2 dorsal root ganglia. An average of 433 cells were identified on each side of the animal. 85% and 15% of the labeled cells were located in the S1 and S2 dorsal root ganglia, respectively. The average cross sectional area of clitoral afferent neuron profiles was 1,479 +/- 627 micron2. Unilateral transection of the pudendal nerve reduced the number of labeled cells to 1% of that on the control side. Central projections of clitoral afferents were identified in the lumbo-sacral segments (L7-S3) of the spinal cord. HRP labeled fibers were located in the marginal zone on the medial side of dorsal horn and extended into the dorsal half of the dorsal gray commissure. Electrophysiological recordings detected axonal volleys in the pudendal nerve and S1 dorsal root in response to electrical stimulation (threshold, 1-4 V) of the clitoral surface. Estimated axonal conduction velocities at the two sites ranged from 7-27 m/s and 0.6-30 m/s, respectively. Multi-unit recordings from dorsal roots in the lumbo-sacral segments revealed that non-noxious pressure stimulation of the clitoris evoked discharges in the S1 dorsal root. Small increases were also detected in the S2 and L7 roots. Single unit discharges recorded from S1 dorsal roots were activated by electrical stimulation of the clitoral surface at thresholds of 0.6-1.2 V and latencies of 1.5-1.8 ms (estimated conduction velocities of 24-30 m/s.(ABSTRACT TRUNCATED AT 250 WORDS)

The pathophysiology of contractile activity in the chronic decentralized feline bladder

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

Afferent and sympathetic innervation of the dome and the base of the urinary bladder of the female rat

The afferent and sympathetic innervation of different regions of the urinary bladder (bladder dome vs. bladder base) was examined in the female rat using simultaneous injections of two fluorescent tracers. Retrogradely labeled cells were found in the dorsal root ganglia (DRG; L1-L3 and L6-S1), the sympathetic chain (SC; T12-L6), the inferior mesenteric ganglia (IMG) and the major pelvic ganglia (MPG). There were very few double-labeled cells, indicating that the dome and the base of the bladder receive innervation (afferent or sympathetic) from separate and distinct neuronal populations. Most of the sympathetic innervation of the bladder arose from the SC (dome: 77%; base: 89%) and it was carried equally by the hypogastric and pelvic nerves. The distributions of SC postganglionic neurons innervating the dome and the base of the bladder were very similar. In contrast, the contribution of IMG neurons was almost entirely restricted to the dome of the bladder (22%), with less than 1% innervating the base. Tyrosine hydroxylase-immunoreactive (TH) neurons in the MPG displayed a strong sexual dimorphism. Many TH neurons were found in the male MPG, but very few in the female MPG. In the female, these TH neurons projected almost exclusively to the bladder base of the female rat and were responsible for 10% of the sympathetic innervation of the base. Less than 1% innervated the dome. Therefore, prevertebral ganglia (IMG and MPG) show a strong regional selectivity in the innervation of the bladder of the female rat. The possible functional implications of this organization are discussed.

Evidence for the existence of a urethro-urethral excitatory reflex in urethane anesthetized rats: involvement of peripheral ganglionic structures

In urethane-anesthetized rats urethral distension with saline at the level of the external urethral sphincter elicited a series of slow phasic contractions with an amplitude between two and 18 mm. Hg. Contractions having an amplitude lower than four mm Hg were unaffected by i.v. or topical hexamethonium (HEX) or by topical tetrodotoxin (TTX). HEX or TTX transiently abolished or reduced the distension-evoked contractions having an amplitude between four and 18 mm. Hg. Administration of d-tubocurarine (d-Tc), atropine, bilateral section of pudendal nerves, spinalization (T12-S1) or bilateral removal of the major pelvic ganglia did not modify the distension-induced rhythmic urethral activity. In rats desensitized to capsaicin (four days before), both amplitude and frequency of urethral contractions did not differ from control value. In rats pretreated with atropine, administration of HEX still inhibited the distension-induced urethral contractions. Intravenous dimethylphenylpiperazinium (DMPP) triggered a rapid phasic contraction with an amplitude ranging between 15 and 25 mm. Hg. This effect was inhibited by previous administration of HEX. In accordance with histochemical studies showing spherical ganglionic cell bodies between the outermost striated muscle layer and the smooth muscular coat, present data indicate that distension of the external urethral sphincter reflexly activates urethral contractions, possibly through a local mechanism.

