Hypertrophy and reversal of hypertrophy in rat pelvic ganglion neurons

Spinal cord injury leads to atrophy in pelvic ganglia neurons

Among the most devastating sequelae of spinal cord injury (SCI) are genitourinary and gastrointestinal dysfunctions. Post-ganglionic neurons in pelvic ganglia (PG) directly innervate and regulate the function of the lower urinary tract (LUT), bowel, and sexual organs. A better understanding of how SCI affects PG neurons is essential to develop therapeutic strategies for devastating gastrointestinal and genitourinary complications ensuing after injury. To evaluate the impact of SCI on the morphology of PG neurons, we used a well- characterized rat model of upper thoracic SCI (T3 transection) that causes severe autonomic dysfunction. Using immunohistochemistry for neuronal markers, the neuronal profile size frequency distribution was quantified at one-, four-, and eight-weeks post SCI using recursive translation. Our investigation revealed an SCI-dependent leftward shift in neuronal size (i.e. atrophy), observable as early as one-week post injury. However, this effect was more pronounced at four and eight-weeks post-SCI. These findings demonstrate the first characterization of SCI-associated temporal changes in morphology of PG neurons and warrant further investigation to facilitate development of therapeutic strategies for recovery of autonomic functions following SCI.

Neurite outgrowth in cultured mouse pelvic ganglia - Effects of neurotrophins and bladder tissue

Neurotrophic factors regulate survival and growth of neurons. The urinary bladder is innervated via both sympathetic and parasympathetic neurons located in the major pelvic ganglion. The aim of the present study was to characterize the effects of the neurotrophins nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) on the sprouting rate of sympathetic and parasympathetic neurites from the female mouse ganglion. The pelvic ganglion was dissected out and attached to a petri dish and cultured in vitro. All three factors (BDNF, NT-3 and NGF) stimulated neurite outgrowth of both sympathetic and parasympathetic neurites although BDNF and NT-3 had a higher stimulatory effect on parasympathetic ganglion cells. The neurotrophin receptors TrkA, TrkB and TrkC were all expressed in neurons of the ganglia. Co-culture of ganglia with urinary bladder tissue, but not diaphragm tissue, increased the sprouting rate of neurites. Active forms of BDNF and NT-3 were detected in urinary bladder tissue using western blotting whereas tissue from the diaphragm expressed NGF. Neurite outgrowth from the pelvic ganglion was inhibited by a TrkB receptor antagonist. We therefore suggest that the urinary bladder releases trophic factors, including BDNF and NT-3, which regulate neurite outgrowth via activation of neuronal Trk-receptors. These findings could influence future strategies for developing pharmaceuticals to improve re-innervation due to bladder pathologies.

Caudal mesenteric ganglion in the sheep - macroanatomical and immunohistochemical study

The caudal mesenteric ganglion (CaMG) is a prevetrebral ganglion which provides innervation to a number of organs in the abdominal and pelvic cavity. The morphology of CaMG and the chemical coding of neurones in this ganglion have been described in humans and many animal species, but data on this topic in the sheep are entirely lacking. This prompted us to undertake a study to determine the localization and morphology of sheep CaMG as well as immunohistochemical properties of its neurons. The study was carried out on 8 adult sheep, weighing from 40 to 60 kg each. The sheep were deeply anaesthetised and transcardially perfused with 4% paraformaldehyde. CaMG-s were exposed and their location was determined. Macroanatomical observations have revealed that the ovine CaMG is located at the level of last two lumbar (L5 or L6) and the first sacral (S1) vertebrae. The ganglion represents an unpaired structure composed of several, sequentially arranged aggregates of neurons. Immunohistochemical investigations revealed that nearly all (99.5%) the neurons were DβH-IR and were richly supplied by VACHT-IR nerve terminals forming "basket-like" structures around the perikarya. VACHT-IR neurones were not determined. Many neurons (55%) contained immunoreactivity to NPY, some of them (10%) stained for Met-ENK and solitary nerve cells were GAL-positive. CGRP-IR nerve fibres were numerous and a large number of them simultaneously expressed immunoreactivity to SP. Single, weakly stained neurones were SP-IR and only very few nerve cells weakly stained for VIP.

Bladder outlet obstruction causes up-regulation of nicotinic acetylcholine receptors in bladder-projecting pelvic ganglion neurons

Pelvic ganglion (PG) neurons relay sympathetic and parasympathetic signals to the lower urinary tract, comprising the urinary bladder and bladder outlet, and are thus essential for both storage and voiding reflexes. Autonomic transmission is mediated by activation of the nicotinic acetylcholine receptor (nAChR) in PG neurons. Previously, bladder outlet obstruction (BOO), secondary to benign prostatic hyperplasia, was found to increase soma sizes of bladder-projecting PG neurons. To date, however, it remains unknown whether these morphological changes are accompanied by functional plasticity in PG neurons. In the present study, we investigated whether BOO alters acetylcholine receptor (nAChR) transcript expression and current density in bladder PG neurons. Partial ligation of the rat urethra for six weeks induced detrusor overactivity (DO), as observed during cystometrical measurement. In rats exhibiting DO, membrane capacitance of parasympathetic bladder PG neurons was selectively increased. Real-time PCR analysis revealed that BOO enhanced the expression of the transcripts encoding the nAChR α3 and β4 subunits in PG neurons. Notably, BOO significantly increased ACh-evoked current density in parasympathetic bladder PG neurons, whereas no changes were observed in sympathetic bladder and parasympathetic penile PG neurons. In addition, other ligand-gated ionic currents were immune to BOO in bladder PG neurons. Taken together, these data suggest that BOO causes upregulation of nAChR in parasympathetic bladder PG neurons, which in turn may potentiate ganglionic transmission and contribute to the development of DO.

The role of brain-derived neurotrophic factor (BDNF) in the development of neurogenic detrusor overactivity (NDO)

Neurogenic detrusor overactivity (NDO) is a well known consequence of spinal cord injury (SCI), recognizable after spinal shock, during which the bladder is areflexic. NDO emergence and maintenance depend on profound plastic changes of the spinal neuronal pathways regulating bladder function. It is well known that neurotrophins (NTs) are major regulators of such changes. NGF is the best-studied NT in the bladder and its role in NDO has already been established. Another very abundant neurotrophin is BDNF. Despite being shown that, acting at the spinal cord level, BDNF is a key mediator of bladder dysfunction and pain during cystitis, it is presently unclear if it is also important for NDO. This study aimed to clarify this issue. Results obtained pinpoint BDNF as an important regulator of NDO appearance and maintenance. Spinal BDNF expression increased in a time-dependent manner together with NDO emergence. In chronic SCI rats, BDNF sequestration improved bladder function, indicating that, at later stages, BDNF contributes NDO maintenance. During spinal shock, BDNF sequestration resulted in early development of bladder hyperactivity, accompanied by increased axonal growth of calcitonin gene-related peptide-labeled fibers in the dorsal horn. Chronic BDNF administration inhibited the emergence of NDO, together with reduction of axonal growth, suggesting that BDNF may have a crucial role in bladder function after SCI via inhibition of neuronal sprouting. These findings highlight the role of BDNF in NDO and may provide a significant contribution to create more efficient therapies to manage SCI patients.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

