Mechanisms underlying the pathogenesis of urinary bladder instability - new perspectives for the treatment of reflex incontinence

The urine storage ability of the urinary bladder is markedly impaired following inflammation of the urinary bladder and spinal cord injury because of a hyperexcitability of micturition reflexes. Using two rat models of inflammation-induced bladder overactivity and detrusor hyper-reflexia following spinal cord injury we investigated changes in the neuronal pathways to the urinary bladder which may underlie the development of this instability. Our results suggest that among the factors involved in inflammation-induced bladder instability are significant changes in the expression of the neuropeptides substance P, calcitonin gene-related peptide and galanin at the primary afferent level, as well as of the enzyme neuronal nitric oxide synthase (nNOS) at the afferent and postganglionic efferent level. In the lumbar and sacral spinal cord nNOS-immunoreactivity was depleted from dorsal horn neurones in both cystitis and spinal cord injured rats and from preganglionic parasympathetic neurones after spinal cord injury. Distension of the bladder in chronically spinalized rats elicited c-Fos expression in a significantly greater number of neurones throughout the lumbar and sacral segments than in rats with an intact neuraxis. Thus, under pathological conditions rather complicated changes in the synthesis of neuropeptides and nNOS occur at the primary afferent, spinal cord and postganglionic efferent level that together control the activity of the urinary bladder. Further mechanisms like unmasking of silent synapses and axonal sprouting in the spinal cord might further contribute to an increase in activity in micturition reflex pathways. Local cooling of the dorsal spinal cord at the level L6/S1 with temperatures between 14 and 20 degrees C proved a simple technique to control the unstable bladder and restore continence in both inflammation-induced detrusor overactivity and detrusor hyperreflexia following spinal cord injury. The effects of cooling are probably the result of a blockade of synaptic transmission within the dorsal cord which eliminates neuronal overactivity. Thus, local spinal cord cooling could offer a new method to treat bladder instability and reflex incontinence.     

Pharmacologic and potential biologic interventions to restore bladder function after spinal cord injury

Spinal cord injury disrupts voluntary control of voiding and the normal reflex pathways that coordinate bladder and urethral sphincter function. The present review addresses studies in animals and humans that have evaluated various therapeutic approaches for normalizing lower urinary tract function after spinal cord injury.     

Mechanisms underlying the pathogenesis of urinary bladder instability - new perspectives for the treatment of reflex incontinence

The urine storage ability of the urinary bladder is markedly impaired following inflammation of the urinary bladder and spinal cord injury because of a hyperexcitability of micturition reflexes. Using two rat models of inflammation-induced bladder overactivity and detrusor hyper-reflexia following spinal cord injury we investigated changes in the neuronal pathways to the urinary bladder which may underlie the development of this instability. Our results suggest that among the factors involved in inflammation-induced bladder instability are significant changes in the expression of the neuropeptides substance P, calcitonin gene-related peptide and galanin at the primary afferent level, as well as of the enzyme neuronal nitric oxide synthase (nNOS) at the afferent and postganglionic efferent level. In the lumbar and sacral spinal cord nNOS-immunoreactivity was depleted from dorsal horn neurones in both cystitis and spinal cord injured rats and from preganglionic parasympathetic neurones after spinal cord injury. Distension of the bladder in chronically spinalized rats elicited c-Fos expression in a significantly greater number of neurones throughout the lumbar and sacral segments than in rats with an intact neuraxis. Thus, under pathological conditions rather complicated changes in the synthesis of neuropeptides and nNOS occur at the primary afferent, spinal cord and postganglionic efferent level that together control the activity of the urinary bladder. Further mechanisms like unmasking of silent synapses and axonal sprouting in the spinal cord might further contribute to an increase in activity in micturition reflex pathways. Local cooling of the dorsal spinal cord at the level L6/S1 with temperatures between 14 and 20 °C proved a simple technique to control the unstable bladder and restore continence in both inflammation-induced detrusor overactivity and detrusor hyperreflexia following spinal cord injury. The effects of cooling are probably the result of a blockade of synaptic transmission within the dorsal cord which eliminates neuronal overactivity. Thus, local spinal cord cooling could offer a new method to treat bladder instability and reflex incontinence.     