Urethral function after chronic cauda equina lesions in cats. I. The contribution of mechanical factors and sympathetic innervation to proximal sphincter dysfunction

We investigated the contribution of mechanical and sympathetic neural factors to proximal urethral sphincter dysfunction in the cat after chronic sacral rhizotomy. Concomitant vesicostomy prevented a decrease in the urethral pressure profile measured three months post-rhizotomy. Sympathetic influences on basal urethral perfusion pressure were the same in neurally-intact and chronic rhizotomised cats. A significant prazosin-sensitive component of basal urethral perfusion pressure remained after section of all extrinsic urethral innervation in both neurally-intact and chronic cats. Local intra-arterial 6-hydroxydopamine also abolished this component. After rhizotomy, noradrenaline content in the proximal urethra was significantly increased but there was no change in sensitivity to sympathetic stimulation. A small (5% of control) atropine-sensitive and prazosin-resistant constriction was seen only after chronic sacral rhizotomy. We conclude that a mechanical factor associated with bladder expression and not an alteration in sympathetic control is the major factor leading to diminished proximal urethral closure after vesicourethral lower motor neuron lesion. Furthermore, short adrenergic neurons have an important role in the maintenance of urethral pressure in the normal state and after lower motor neuron lesion.

Visceral pain: a review of experimental studies

This paper reviews clinical and basic science research reports and is directed toward an understanding of visceral pain, with emphasis on studies related to spinal processing. Four main types of visceral stimuli have been employed in experimental studies of visceral nociception: (1) electrical, (2) mechanical, (3) ischemic, and (4) chemical. Studies of visceral pain are discussed in relation to the use and 'adequacy' of these stimuli and the responses produced (e.g., behavioral, pseudoaffective, neuronal, etc.). We propose a definition of an adequate noxious visceral stimulus and speculate on spinal mechanisms of visceral pain.

Innervation of the spleen in the rat: evidence for absence of afferent innervation

Catecholaminergic fibers in the spleen have been well characterized in the rat and this innervation is believed to be an important source of modulation of the immune system. The presence or role of afferent feedback from the spleen has not been systematically investigated. We have examined whether the spleen receives afferent innervation from sensory ganglia and also have assessed the sources of efferent innervation to the spleen in the rat. The fluorescent retrograde anatomical tracers fluoro-gold (FGo) or fast blue (FB) were injected into the spleens of adult female rats and dorsal root, sympathetic chain, nodose, and celiac-mesenteric plexus ganglia were collected. In additional animals, the spleen was either injected with the anatomical tracer wheat germ agglutinin-horseradish peroxidase (WGA-HRP) or else regular HRP was applied to the cut end of the splenic nerve. Also, we examined the effects of cutting the splenic nerve on the retrograde labeling of cell bodies in the ganglia and on the catecholamine histochemistry of the spleen. The neuroanatomical results were based primarily upon the tracer FGo and verified that the celiac-mesenteric plexus ganglia provide a major efferent input to the spleen. Furthermore, lower thoracic sympathetic chain ganglia provide an additional and substantial efferent supply to the spleen. Cutting of the splenic nerve prevented retrograde labeling of cell bodies in the celiac-mesenteric plexus ganglia and sympathetic chain ganglia of rats injected with tracers into the spleen and also eliminated catecholamine histofluorescence in the spleen. In terms of afferent labeling, the results with FGo indicated that there were no cell bodies labeled in afferent ganglia following splenic injections.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent fibers in the reproductive system and pelvic viscera of female rats: anterograde tracing and immunocytochemical studies