Neurotrophins in the lower urinary tract: becoming of age

The lower urinary tract (LUT) comprises a storage unit, the urinary bladder, and an outlet, the urethra. The coordination between the two structures is tightly controlled by the nervous system and, therefore, LUT function is highly susceptible to injuries to the neuronal pathways involved in micturition control. These injuries may include lesions to the spinal cord or to nerve fibres and result in micturition dysfunction. A common trait of micturition pathologies, irrespective of its origin, is an upregulation in synthesis and secretion of neurotrophins, most notably Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF). These neurotrophins are produced by neuronal and non-neuronal cells and exert their effects upon binding to their high-affinity receptors abundantly expressed in the neuronal circuits regulating LUT function. In addition, NGF and BDNF are present in detectable amounts in the urine of patients suffering from various LUT pathologies, suggesting that analysis of urinary NGF and BDNF may serve as likely biomarkers to be studied in tandem with other factors when diagnosing patients. Studies with experimental models of bladder dysfunction using antagonists of NGF and BDNF receptors as well as scavenging agents suggest that those NTs may be key elements in the pathophysiology of bladder dysfunctions. In addition, available data indicates that NGF and BDNF might constitute future targets for designing new drugs for better treatment of bladder dysfunction.

Morphological and quantitative study of the myenteric plexus in the human tenia coli

The longitudinal muscle in the large intestine in humans and some other mammalian species is concentrated in regions known as "tenia coli." The myenteric plexus under the tenia is believed to be highly developed to control the adjacent large muscle mass, however, data on the innervation of this region are very scarce. We used whole mount preparations of human colon to characterize the organization of the myenteric plexus under the tenia coli (UT) and compared it with the plexus between the tenia (BT). Using histochemical staining for NADPH diaphorase, we found that the meshwork UT was 50% denser than BT, and that the ganglia UT were 30% wider. The density and size of the NADPH-d positive neurons UT were similar to those of BT. We conclude that the myenteric plexus UT is considerably more developed than BT, and suggest to understand the control of colonic motility, the myenteric plexus UT needs to be further investigated.

Paracrine control of vascular innervation in health and disease

Proper vascular regulation is of paramount importance for the control of blood flow to tissues. In particular, the regulation of peripheral resistance arteries is essential for several physiological processes, including control of blood pressure, thermoregulation and increase of blood flow to central nervous system and heart under stress conditions such as hypoxia. Arterial tone is regulated by the periarterial autonomic nervous plexus, as well as by endothelium-dependent, myogenic and humoral mechanisms. Underscoring the importance of proper vascular regulation, defects in these processes can lead to diseases such as hypertension, orthostatic hypotension, Raynaud's phenomenon, defective thermoregulation, hand-foot syndrome, migraine and congestive heart failure. Here, we review the molecular mechanisms controlling the development of the periarterial nerve plexus, retrograde and localized signalling at neuro-effector junctions, the molecular and cellular mechanisms of vascular regulation and adult plasticity and maintenance of periarterial innervation. We particularly highlight a newly discovered role for vascular endothelial growth factor in the structural and functional maintenance of arterial neuro-effector junctions. Finally, we discuss how defects in neuronal vascular regulation can lead to disease.

Hypertrophy and neuron loss: structural changes in sheep SCG induced by unilateral sympathectomy

Recently, superior cervical ganglionectomy has been performed to investigate a variety of scientific topics from regulation of intraocular pressure to suppression of lingual tumour growth. Despite these recent advances in our understanding of the functional mechanisms underlying superior cervical ganglion (SCG) growth and development after surgical ablation, there still exists a need for information concerning the quantitative nature of the relationships between the removed SCG and its remaining contralateral ganglion and between the remaining SCG and its modified innervation territory. To this end, using design-based stereological methods, we have investigated the structural changes induced by unilateral ganglionectomy in sheep at three distinct timepoints (2, 7 and 12 weeks) after surgery. The effects of time, and lateral (left-right) differences, were examined by two-way analyses of variance and paired t-tests. Following removal of the left SCG, the main findings were: (i) the remaining right SCG was bigger at shorter survival times, i.e. 74% at 2 weeks, 55% at 7 weeks and no increase by 12 weeks, (ii) by 7 weeks after surgery, the right SCG contained fewer neurons (no decrease at 2 weeks, 6% fewer by 7 weeks and 17% fewer by 12 weeks) and (iii) by 7 weeks, right SCG neurons were also larger and the magnitude of this increase grew substantially with time (no rise at 2 weeks, 77% by 7 weeks and 215% by 12 weeks). Interaction effects between time and ganglionectomy-induced changes were significant for SCG volume and mean perikaryal volume. These findings show that unilateral superior cervical ganglionectomy has profound effects on the contralateral ganglion. For future investigations, it would be interesting to examine the interaction between SCGs and their innervation targets after ganglionectomy. Is the ganglionectomy-induced imbalance between the sizes of innervation territories the milieu in which morphoquantitative changes, particularly changes in perikaryal volume and neuron number, occur? Mechanistically, how would those changes arise? Are there any grounds for believing in a ganglionectomy-triggered SCG cross-innervation and neuroplasticity?

Partial urethral obstruction: ATF3 and p-c-Jun are involved in the growth of the detrusor muscle and its motor innervation

OBJECTIVE

Infravesical obstruction leads to growth of urinary bladder smooth-muscle cells. The ganglion cells innervating the bladder muscle also increase in size. Stretch of detrusor muscle cells rapidly activates c-Jun NH₂-terminal kinase (JNK), which phosphorylates the transcription factor c-Jun, and stimulates the synthesis of the cotranscription factor ATF3. The aim of the study was to determine whether ATF3 and p-c-Jun were involved in growth of bladder smooth-muscle and ganglion cells.

MATERIAL AND METHODS

The urethra was partially obstructed in female rats. After 3 days or 10 weeks bladders were weighed, fixated and cut for immunohistochemistry to demonstrate ATF3 and p-c-Jun. Ganglia were processed separately. Unoperated and sham-operated rats were used as controls.

RESULTS

There was no ATF3 or p-c-Jun in control detrusor muscle. After 3 days of obstruction bladder weight had nearly doubled. Almost all nuclei in the detrusor showed immunofluorescence for ATF3 and p-c-Jun. After 10 weeks bladder weight had increased 10-fold. Almost all detrusor nuclei still showed p-c-Jun, but few had ATF3 activity. In control ganglia there was no ATF3 and only faint nuclear p-c-Jun activity. After 3 days of obstruction the ganglion cells had increased in size and many nuclei showed intense immunofluorescence for ATF3 and p-c-Jun. After 10 weeks the ganglion cell size had increased further. There was no ATF3 activity and no more p-c-Jun than in control ganglia.

CONCLUSION

ATF3 and p-c-Jun seem to be involved in the growth of the detrusor muscle and its motor innervation following infravesical outlet obstruction.

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

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

Nerve distribution in rat urinary bladder after incorporation of acellular matrix graft or subtotal cystectomy

OBJECTIVE

In the treatment of reduced bladder capacity, matrix grafts have been used as a scaffold into which cell elements from the native bladder grow, eventually forming a new bladder segment. Functioning motor nerve endings in such segments in the rat have been demonstrated, although little is known about nerve distribution. We compare the pattern of nerve distribution in scaffold-augmented rat bladders with that in bladders regrown after subtotal cystectomy and that in control bladders.