Increased expression of neuronal nitric oxide synthase in bladder afferent cells in the lumbosacral dorsal root ganglia after chronic bladder outflow obstruction

Nitric oxide (NO), a neurotransmitter in autonomic reflex pathways, plays a role in functional neuroregulation of the lower urinary tract. Upregulation of the levels of neuronal nitric oxide synthase (nNOS), the enzyme system responsible for NO synthesis, has been documented in the peripheral, spinal and supraspinal segments of the micturition reflex in diseases such as cystitis, bladder/sphincter dyssynergia following spinal cord injury and bladder overactivity after cerebral infarction. These observations suggest that NO might play a role in the development of bladder overactivity. In this study, nNOS-immunoreactivity (IR) was evaluated in bladder afferent and spinal neurons following bladder outflow obstruction (BOO) in male and female rats. Chronic BOO was induced by placing lumen reducing ligatures around the proximal urethra. Six weeks following the obstructive or sham surgery, bladder function was evaluated by awake cystometry. Bladder afferent neurons in L1, L2, L6 and S1 dorsal root ganglia (DRG) were identified by retrograde neuronal labeling with injection of Fast Blue into the bladder smooth muscle. A differential distribution of nNOS-IR was subsequently evaluated in bladder afferent neurons in the DRG and in the associated spinal cord segments. The percentage of bladder afferent neurons expressing nNOS-IR was increased in L6 (1.8-fold in males and 1.9-fold in females) and S1 (2.8-fold in males and 5.3-fold in females) DRG. In contrast, no changes in nNOS-IR in neurons or fiber distribution were observed in any spinal cord segments examined.     

Changes in urinary bladder neurotrophic factor mRNA and NGF protein following urinary bladder dysfunction

Spinal cord injury and cyclophosphamide-induced cystitis dramatically alter lower urinary tract function and produce neurochemical, electrophysiological, and anatomical changes that may contribute to reorganization of the micturition reflex. Mechanisms underlying this neural plasticity may involve alterations in neurotrophic factors in the urinary bladder. These studies have determined neurotrophic factors in the urinary bladder that may contribute to reorganization of the micturition reflex following cystitis or spinal cord injury. A ribonuclease protection assay was used to measure changes in urinary bladder neurotrophic factor mRNA (betaNGF, BDNF, GDNF, CNTF, NT-3, and NT-4) following spinal cord injury (acute/chronic) or cyclophosphamide-induced cystitis (acute/chronic). The correlation between urinary bladder nerve growth factor mRNA and nerve growth factor protein expression was also determined. Each experimental paradigm resulted in significant (P 相似文献   

Artificial autonomic reflexes: using functional electrical stimulation to mimic bladder reflexes after injury or disease

Autonomic reflexes controlling bladder storage (continence) and emptying (micturition) involve spinal and supraspinal nerve pathways, with complex mechanisms coordinating smooth muscle activity of the lower urinary tract with voluntary muscle activity of the external urethral sphincter (EUS). These reflexes can be severely disrupted by various diseases and by neurotrauma, particularly spinal cord injury (SCI). Functional electrical stimulation (FES) refers to a group of techniques that involve application of low levels of electrical current to artificially induce or modify nerve activation or muscle contraction, in order to restore function, improve health or rectify physiological dysfunction. Various types of FES have been developed specifically for improving bladder function and while successful for many urological patients, still require substantial refinement for use after spinal cord injury. Improved knowledge of the neural circuitry and physiology of human bladder reflexes, and the mechanisms by which various types of FES alter spinal outflow, is urgently required. Following spinal cord injury, physical and chemical changes occur within peripheral, spinal and supraspinal components of bladder reflex circuitry. Better understanding of this plasticity may determine the most suitable methods of FES at particular times after injury, or may lead to new FES approaches that exploit this remodeling or perhaps even influence the plasticity. Advances in studies of the neuroanatomy, neurophysiology and plasticity of lumbosacral nerve circuits will provide many further opportunities to improve FES approaches, and will provide "artificial autonomic reflexes" that much more closely resemble the original, healthy neuronal regulatory mechanisms.     