Innervation of the female reproductive system provides an important signal for a variety of neuroendocrine reflexes and behaviors in the female rat. Although some studies suggest that afferent feedback from the gonads is involved in the hypothalamic control of gonadal function and pituitary hormone release, the extent and function of afferent feedback from the gonads in these neuroendocrine reflexes has yet to be clarified. Deafferentation studies have provided only partial support for the afferent control of the gonads. Some studies even suggest functional asymmetries in the neural control of the gonads, but knowledge regarding the neuroanatomical substrate for these possible neurogonadal interactions remains incomplete. Studies with retrograde tract tracers indicate that the ovaries receive a substantial afferent supply from lower thoracic-upper lumbar dorsal root ganglia. Despite stringent precautions to prevent diffusion of tracers following injections into the ovary or related nerves, many of the retrogradely labeled cell bodies identified by these studies may represent an overestimation of the extent of afferent innervation. We have reexamined the afferent innervation of the female reproductive tract by means of the anterograde transport of horseradish peroxidase (HRP) from thoracic, lumbar and sacral dorsal root ganglion to pelvic visceral organs and have studied the effects of unilateral ganglionectomy on substance P containing fibers in the ovary, oviduct and uterus. The neuroanatomical results show that the T13 and L1 dorsal root ganglia provide major afferent innervation to the cranial portion of the reproductive tract and the L6 and S1 dorsal root ganglia provide primary afferent fibers to the caudal portion of the reproductive tract as well as the bladder, rectum and perineum.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcitonin gene-related peptide immunoreactivity in afferent neurons supplying the urinary tract: combined retrograde tracing and immunohistochemistry

The innervation of rat and guinea pig urinary tract was examined using immunohistochemistry, radioimmunoassay and True Blue retrograde tracing techniques and was further assessed following both surgical and chemical denervation experiments. Substantial amounts of calcitonin gene-related peptide-like immunoreactivity (range 20-150 pmol/g) were detected in tissue extracts and localised to nerve fibres distributed throughout the urinary tract of both species, these being concentrated in the ureter and base of the bladder. In the guinea pig, the number and distribution pattern of calcitonin gene-related peptide-like immunoreactive nerves appeared to be identical to that of substance P-containing nerves, whereas in the rat the former predominated. Seven days after injection of the fluorescent dye True Blue into tissues of the urinary tract, retrogradely labelled cells were found in the dorsal root ganglia. These cells had a segmental distribution pattern which was specific for each of the injection sites. Thus, after injection of True Blue into the left kidney hilum a single group of labelled cells were found in the ipsilateral T10-L2 dorsal root ganglia. In contrast, injection into the left ureter produced labelled cells in two separate groups of ipsilateral ganglia (T11-L3 and L6-S1). Injection into the wall of the bladder and upper urethra resulted in bilateral labelling, with most labelled cells occurring in L6 and S1 ganglia. Approximately 90% of labelled cells in T10-L3 dorsal root ganglia displayed calcitonin gene-related peptide-like immunoreactivity, but only 60% of retrogradely labelled bladder neurons in L6-S1 ganglia were immunoreactive for this peptide. Adult guinea pigs and neonatal rats injected systemically with capsaicin subsequently exhibited a marked reduction both in the amount of calcitonin gene-related peptide immunostaining and the concentration of immunoreactive material in the urinary tract, dorsal root ganglia and spinal cord. In rats treated neonatally with capsaicin, there was a significant reduction in the number of retrogradely labelled cells and a hypertrophy of the bladder. Sectioning of the pelvic and hypogastric nerves in the rat also resulted in a depletion of calcitonin gene-related peptide-like immunoreactive nerves in the bladder, whereas chemical sympathectomy appeared to have no effect. The results indicate that calcitonin gene-related peptide immunoreactivity occurs in a major proportion of afferent neurons supplying the urinary tract of the rat and guinea pig.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional characterization of preganglionic neurons projecting in the lumbar splanchnic nerves: neurons regulating motility