MATERIAL AND METHODS

Female Sprague-Dawley rats were either subtotally cystectomized (n=7) or had a part of the bladder dome replaced by an acellular collagen (small intestinal submucosa) matrix graft (n=10). Fourteen age-matched, unoperated animals were used as controls. Two and a half to 10 months after surgery the bladders were stained for acetylcholinesterase and studied in wholemounts.

RESULTS

No ganglion neurons were observed in any of the bladders. On their ventral side the control bladders showed longitudinal nerve trunks, running in parallel along the longitudinally oriented muscle bundles, while on the lateral and dorsal aspects the nerves were thinner, more irregularly arranged and frequently branched. In the bladders regrown after subtotal cystectomy, the ventral nerves were seen running obliquely to the still longitudinally oriented muscle bundles, resembling the pattern of the normal bladder base; the pattern of the dorsolateral nerves was the same as that in the controls. In the matrix bladders, the muscle and nerve patterns in the native part were the same as those in controls. Muscle bundles were growing into the matrix, accompanied by nerves, which showed limited branching when entering the matrix, usually running in parallel to the muscle, but then branching within the matrix.

CONCLUSIONS

The nerves in the matrix grafts and the regrown parts of the subtotally cystectomized bladders derive from preexisting nerves in the bladder. In neither case does the nerve trunk or muscle bundle arrangement fully attain the pattern found in normal bladders.

Amikacin: A Novel Modulator of Vesical and Prostate Efferences. An in vitro Experimental Study

The autonomic efferent neurotransmission to the bladder and prostate smooth muscle is a potential target for drug therapy of specific low urinary tract disfunction (LUTD). Since amikacin and other amynoglicosides were reported to affect neurotransmission by a pre-junctional mechanism, we investigated the effect of amikacin on isolated rat and human detrusor smooth muscle contraction and on isolated rat and human prostate contraction, to further evaluate its potential relaxant properties.

Materials and Methods

Samples of detrusor smooth muscle and prostate tissue, obtained from 97 rats and 16 patients undergoing surgery, were studied through the measurement of isometric contraction induced by electrical field stimulation (EFS) and other pharmacological stimuli in the presence or absence of 1mM amikacin in a low-Ca medium.

Results

Amikacin 1 mM significantly reduced contraction of isolated rat and human detrusor muscle and prostate, achieved with pre-junctional stimulation, while no significant effect was observed on contraction induced by pharmacological post-junctional stimulators. EFS contraction inhibited by amikacin was restored after addition of calcium chloride. The amikacin effect was comparable to the effect of magnesium ions, which are known to exert a pre-junctional inhibition of neurotransmitter release.

Conclusions

Amikacin significantly inhibited rat and human detrusor and prostate contraction evoked by pre-junctional stimulation in vitro, suggesting a depressant effect on autonomic efferent neurotransmission. Further pharmacokinetics studies and researches on related compounds may hold potential for future development in the treatment of specific low urinary tract disfunction (LUTD).

Plasticity of rat small intestine after removal of a chronic mechanical obstruction

Chronic intestinal obstruction is associated with morphological changes and functional disorders clinically reported and experimentally documented in laboratory animals. In contrast, little is known about the properties of the hypertrophied intestine after removal of the obstruction. In the present study, we removed the ileal obstruction previously applied to the ileum of rats and, after 1 or 2 weeks, studied in vitro the motor responses of de-obstructed segments of intestine to pharmacological or electrical field stimulation (EFS). By 2 weeks after de-obstruction, maximal contractile responses to receptor (acetylcholine) and non-receptor (K(+)) mediated stimuli were comparable in operated and control tissues; furthermore, the loss of sensitivity to nitric oxide (NO) unmasked in obstructed tissues was, after de-obstruction, replaced by supersensitivity to exogenous NO and vasoactive intestinal polypeptide, probably acting through cyclic nucleotide-independent pathways. Despite the complete recovery of smooth muscle responses, neurogenic contractions remained impaired in de-obstructed tissue; however, the equal contribution of cholinergic/peptidergic components to EFS responses could represent a sign of gradual but delayed recovery of enteric neurotransmission.

Mechanisms of Disease: the role of nerve growth factor in the pathophysiology of bladder disorders

The case is compelling for the involvement of nerve growth factor (NGF) in the pathogenesis of lower urinary tract disease, especially in conditions with altered neural function. Remodeling of the micturition pathways occurs following experimental bladder-outlet obstruction, denervation, spinal cord injury, cystitis, and diabetes mellitus. Clinically, NGF levels are elevated in the bladders of men with benign prostatic hyperplasia, women with interstitial cystitis and in patients with idiopathic overactive bladder. Blockade of NGF, using either an endogenous antibody or an antibody against the NGF receptor, prevents neural plasticity and bladder overactivity in experimental models of these conditions. The ability of NGF to trigger bladder overactivity might rely on altering the properties of sodium or potassium channels (or their expression) in bladder afferent fibers. Therapies based on altered NGF levels, or changes in channel properties in afferent nerves, represent an intriguing avenue of investigation for the management of detrusor overactivity or diabetic cystopathy.

Morphological and electrophysiological changes in mouse dorsal root ganglia after partial colonic obstruction

There is evidence that sensitization of neurons in dorsal root ganglia (DRG) may contribute to pain induced by intestinal injury. We hypothesized that obstruction-induced pain is related to changes in DRG neurons and satellite glial cells (SGCs). In this study, partial colonic obstruction was induced by ligation. The neurons projecting to the colon were traced by an injection of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate into the colon wall. The electrophysiological properties of DRG neurons were determined using intracellular electrodes. Dye coupling was examined with an intracellular injection of Lucifer yellow (LY). Morphological changes in the colon and DRG were examined. Pain was assessed with von Frey hairs. Partial colonic obstruction caused the following changes. First, coupling between SGCs enveloping different neurons increased 18-fold when LY was injected into SGCs near neurons projecting to the colon. Second, neurons were not coupled to other neurons or SGCs. Third, the firing threshold of neurons projecting to the colon decreased by more than 40% (P < 0.01), and the resting potential was more positive by 4-6 mV (P < 0.05). Finally, the number of neurons displaying spontaneous spikes increased eightfold, and the number of neurons with subthreshold voltage oscillations increased over threefold. These changes are consistent with augmented neuronal excitability. The pain threshold to abdominal stimulation decreased by 70.2%. Inflammatory responses were found in the colon wall. We conclude that obstruction increased neuronal excitability, which is likely to be a major factor in the pain behavior observed. The augmented dye coupling between glial cells may contribute to the neuronal hyperexcitability.

Effect of spinal cord injury on urinary bladder spinal neural pathway: a retrograde transneuronal tracing study with pseudorabies virus

OBJECTIVES

To determinate the effect of acute and chronic spinal cord injury (SCI) resulting from thoracic cord transection on the urinary bladder spinal neural pathway.