The Role of Vasoactive Intestinal Polypeptide and Pituitary Adenylate Cyclase-Activating Polypeptide in the Neural Pathways Controlling the Lower Urinary Tract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in the neural pathways regulating the lower urinary tract. VIP-immunoreactivity (IR) is present in afferent and autonomic efferent neurons innervating the bladder and urethra, whereas PACAP-IR is present primarily in afferent neurons. Exogenously applied VIP relaxes bladder and urethral smooth muscle and excites parasympathetic neurons in bladder ganglia. PACAP relaxes bladder and urethral smooth muscle in some species (pig) but excites the smooth muscle in other species (mouse). Intrathecal administration of VIP in cats with an intact spinal cord suppresses reflex bladder activity, but intrathecal administration of VIP or PACAP in rats enhances bladder activity and suppresses urethral sphincter activity. PACAP has presynaptic facilitatory effects and direct excitatory effects on lumbosacral parasympathetic preganglionic neurons. Chronic spinal cord transection produces an expansion of VIP-IR (cats) and PACAP-IR (rats) in primary afferent axons in the lumbosacral spinal cord and unmasks spinal excitatory effects of VIP on bladder reflexes in cats. Intrathecal administration of PACAP6-38, a PAC1 receptor antagonist, reduces bladder hyperactivity in chronic spinal-cord-injured rats. These observations raise the possibility that VIP or PACAP have a role in the control of normal or abnormal voiding.     

Reflex inhibition of urethral sphincters to permit voiding in paraplegia

When the spinal motoneurons innervating the external sphincter of the urethra cannot be inhibited voluntarily due to lesions of the spinal cord, the normal capacity to relax this physiologic valve during micturition is lost. Even if contractions of the bladder occur, urinary outflow may be completely blocked at the sphincter, leading to distention of the bladder and the risk of urinary infection. A method is described for controllably relaxing the sphincter, which permits free outflow of urine in paraplegic cats. One pudendal nerve is sectioned, paralyzing half of the sphincter, but leaving the experimental animals entirely continent. The motoneurons supplying the other half of the sphincter are inhibited by means of spinal reflexes, eliminating active resistance to urethral flow. The simplicity of this approach suggests that it may prove equally effective in human paraplegia.     

Principles of Sacral Nerve Stimulation (SNS) for the Treatment of Bladder and Urethral Sphincter Dysfunctions

Objectives. Sacral nerve stimulation (SNS) (Medtronic, Inc., Minneapolis, MN) is an exciting new treatment for refractory voiding disorders including urinary incontinence, retention, and voiding dysfunction. It is known that both voiding and continence reflex mechanisms are organized in the sacral spinal cord and that pathologic conditions can alter the balance between these two opposing mechanisms. Methods. The background and surgical technique of SNS will be presented. This will be followed by a discussion of hypotheses on how SNS works. Results. The beneficial effects of SNS are most reasonably attributed to activation of somatic afferent axons in the sacral spinal roots. This evoked afferent activity in turn modulates sensory processing and micturition reflex pathways in the spinal cord. Hyperactive voiding can be suppressed by direct inhibition of bladder preganglionic neurons as well as inhibition of interneuroneal transmission in the afferent limb of the micturition reflex. On the other hand, voiding in patients with urinary retention can be facilitated by inhibition of reflex pathways to the urethral outlet (guarding reflexes). Conclusions. SNS, a nonablative, minimally invasive technique for urologists, holds great promise for a large number of patients who suffer debilitating and refractory urinary symptoms.     

Increased expression of growth-associated protein (GAP-43) in lower urinary tract pathways following cyclophosphamide (CYP)-induced cystitis

Alterations in the expression of growth-associated protein 43 (GAP-43) were examined in lower urinary tract micturition reflex pathways in a chronic model of cyclophosphamide (CYP)-induced cystitis. In control animals, expression of GAP-43 was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure; (2) the dorsal horn and (3) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (L6-S1) and (4) in the lateral collateral pathway of Lissauer in L6-S1 spinal segments. Densitometry analysis has demonstrated significant increases (p相似文献   

Fluoxetine,a selective serotonin reuptake inhibitor used clinically,improves bladder function in a mouse model of moderate spinal cord injury