Lumbar preganglionic neurons, which projected in the lumbar splanchnic nerves and were probably involved in regulating motility of colon and pelvic organs (motility-regulating, MR neurons), were analyzed for their discharge patterns. The responses of the neurons to the following stimuli were tested: stimulation of arterial baro- and chemoreceptors and of afferents from the urinary bladder, colon, mucosal skin of the anus and perianal hairy skin. The following findings were made: a total of 131 preganglionic neurons were classified as MR neurons; these reacted to natural stimulation of at least one of the afferent inputs from the urinary bladder, colon and anal and perianal skin. The ongoing activity of these neurons did not correlate with the cardiac cycle or the cycle of the artificial ventilation. Most of them did not respond to an increase of blood pressure produced by i.v. injection of adrenaline or noradrenaline; some showed a weak depression or weak excitation which, in the time course, was untypical for visceral vasoconstrictor neurons. Stimulation of arterial chemoreceptors either did not influence MR neurons or produced only a secondary response owing to contraction of the urinary bladder. Ninety-seven preganglionic MR neurons could be subclassified: MR1 neurons were excited by distension and contraction of the urinary bladder and/or inhibited by distension and contraction of the colon (n = 61), a few were excited from both organs (n = 4); MR2 neurons were inhibited by distension and contraction of the urinary bladder and/or excited by distension and contraction of the colon (n = 32). Ninety-five out of 121 MR neurons (78.5%) were excited, 10 (8%) were inhibited and 16 (13%) not influenced by mechanical shearing stimuli applied to the mucosal skin of the anus. Most neurons which were excited by anal stimulation were not influenced by mechanical stimulation of the perianal (perigenital) skin. Twenty-eight per cent of the MR neurons (18 out of 64) were excited or inhibited upon stimulation of perianal skin. A few of these (7 out of 64 neurons, 11%) were involved in reflex responses which were different from those elicited from anal skin. At present no further consistent subclassification of MR1 and MR2 neurons appears possible on the basis of the excitatory and inhibitory anal and perianal reflexes. The results show that the population of visceral preganglionic neurons, which are probably involved in regulation of motility of colon and pelvic organs, is not homogeneous and probably consists of several subpopulations.

Bladder and urethral function and supersensitivity to subcutaneously administered bethanechol in cats with chronic cauda equina lesions

The failure of bethanechol chloride to induce voiding in patients with neurogenic bladder, despite a positive bethanechol test, is being reported more frequently. An experimental model was designed in the cat to study the response of the bladder and urethra to subcutaneous and intraarterial bethanechol after complete and partial sacral decentralization. Complete sacral rhizotomy abolished the micturition reflex. Basal urethral perfusion pressure was not affected by complete sacral rhizotomy and a significant part of this basal urethral pressure remained sympathetically mediated. However, the urethral constriction response to bladder filling was lost in half the cats with complete lesions. Bladder and urethral supersensitivity to bethanechol chloride in cats with complete lesions was characterized by a shift to the left of the i.a. dose-response curve, and by the presence of responses to doses of s.c. bethanechol chloride which are subthreshold in normal cats. The urethra also showed exaggerated constriction responses to i.a. and s.c. bethanechol. After complete lesions a part of the bladder and urethral responses to s.c. bethanechol was adrenergically mediated and exerted through the vesicourethral short neuron system. The rest of the response was due to stimulation of urethral muscarinic receptors. Partial sacral lesions were compatible with a micturition reflex and the urethra retained its reflex response to bladder distension. After partial decentralization the bladder and urethra also showed responses to subthreshold doses of s.c. bethanechol. While the bladder response to s.c. bethanechol did not show a significant adrenergic component in cats with partial lesions, most of the urethral response was sympathetically mediated. In conclusion, complete cauda equina lesions result in an areflexic detrusor with frequent loss of the urethral responsiveness to bladder filling. Urethral supersensitivity to s.c. bethanechol might be responsible for a non-voiding outcome after bethanechol injection in patients with complete cauda equina lesions, despite a positive bethanechol test. Because the detrusor reflex is preserved and the urethra is less supersensitive to bethanechol after partial cauda equina lesions, these may represent a better indication for bethanechol therapy than do complete ones.

Axonal branching of canine sympathetic postganglionic cardiopulmonary neurons. A retrograde fluorescent labeling study

In 11 dogs fluorescent retrograde tracers were injected into physiologically identified left-sided sympathetic cardiopulmonary nerves. When two different ipsilateral cardiopulmonary nerves were injected, labeled cells from each injected nerve had overlapping distributions in the middle cervical and stellate ganglia. Most retrogradely labeled neurons were located in the middle cervical ganglion and cranial pole of the stellate ganglion. Following the injection of two different tracers into two different nerves, some neurons in the middle cervical ganglion were retrogradely labeled with two tracers. Double-labeled neurons were rarely found in the stellate ganglion. There were areas within the ganglia in which labeled neurons projected predominantly to one cardiopulmonary nerve. In the thoracic autonomic nervous system Fast Blue was transported most effectively. Bisbenzimide was not transported as well as Fast Blue and Nuclear Yellow was very poorly transported in cardiopulmonary nerves. The results demonstrate that some efferent postganglionic sympathetic neurons project axons into at least two different cardiopulmonary nerves and that an anatomical substrate for axo-axonal reflexes exists in the thoracic sympathetic nervous system.