METHODS

Seventy-six adult Sprague-Dawley rats were randomly divided into four groups, non-SCI (normal rats undergoing no surgical procedure except pseudorabies virus [PRV] injection), SCI(b) (SCI and PRV injected immediately after SCI), SCI(c) (SCI and PRV injected at 3 weeks after SCI), and SCI(d) (SCI and PRV injected at 3 months after SCI). Transcardiac perfusion fixation was done at appropriate survival periods after PRV injection into the bladder wall tissue. Sections of the dorsal root ganglion, spinal cord, and brain were processed for visualization of the virus by the streptavidin-peroxidase immunohistochemical procedure.

RESULTS

The bladder weight of the non-SCI, SCI(b), SCI(c), SCI(d) rats was 144 +/- 9 mg, 142 +/- 8 mg, 486 +/- 51 mg, and 656 +/- 69 mg, respectively. The time-ordered flow charts of PRV tracing were similar in the non-SCI and SCI rats. The cross-sectional area of the labeled dorsal root ganglion cell profiles increased significantly after SCI (P <0.001): 593 +/- 40 microm2, 588 +/- 39 microm2, 815 +/- 53 microm2, and 902 +/- 57 microm2 in the non-SCI, SCI(b), SCI(c), SCI(d) rats, respectively. The number of labeled cells in the dorsal horn in the L6 and S1 segments 3 days after PRV injection markedly increased in chronic SCI rats, as did the number of labeled motor neurons 4 days after injection.

CONCLUSIONS

Acute and chronic SCI have no effect on the process of virus transneuronal transport below the level of the lesion. Subsequent to chronic SCI, reorganization of the micturition reflex pathways may occur.

Macro- and microstructural organization of the rabbit's celiac-mesenteric ganglion complex (Oryctolagus cuniculus)

The macro- and microstructures of the rabbit celiac-mesenteric ganglion complex are described in 20 young animals. We found ten celiac ganglia, twenty-seven cranial mesenteric ganglia and eleven celiac-mesenteric ganglia. The celiac ganglia had a rectangular shape in nine cases (90%) and a circular one in one case (10%). The cranial mesenteric ganglia presented triangular (66.7%), rectangular (11.1%), L-shape (18.5%) and semi-lunar (3.7%) arrangements. The celiac-mesenteric ganglia were organized in three patterns: a single left celiac-mesenteric ganglion having a caudal portion (72.7%); celiac-mesenteric ganglia without a caudal portion (18.2%) and a single celiac-mesenteric ganglion with two portions: left and right (9.1%). The microstructure was investigated in nine celiac-mesenteric ganglia. The results showed that the celiac-mesenteric ganglion is actually a ganglion complex constituted of an agglomerate of ganglionic units separated by nerve fibers, capillaries and septa of connective tissue. Using the semi-thin section method we described the cellular organization of the celiac-mesenteric ganglion complex. Inside of each ganglionic unit, there were various cell types: principal ganglion neurons (PGN), glial cells (satellite cells) and SIF cells (small intensely fluorescent cells or small granular cells), which are the cytologic basis for each ganglionic unit of the rabbit's celiac-mesenteric ganglion complex.

Macro and microstructural organization of the dog's caudal mesenteric ganglion complex (Canis familiaris-Linnaeus, 1758)

The caudal mesenteric ganglion (CMG) is located ventral to the abdominal aorta involving the initial portion of the caudal mesenteric artery. Its macro and microstructural organization was studied in 40 domestic dogs. From the CMG, there were three nerves: the main hypogastric, the left hypogastric and the right hypogastric. The main hypogastric nerve emits two branches: the left colonic nerve and the cranial rectal nerve. Afterwards they give rise to branches to the descending colon (colonic nerves) and rectum (rectal nerves). The cranial rectal nerve, and left and right hypogastric nerves were directed to the pelvic ganglia. The microscopic study permitted the observation of the histological organization of the CMG, which is a ganglionic complex composed of an agglomeration of ganglionic units. Each ganglionic unit is composed of three major cell types: principal ganglion neurones (PGNs), glial cells and small intensely fluorescent (SIF) cells, and they were separated by nerve fibres, septa of connective tissue (types 1 and 3 collagen fibres), fibroblasts and intraganglionic capillaries. Hence, the ganglionic unit is the morphological support for the microstructural organization of the CMG complex. Further, each ganglionic unit is constituted by a cellular triad (SIF cells, PGN and glial cells), which is the cytological basis for each ganglionic unit.

Regeneration of myenteric plexus in the mouse colon after experimental denervation with benzalkonium chloride

Recent reports suggest a far greater plasticity in nerve tissue than previously believed. As the digestive tract is exposed to a variety of insults, this question is relevant to enteric nerves, but little is known about their ability to recover from damage. To address this problem, we ablated the myenteric plexus of the mouse colon with the detergent benzalkonium chloride (BAC) and followed the ensuing morphologic changes for up to 60 days by using light- and electron microscopy. We found that, 2 days after BAC application, the treated area was essentially devoid of intact nerve elements. From day 7, new nerve fibers were observed within the denervated region. This growth progressed until, at days 30-60, newly grown nerve fibers were present in most of this region, and the pattern of muscle innervation was similar to the normal one. At least part of these fibers originated at neurons within intact ganglia surrounding the denervated region. The cross-sectional area of neurons near the denervated region at day 14 was 52% greater than controls. Glial cells were closely associated with the regenerating nerve fibers. From day 14 onward, we observed undifferentiated cells and differentiating neurons in ganglia surrounding the denervated region, and by day 30, new neurons were present in the myenteric region, along with regenerating nerve fibers. We conclude that the myenteric plexus is endowed with a considerable ability of regeneration and plasticity. The results provide evidence for the presence of stem cells and for an adult neurogenesis in this plexus.

Cholinergic and purinergic contribution to the micturition reflex in conscious rats with long-term bladder outlet obstruction

The urethra of female Wistar rats was partially obstructed for 15 weeks. The effects of atropine (1 mg/kg i.v.), suramin (100 mg/kg i.v.), and a combination of atropine and suramin on the peak micturition pressure (MP) were compared during cystometry in conscious rats controls or subjected to outlet obstruction. On the isolated bladder dome, we studied the inhibitory effect of 1 micromol/L atropine, 1 mmol/L suramin, and the combination of the two drugs on contractions induced by electrical field stimulation (EFS). We studied also the contractile response to 80 mmol/L KCl and the concentration-response curves to noradrenaline, phenylephrine, and carbachol on the bladder dome and bladder neck and alpha, beta-methylene adenosine triphosphate on the bladder dome. In conscious rats, the MP, bladder capacity, and micturition volume were significantly higher in obstructed rats than in controls. Suramin induced the same inhibition in the two groups of animals (-30.7 +/- 13.3% in controls and -29.2 +/- 8.5% in obstructed rats). Atropine decreased the MP, but this effect was twofold greater in obstructed animals (-28.1 +/- 3.1% and -65.1 +/- 6.9% in control and obstructed animals, respectively). However, the combined effect of atropine and suramin was additive in controls but not in obstructed (-56.7 +/- 5.4% and -55.9 +/- 9.4%, respectively). Similar results were obtained in vitro using 1 micromol/L atropine and 1 mmol/L suramin. In the obstructed bladder dome and bladder neck, we found a great reduction in KCl- and carbachol-induced contractility but no difference in the response to EFS. Responses to noradrenaline and phenylephrine were moderately reduced in the bladder neck only, whereas responses to alpha, beta-methylene adenosine triphosphate in the bladder dome were not reduced except at the concentration of 300 micromol/L. We conclude that long-term obstruction in rats could induce cholinergic nerve fiber proliferation as suggested by the decrease in M(3) muscarinic receptor contractility (desensitization) and by a greater sensitivity of the MP to atropine.