After spinal cord injury,the upward conduction of the spinal cord is lost,resulting in the loss of micturition control,which manifests as detrusor sphincter dyssynergia and insufficient micturition.Studies have shown that serotonergic axons play important roles in the control of the descending urination tract.In this study,mouse models of moderate spinal cord contusions were established.The serotonin agonists quipazine(0.2 mg/kg),8-hydroxy-2-(di-n-propylamino)tetralin(8-OH-DAPT,0.1 mg/kg),buspirone(1 mg/kg),sumatriptan(1 mg/kg),and rizatriptan(50 mg/kg),the serotonin reuptake inhibitors fluoxetine(20 mg/kg)and duloxetine(1 mg/kg),and the dopamine receptor agonist SKF-82197(0.1 mg/kg)were intraperitoneally administered to the model mice 35 days post-injury in an acute manner.The voided stain on paper method and urodynamics revealed that fluoxetine reduced the amount of residual urine in the bladder and decreased bladder and external urethral sphincter pressure in a mouse model of moderate spinal cord injury.However,fluoxetine did not improve the micturition function in a mouse model of severe spinal cord injury.In contrast,the other serotonergic drugs had no effects on the micturition functions of spinal cord injury model mice.This study was ethically approved by the Institutional Animal Care and Use Committee of Jiangsu Province Hospital of Chinese Medicine(approval No.2020DW-20-02)on September 11,2020.     

The role of 5-HT(1A) receptors in control of lower urinary tract function in cats

In the present study, the role of 5-HT(1A) receptors in control of lower urinary tract function in cats was examined using 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) as agonists and WAY100635 and LY206130 as antagonists. Bladder function was assessed using cystometric infusion of saline or 0.5% acetic acid to produce bladder irritation. External urethral sphincter (EUS) function was assessed using electromyographic (EMG) recordings of activity recorded during cystometry or by recording electrically evoked pudendal reflexes. Both 5-HT(1A) receptor agonists caused dose-dependent decreases in bladder activity and increases in EUS EMG activity under conditions of acetic acid infusion. 5-HT(1A) receptor antagonists reversed both the bladder-inhibitory and sphincter-facilitatory effects. Thus, 5-HT(1A) receptor activation can have opposite effects on nociceptive afferent processing depending upon the efferent response being measured. During saline infusion of the bladder, 8-OH-DPAT produced moderate inhibition of bladder activity and had no significant effect on sphincter electromyographic (EMG) activity. 8-OH-DPAT either had no effect, or inhibited, low-threshold electrically evoked pudendal reflexes. These findings indicate that 5-HT(1A) receptor stimulation is inhibitory to bladder function in cats, especially under conditions where the bladder is hyperactive due to irritation. Furthermore, these bladder-inhibitory effects are the exact opposite of the bladder-excitatory effects of 8-OH-DPAT reported in rats. 5-HT(1A) receptor stimulation increases EUS motoneuron activity when driven by nociceptive bladder afferent inputs but not when driven by non-nociceptive afferent inputs. In summary, 5-HT(1A) receptor agonists facilitate a nociceptor-driven spinal reflex (sphincter activity) but inhibit a nociceptor-driven supraspinal reflex (micturition). This pattern of activity would facilitate urine storage and may be important under 'fight-or-flight' conditions when serotonergic activity is high.     

Transmission of afferent information from urinary bladder, urethra and perineum to periaqueductal gray of cat

The micturition reflex pathway is a supraspinal pathway. Anatomical tracing evidence is compatible with an involvement of the periaqueductal gray (PAG) in the ascending limb of this reflex. We tested the involvement of the PAG in receiving urinary tract- or perineum-related information and attempted to characterize this ascending path in terms of what type of information is being conveyed. Electrical stimulation of the pelvic nerves, which carry afferent information from the urinary bladder, evoked maximum field potentials in the caudal third of the PAG, primarily in the dorsal part of the lateral PAG and in the ventrolateral PAG. Since the regions activated by pelvic nerve stimulation differed from those activated by stimulation of the sensory pudendal or superficial perineal nerves, it is possible that specific pathways for different nerve inputs to the PAG exist. Sacral spinal cord neurons ascending to the PAG were identified by antidromic activation and then tested for inputs from pelvic, sensory pudendal or superficial perineal nerves. Of 18 units identified, only five received inputs from any of the peripheral nerves tested and only two projecting neurons received a pelvic nerve input. Thus the PAG may receive inputs from bladder and perineum, but the small proportion of cells with direct projections to the PAG receiving inputs from our test nerves implies that the major part of this pathway is not directly related to lower urinary tract function.     