The three-dimensional structure of neurons in the guinea pig inferior mesenteric and pelvic hypogastric ganglia

The three-dimensional (3-D) morphology of sympathetic inferior mesenteric ganglion (IMG) neurons and sympathetic-parasympathetic pelvic hypogastric ganglion (PHG) neurons was studied using confocal laser scanning microscopy. Cell bodies of IMG neurons were disc-shaped and were arranged orderly in layers. The dendritic arbor of individual neurons was confined to a plane with a thickness that did not exceed the thickness of the parent cell body. The actual dendritic surface area (71,400 micron 2) and volume (81,500 micron 3) of the IMG neurons were up to 100-fold larger than previously reported for similar sympathetic neurons using data of 2-D measurements and estimations of the third dimension. PHG neurons had a much smaller dendritic surface area (4100 micron 2) and volume (2400 micron 3) compared to IMG neurons. The ratio dendritic/somal surface area for individual IMG and PHG neurons ranged from 5:1 to 14:1 and from 0.1:1 to 6:1, respectively. The total dendritic path-length was 8-42 times greater for IMG than for PHG neurons. Neurons in the IMG were either stellate with radiating dendrites or bipolar-shaped with dendrites emerging from the two poles of the cell body. Neurons in the PHG were of two morphological types. One type (nearly 2/3 of all the imaged PHG neurons) had two to seven relatively long dendrites and an axon; the other type had only one to three short unbranched dendrites and an axon. The spatial organization of neurons within the ganglia and the structural features of individual neurons are likely to have important implications regarding connectivity patterns between neurons within the ganglion as well as on how information is processed by the ganglion.

Stereologic study of the hypothalamic infundibular nucleus in young and older women

Aging in women is associated with dramatic changes in neuronal morphology and neuropeptide gene expression in the medial basal hypothalamus. There is hypertrophy of neurons expressing substance P and neurokinin B gene transcripts in the infundibular (arcuate) nucleus, accompanied by increased tachykinin gene expression. In addition, gonadotropin-releasing hormone (GnRH) gene expression is increased in a separate subpopulation of neurons within the medial basal hypothalamus. In contrast, the number of neurons expressing proopiomelanocortin (POMC) mRNA in the infundibular nucleus of older women is decreased. To determine whether neuronal degeneration contributes to these phenomena, unbiased stereologic methods were used to compare the total number of infundibular neurons between groups of young (premenopausal) and older (postmenopausal) women. There was no significant difference in the total number of infundibular neurons between young (520,000 +/- 42,000 neurons, mean +/- SEM) and older women (505,000 +/- 51,000 neurons, mean +/- SEM). The mean volume of neuronal somata, however, was increased by 40% in the older women (young, 1,860 +/- 180 microm(3) vs. older, 2,610 +/- 230 microm(3), mean +/- SEM, P < 0.05). These data demonstrate that neuronal hypertrophy in older women is not accompanied by degeneration of the infundibular nucleus. We conclude that the loss of menstrual cyclicity in middle-aged women cannot be explained by loss of neurons within the hypothalamic control center for reproduction.

Unusual autonomic ganglia: connections, chemistry, and plasticity of pelvic ganglia

The pelvic ganglia provide the majority of the autonomic nerve supply to reproductive organs, urinary bladder, and lower bowel. Of all autonomic ganglia, they are probably the least understood because in many species their anatomy is particularly complex. Furthermore, they are unusual autonomic ganglia in many ways, including their connections, structure, chemistry, and hormone sensitivity. This review will compare and contrast the normal structure and function of pelvic ganglia with other types of autonomic ganglia (sympathetic, parasympathetic, and enteric). Two aspects of plasticity in the pelvic pathways will also be discussed. First, the influence of gonadal steroids on the maturation and maintenance of pelvic reflex circuits will be considered. Second, the consequences of nerve injury will be discussed, particularly in the context of the pelvic ganglia receiving distributed spinal inputs. The review demonstrates that in many ways the pelvic ganglia differ substantially from other autonomic ganglia. Pelvic ganglia may also provide a useful system in which to study many fundamental neurobiological questions of broader relevance.

Mitochondrial involvement in bladder function and dysfunction

Benign bladder pathology resulting from prostatic hypertrophy or other causes is a significant problem associated with ageing in humans. This condition is characterized by increased bladder mass, decreased urinary flow rate, decreased compliance, and these and other changes in bladder function often subject patients to increased risk of urinary tract infection. While the physiologic attributes of benign bladder pathology have been extensively described in humans and in various animal model systems, the biochemical and molecular genetic bases for that pathology have only recently been investigated in detail. Studies demonstrate that mitochondrial energy production and utilization are severely impaired in bladder smooth muscle during benign bladder disease, and to a large extent this realization has provided a rational basis for understanding the characteristic alterations in urinary flow and compliance in bladder tissue. Recent investigations targeting the detailed molecular basis for impaired mitochondrial function in the disease have shown that performance of the organellar genetic system, and to a large extent that of relevant portions of the nuclear genetic system as well, is severely aberrant in bladder tissue. In this article, we discuss the physiologic aspects of benign bladder disease, summarize biochemical evidence for the altered mitochondrial energy metabolism that appears to underlie bladder pathology, review the structure and function of the mitochondrial genetic system, and discuss molecular genetic studies of that system which have begun to provide a mechanistic explanation for the biochemical and physiological abnormalities that characterize the disease. We also discuss areas for further research which will be critically important in increasing our understanding of the detailed causes of benign bladder pathology.

Does the right side know what the left is doing?

Following peripheral-nerve lesions there are well-documented events that affect the contralateral nonlesioned structures. These contralateral effects are qualitatively similar to those occurring at the ipsilateral side, but are usually smaller in magnitude and have a briefer time course. It is unclear whether the findings are an epiphenomenon or serve a biological purpose, but in either case the existence of these effects implies the presence of unrecognized signalling mechanisms that link the two sides of the body. Strong circumstantial evidence argues against a peripheral mechanism (for example, via circulating factors) and in favour of a central mechanism, in particular signalling via the system of commissural interneurons that is present in spinal cord and brainstem. While an altered pattern of activity in this system might underlie the phenomenon, there are several reasons for proposing that the changes depend upon chemical signals, possibly growth factors. Because of its relative easy access for experimental manipulation, the spinal cord could serve as a model system to study these transmedian signalling systems.

In oculo transplants of myometrium from postpartum guinea pigs fail to support sympathetic reinnervation

Sympathetic nerves to the enlarged fetus-containing region of the uterus undergo degenerative changes during late pregnancy and show slow regrowth after parturition. It is not known whether this unusual response of sympathetic nerves to smooth muscle hypertrophy is due to the sensitivity of short adrenergic neurons to hormonal changes, or whether the nerves respond to changes in the neurotrophic capacity of the target. We have investigated this question using in oculo transplantation. Small pieces of myometrium from the uterine horn of virgin guinea pigs, or from the region previously occupied by the placenta and fetus in postpartum guinea pigs, were transplanted into the anterior eye chamber. After 3 wk in oculo, the pattern of reinnervation of the transplants was assessed on whole mount stretch preparations stained for tyrosine hydroxylase. The histology of the transplants was examined in toluidine blue-stained semithin sections. Myometrial transplants from virgin donors and uterine artery transplants from both virgin and postpartum donors became organotypically reinnervated by sympathetic fibres from the host iris. In contrast, sympathetic nerves did not reinnervate myometrial transplants from postpartum donors, although they approached the transplants and became distributed in the surrounding connective tissue. All transplanted tissues showed a normal histological appearance. Both the myometrium and uterine artery from postpartum donors retained a hypertrophic appearance after 3 wk in oculo. We interpret these results to indicate that the degeneration of sympathetic nerves in late pregnancy, as well as their slow regrowth to the uterus after delivery, may be due to changes in uterine smooth muscle rather than a particular sensitivity of short adrenergic neurons to hormonal changes.

Specific targeting of ganglion cell sprouts provides an additional mechanism for restoring peripheral motor circuits in pelvic ganglia after spinal nerve damage

The pelvic ganglia contain both sympathetic and parasympathetic neurons and provide an interesting model in which to study the effects of a distributed spinal nerve lesion. Previous animal studies have suggested that after either lumbar or sacral nerve injury, some functional connections are restored between preganglionic and postganglionic neurons. It has been proposed that this is because of intact preganglionic axons sprouting collaterals to supply denervated ganglion cells. However, this has never been demonstrated, and our study has investigated whether the ganglion cells themselves contribute to axogenesis and restoration of peripheral circuitry. We have monitored the growth of axons from pelvic ganglion cells after lumbar or sacral nerve injury (partial decentralization), or a combination of the two (total decentralization). These new processes were distinguished from intact preganglionic terminals by their immunoreactivity for substances present only in pelvic ganglion neurons (vasoactive intestinal peptide, neuropeptide Y, and tyrosine hydroxylase). The proportion of pelvic neurons surrounded by these immunostained fibers was then assessed. Complete removal of preganglionic terminals provides the biggest stimulus for growth of new axon processes (sprouts), which grow profusely within just a few days. These arise from each of the main chemical classes of pelvic neurons but grow at different rates and have different distributions. Importantly, some chemical classes of sprouts preferentially supply neurons of dissimilar histochemistry, suggesting the presence of very specific targeting mechanisms rather than random growth. These sprouts are transient, however, those formed after partial decentralization appear to be maintained. Moreover, after lesion of either lumbar or sacral spinal nerves, many sprouts arise from neurons with intact spinal connections and innervate neurons that have lost their preganglionic inputs. This provides a very different alternative mechanism to reestablish communication between preganglionic and postganglionic neurons. In conclusion, we have demonstrated a rapid and selective axogenesis within the pelvic ganglion after spinal nerve injury. This may allow the development of novel strategies by which autonomic nerve pathways can be experimentally manipulated, to facilitate more rapid return of appropriate peripheral reflex control.

Homotransplant of pelvic ganglion into bladder wall in adult rats

In these experiments a large portion of the pelvic ganglion of adult female rats was transplanted into the wall of the urinary bladder of the same animals. The morphology and fine structure of the transplants were studied in whole-mounts and in sections for light and electron microscopy, from two days up to four months after operation. The general architecture of the ganglion was preserved in all the transplants. The vascularization was re-established. Nerves grew out of the transplant and connections with the original intramural nerves of the bladder wall were established. All the synapses degenerated at the time of transplantation; new synapses began to reappear on the ganglion neurons in the oldest transplants. Although some neurons in the transplant degenerated during the first few days, the majority of neurons survived for the full length of the experiments (four months). Satellite glial cells and small intensely fluorescent cells had a similar structure and distribution as in control ganglia. The results show that the homotransplant of pelvic neurons into the bladder has a high rate of success, in terms of survival, maintenance of fine structure, growth and re-connections; these neurons of adult organisms display plastic and regenerative abilities.

Nitrergic and cholinergic innervation of the rat lower urinary tract after pelvic ganglionectomy

The possible coexistence of nitric oxide (NO) and acetylcholine in the rat major pelvic ganglion (MPG) was examined by double immunohistochemistry using antisera raised against NO synthase (NOS) and choline acetyltransferase (ChAT). The smooth muscle responses of the isolated bladder and urethra were recorded after bilateral cryoganglionectomy of the MPG, focusing on the possible development of denervation supersensitivity. In the MPG, NOS immunoreactivity (ir) was seen in a large number of cell bodies, but it was not as abundant as ChAT-ir cell bodies. Double immunolabeling showed that all NOS-ir cell bodies also displayed ChAT-ir. In ganglionectomized bladders, the electrical field stimulation (EFS)-evoked contractile response was markedly reduced. When compared with control bladders, detrusor strips from ganglionectomized rats were more sensitive to carbachol as revealed by a lower negative logarithm of the drug concentration eliciting 50% relaxation (6.5 +/- 0.04 vs. 5.9 +/- 0.07). In the urethra, the NO-mediated relaxant response to EFS was practically abolished by ganglionectomy, whereas no difference was found in sensitivity to 3-morpholinosydnonimine hydrochloride (SIN-1). SIN-1 produced an equal increase in tissue levels of guanosine 3',5'-cyclic monophosphate in urethral preparations from control and ganglionectomized rats. The results suggest that the NOS-ir nerves that mediate inhibition of rat urethral smooth muscle tone originate from the MPG and contain ChAT. No denervation supersensitivity to nitrergic stimulation was observed in the urethra after ganglionectomy.

Plasticity in adult and ageing sympathetic neurons

The nature of neural plasticity and the factors that influence it vary throughout life. Adult neurons undergo extensive and continual adaptation in response to demands that are quite different from those of early development. We review the main influences on the survival, growth and neurotransmitter expression in adult and ageing sympathetic neurons, comparing these influences to those at work in early development. This "developmental" approach is proposed because, despite the contrasting needs of different phases of development, each phase has a profound influence on the mechanisms of plasticity available to its successors. Interactions between neurons and their targets, whether effector cells or other neurons, are vital to all of these aspects of neural plasticity. Sympathetic neurons require access to target-derived diffusible neurotrophic factors such as NGF, NT3 and GDNF, as well as to bound elements of the extracellular matrix such as laminin. These factors probably influence plasticity throughout life. In adult life, and even in old age, sympathetic neurons are relatively resistant to cell death. However, they continue to require target-derived diffusible and bound factors for their maintenance, growth and neurotransmitter expression. Failure to maintain appropriate neuronal function in old age, for example in the breakdown of homeostasis, may result partly from a disturbance of the dynamic, trophic relationship between neurons and their targets. However, there is no clear evidence that this is due to a failure of targets to synthesize neurotrophic factors. On the neural side of the equation, altered responsiveness of sympathetic neurons to neurotrophic factors suggests that expression of the trk and p75 neurotrophin receptors contributes to neuronal survival, maintenance and growth in adulthood and old age. Altered receptor expression may therefore underlie the selective vulnerability of some sympathetic neurons in old age. The role of neural connectivity and activity in the regulation of synthesis of target-derived factors, as well as in neurotransmitter dynamics, is reviewed.

Restoration of rat bladder function following release of short- and long-term partial outflow obstruction

Detrusor dysfunction does not recover in some patients with benign prostatic hyperplasia (BPH) even after prostate resection. 'We studied the functional restoration of the rat bladder after release of short- or long-term outflow obstruction. Bladder function was assessed by in vivo infusion cystometry and an in vitro organ bath technique. There were no significant differences in bladder weight and contractile strength induced by stimuli in detrusor muscle strips from obstructed rats and age-matched control rats. After short-term obstruction the whole bladder pressure generated in vitro by field stimulation, bethanechol, ATP, and KCl completely recovered to control levels. In contrast, after long-term obstruction, the whole bladder pressure in response to field stimulation remained significantly lower than in controls. Infusion cystometry variables, including the pressure at which micturition was induced, maximal voiding pressure, capacity, and residual urine volume, were similar between controls and rats subjected to short-term obstruction. However, the maximal voiding pressure after long-term obstruction was significantly less than that of controls.

Light, electron, and confocal microscopic study of the mouse superior mesenteric ganglion

The superior mesenteric ganglion (S.m.g.), a sympathetic prevertebral ganglion, is an integrating center for gastrointestinal reflexes. Many details of its structure are still lacking. In the present study, mouse S.m.g. neurons were studied by light, electron, and confocal microscopy. Neurons had an average of 5-6 primary dendrites. Total dendritic length averaged 963 microns. Confocal microscopy and three-dimensional reconstructed images revealed cell body surface features, precise location where axons and dendrites emerged from it, cell body size, and extent of dendritic projection in three axes. Cell body diameter and dendritic projections were less in the dorsoventral than in the rostrocaudal or mediolateral axes. Cell body surface area and volume averaged 4,271 microns 2 and 4,908 microns 3, respectively. Dendritic surface areas and volumes were 5-6 times larger. Two main neuron types (projecting caudally or rostrally) were distinguished. The former were found throughout the S.m.g., whereas the latter were found only in the cephalad region, comprising about 40% of neurons found there. Rostrally projecting neurons had fewer primary dendrites, fewer total dendritic branches, and shorter total dendritic length than caudally projecting neurons. There were regional differences in percentage of neurons responding to electrical stimulation of left or right hypogastric, lumbar colonic, or left splanchnic nerves but not in nerve fibers connecting the S.m.g. and celiac ganglion. A greater percentage of caudally than rostrally projecting cephalad neurons responded to stimulation of any nerve trunk. These results indicate that the mouse S.m.g. contains at least two distinct types of neurons that differ in their morphology and their source of preganglionic synaptic input.

Nitric oxide synthase-immunoreactive, adrenergic, cholinergic, and peptidergic nerves of the female rat urinary tract: a comparative study

The distribution and frequency of NO synthase (NOS)-immunoreactive (IR) nerves in relation to the general autonomic innervation, adrenergic, cholinergic and some peptidergic nerves, were investigated in the female rat urinary tract. NOS nerves were very frequent in the smooth musculature of the urethra together with cholinergic, adrenergic and neuropeptide Y (NPY)-IR nerves, whereas vasoactive intestinal peptide (VIP)-IR and calcitonin-gene-related peptide (CGRP)-IR nerves were much less abundant. NOS-IR, CGRP-IR and cholinergic nerves were also frequent in the longitudinal smooth musculature of the distal ureters and the ureteral orifices into the bladder, where no adrenergic, NPY-IR and VIP-IR nerves were found. In contrast, in the detrusor NOS-IR nerves were scarce. Bilateral pelvic ganglionectomy very pronouncedly decreased the number of any of the populations of nerves studied, whereas bilateral pelvic decentralization selectively reduced the number of CGRP-IR nerves in all structures and locations. Outflow obstruction very overtly reduced the number of NOS-IR nerves in parallel with the general autonomic innervation. Thus, in the rat female urinary tract, NOS-containing nerves particularly occur in regions with sphincteric functions such as urethra and ureteric orifices. In these regions NO may exert a transmitter role, both directly or by interaction with other transmitters/modulators.

Lactate dehydrogenase activity and isoform distribution in the rat pelvic ganglion: effects of diabetes and bladder outlet obstruction

We have previously shown that the intramural motor nerves in the rat bladder can function in anoxic conditions. The present study aims to explore the distribution and activity of lactate dehydrogenase (LDH), the key enzyme for ATP generation in anoxia. The activity and isoform distribution pattern of LDH was studied in pelvic ganglia from male and female rats. A histochemical investigation showed that the LDH activity was intense in the ganglion cells, and weak in the other tissue components (nerve bundles, connective tissue). The male pelvic ganglion weighted 55% more than the female pelvic ganglion, the enzyme activity per unit ganglion weight was 60% higher and the total LDH activity was 155% higher. The isoform distribution was similar, with M4 being dominant isoform, followed by M3H. Infravesical outlet obstruction in the female rat induced a threefold increase in ganglion weight, and the total LDH activity increased twofold. In this hypertrophic female ganglion a decreased relative amount of M4, and an increased amount of MH3, was found. Diabetes in the male rat had no effect on ganglion weight or its contents and isoform distribution of LDH.

Influence of spinal cord injury on the morphology of bladder afferent and efferent neurons

Severe micturition dysfunction can occur following spinal cord injury (SCI) due to abnormal contractions of the urethral sphincter during bladder contractions (bladder/sphincter dyssynergia). This causes urinary retention, bladder overdistension, and increases the workload of the bladder leading to hypertrophy of the bladder muscle. Bladder hypertrophy induced by urethral outlet ligation in rats is accompanied by enlargement of both the afferent and efferent neurons innervating the bladder. The primary aim of this study was to test whether SCI-induced bladder hypertrophy produces a similar enlargement of bladder afferent neurons in the dorsal root ganglia (DRG) or efferent neurons in the major pelvic ganglia (MPG). Following SCI in female Wistar rats, there was a four-fold increase in bladder weight. The mean cross-sectional area of bladder DRG cell profiles increased approx. 50% after SCI; however, the mean area of MPG cell profiles did not change significantly. Urinary diversion (disconnecting the ureters from the bladder) prevented both the bladder hypertrophy and the DRG cell hypertrophy after SCI, suggesting that bladder hypertrophy drives DRG cell enlargement. On the other hand, since the size of MPG cells did not change significantly after SCI, bladder hypertrophy does not mandate MPG cell enlargement. However, preliminary results indicate that the mean cross-sectional area of MPG cells did increase (2-3 times) in SCI rats when the neural input to the MPG was eliminated by transecting the pelvic and hypogastric nerves; this suggests that the lack of change in size of MPG cells after SCI may be due to an inhibitory influence from the spinal cord.

Neural input regulates tissue NGF and growth of the adult rat urinary bladder

To gain insight into the effect of innervation on neurotrophin production, NGF levels in the urinary bladder were measured following unilateral ganglionectomy (bladder denervation) or separation of the post-ganglionic bladder neurons from the central nervous system of the adult rat (bladder and ganglion decentralization). These interruptions of the neural input to half of the bladder caused histological evidence of smooth muscle growth, increased bladder weight (denervation-3 weeks: 98.6 +/- 6 mg; decentralization-3 weeks: 94.0 +/- 7 mg vs. control: 79.6 +/- 4 mg, P < 0.05), transient increases in tissue NGF up to 10-fold (1.99 +/- 0.65 pg NGF/bladder control vs. 20.24 +/- 0.53 (P < 0.05) denervated, ipsilateral, 1 week) and hypertrophy of the neurons in the pelvic ganglia supplying the bladder (control: 340 +/- 4.4 microns2; denervated-3 weeks: 530 +/- 6.8 microns2, P < 0.05; decentralized-3 weeks: 463 +/- 6.8 microns2, P < 0.05). These data suggest that neural input has a significant role in regulating growth of the bladder. Furthermore, the findings show that innervation influences tissue levels of NGF in the bladder.

Reversal of muscle hypertrophy in the rat urinary bladder after removal of urethral obstruction

We studied the ultrastructure of the bladder musculature after first inducing hypertrophy by means of urethral obstruction and subsequently removing the obstruction. With hypertrophy the bladder musculature increases ten-fold or more in volume; after de-obstruction approximately 4/5 of the hypertrophic muscle weight and volume is lost within six weeks. In spite of this very large decrease in muscle mass there is no degeneration of muscle cells or nerve endings or of other cell types in the de-obstructed bladder either at 5 days or at 6 weeks. The individual muscle cells are smaller in size than in the hypertrophic bladder but still larger than control muscle cells. The decrease in muscle cell size is more substantial than the decrease in muscle cell surface. There are no lysosomes or other signs of intracellular degradation in any cells of the muscle layer. The musculature contains a very large amount of intercellular material, mainly collagen. This study documents the great plasticity of the musculature in the reduction of muscle mass after de-obstruction. However, some of the fine structural features are almost as different from the controls as in the hypertrophic muscle.

Regulation of vasoactive intestinal peptide expression in sympathetic neurons in culture and after axotomy: the role of cholinergic differentiation factor/leukemia inhibitory factor

Vasoactive intestinal peptide (VIP) expression increases in sympathetic neurons when they are grown in dissociated cell or explant cultures and when they are axotomized in vivo. In dissociated cell culture, the magnitude of the VIP increase was reduced when nonneuronal cells were removed and medium conditioned by ganglionic nonneuronal cells increased VIP in neuron-enriched cultures. Antiserum against cholinergic differentiation factor (also leukemia inhibitory factor; CDF/LIF), but not against ciliary neurotrophic factor, immunoprecipitated this activity. Medium conditioned by sympathetic ganglion explants also contained a VIP-stimulatory molecule that was immunoprecipitated by CDF/LIF antiserum, and CDF/LIF antiserum partially blocked VIP induction in explants. CDF/LIF mRNA was increased in dissociated cell cultures, in ganglion explants and in vivo after axotomy. Our results suggest that CDF/LIF released from ganglionic nonneuronal cells plays an important role in regulating VIP after axotomy.

Alterations in neural pathways to the urinary bladder of the rat in response to streptozotocin-induced diabetes

Voiding dysfunction in diabetics has been attributed to a variety of causes including an axonopathy in autonomic pathways to the urinary bladder. The present study was undertaken to determine whether changes occurred in afferent and efferent neurons supplying bladders of streptozotocin (STZ)-induced diabetic rats. Nine weeks after STZ treatment, the mean cross-sectional area for retrogradely labeled (Fluoro-Gold) bladder neurons in the major pelvic ganglion (MPG) was greater in diabetics (364 microns 2) than controls (300 microns 2). The number of labeled neurons was similar in these groups. In contrast, mean cross-sectional areas of bladder afferent neurons labeled with WGA-HRP in the L6 and S1 dorsal root ganglia (DRG) were smaller (393 microns 2) in diabetics than in normal rats (528 microns 2). In addition, very few DRG neurons were labeled in STZ-treated rats and transganglionic labeling of bladder afferent projections in the L6 and S1 spinal cord with WGA-HRP was sparse. Radioimmunoassay studies revealed that substance P was reduced by 70% in the MPG and by 40% in L6 DRG, yet this peptide was unchanged in the bladders of diabetic rats. The amounts of VIP in the MPG and DRG of diabetics and controls were similar, while VIP in the bladder was increased in diabetics. These observations indicate that both afferent and efferent neurons innervating the urinary bladder are altered in the STZ-induced diabetic rat. In addition, axonal transport in visceral afferent pathways may be disrupted.

Rat: overview and innervation

Despite the development of molecular and cellular methods for examining physiological processes, the use of the whole animal model remains essential to advance knowledge regarding the integration and coordination of events associated with urinary tract function. The rat offers an inexpensive and versatile species to investigate bladder and urethral responses to drugs or pathology. Models for many disorders have been developed in rodents including diabetes, multiple sclerosis, spinal cord injury, Parkinson's disease, bladder outlet obstruction, pain, and aging. This review examines methodologies to evaluate lower urinary tract function and manipulations used to create pathological models in rodents.

Effect and content of arginine vasopressin in normal and obstructed rat urinary bladder: an in vivo and in vitro investigation

The present investigation was performed to evaluate the possible role of arginine vasopressin (AVP) in detrusor instability in the obstructed rat urinary bladder. The effect of AVP on normal and obstructed rat detrusor smooth muscle was tested in vivo and in vitro. Arginine vasopressin given as a closed intraarterial injection to the bladder transiently decreased micturition volume and increased micturition frequency during cystometry in control rats. In rats with infravesical outlet obstruction the effect of AVP on cystometrical parameters was negligible. In accordance with this finding, the efficacy of AVP in contracting detrusor muscle in vitro was much lower for obstructed bladders than for controls. The EC50 values were, however, similar. Arginine vasopressin added to the bath had no effect on nerve-mediated contractile responses. Obstruction led to a transient decrease in immunoreactive AVP concentration, but the total amount of AVP per bladder increased significantly after 6 weeks of obstruction as a consequence of the 14-fold increase in bladder weight. The decreased excitatory effect of AVP in obstructed bladder makes a role for this peptide in the development of detrusor instability less likely.

Effect of decentralization or contralateral ganglionectomy on obstruction-induced hypertrophy of rat urinary bladder muscle and pelvic ganglion

After urethral obstruction the musculature of the rat urinary bladder undergoes extensive hypertrophy, irrespective of whether its innervation is intact or whether one of the two pelvic ganglia has been decentralized or excised. Even the excision of both ganglia does not inhibit muscle hypertrophy. The presence of nerves is not a prerequisite for the muscle growth to occur. The stimulus for growth resides in the bladder itself, and the present and previous observations are in agreement with the notion that the distension of the muscle is a primary stimulus for muscle growth. With bladder hypertrophy, the pelvic ganglion neurons undergo hypertrophy, even when they are devoid of their preganglionic input. Synaptic connection with the preganglionic fibres and stimuli from the spinal cord are not prerequisites for neuronal hypertrophy. However, the hypertrophy is less marked in the decentralized ganglion neurons than in the neurons of the contralateral intact ganglion. With bladder hypertrophy and contralateral ganglionectomy, the neuronal hypertrophy is greater than with either procedure alone, suggesting that the two forms of neuronal growth stimulation can be added to each other.