Role of spinal alpha(1)-adrenergic mechanisms in the control of lower urinary tract in the rat

The role of spinal alpha(1)-adrenergic mechanisms in the control of urinary bladder function was examined in urethane (1.2 g/kg s.c.) anesthetized and decerebrate unanesthetized female Sprague-Dawley rats (250-320 g). Bladder activity was recorded via a transurethral catheter during continuous infusion (0.21 ml/min) cystometrograms or under isovolumetric conditions. All drugs were administered intrathecally at the L(6)-S(1) segmental level of spinal cord. During cystometrograms, 3 or 30 nmol of phenylephrine (alpha(1)-adrenergic agonist) did not alter bladder activity; whereas 300 nmol increased the intercontraction interval by 98% and pressure threshold for inducing micturition by 115%, but did not change bladder contraction amplitude. A large dose of phenylephrine (3000 nmol) completely blocked reflex voiding and induced overflow incontinence at a high baseline pressure (mean: 33 cmH(2)O; range: 28-42 cmH(2)O). Under isovolumetric conditions, 3-30 nmol of phenylephrine abolished bladder activity for 22-45 min; whereas smaller doses (0.003-0.3 nmol) were inactive. Doxazosin (50 nmol), an alpha(1)-adrenergic antagonist, decreased intercontraction intervals but did not change bladder contraction amplitude during cystometrograms. Under isovolumetric conditions this dose of doxazosin increased bladder contraction frequency and decreased bladder contraction amplitude. Smaller doses (5 or 25 nmol) of doxazosin did not alter bladder activity. These studies suggest that two types of spinal alpha(1)-adrenergic mechanisms are involved in reflex bladder activity: (1) inhibitory control of the frequency of voiding reflexes presumably by regulating afferent processing in the spinal cord and (2) facilitatory modulation of the descending limb of the micturition reflex pathway.     

Spinal cord representation of the micturition reflex

The spinal cord origin and peripheral pathways of the sensory and motor nerves to the urinary bladder were delineated in the cat by stimulating the appropriate nerves near the urinary bladder and recording from the dorsal and ventral rootlets near the spinal cord. The parasympathetic preganglionic neurons originated in the sacral segments of the spinal cord and reached the bladder by way of the pelvic nerve. The preganglionic parasympathetic perikarya to the urinary bladder were distributed over a length of approximately 1.5 segments, centered near the junction of segments S-2 and S-3 in cats with a median arrangement of the lumbosacral plexus. Conduction velocities in preganglionic parasympathetic fibers to the bladder ranged from 46 to 2 M/sec with a mean maximal velocity of 18.2 M/sec. The major sympathetic pathway to the bladder was in the hypogastric nerve. Preganglionic sympathetic fibers originated in the lumbar spinal cord and traveled through the caudal mesenteric ganglion and hypogastric nerve to the urinary bladder. There were both ipsilateral and contralateral preganglionic and afferent fibers in this pathway. The preganglionic sympathetic neurons originated in segments L-2 and L-5. They were usually distributed over approximately 2 full segments centered near the junction of L-3 and L-4 in cats with a median arrangement of the lumbosacral plexus. Neurons involved in the micturition reflex may extend from the rostral end of the L-2 segment to the caudal end of the S-3 segment. The sympathetic preganglionic neurons were usually separated from the somatic and parasympathetic columns by segments L-5 to L-7.     

Re-established micturition reflexes show differential activation patterns after lumbosacral ventral root avulsion injury and repair in rats

Previous studies have demonstrated that an acute implantation of lesioned lumbosacral ventral roots into the rat conus medullaris (CM) results in functional reinnervation of the lower urinary tract (LUT). Although the root implantation procedure results in a return of reflexive micturition, voiding efficiency (VE) remains incompletely recovered. Here, we performed a detailed urodynamic analysis of cystometry and external urethral sphincter (EUS) electromyography (EMG) recordings to determine underlying mechanisms for the incompletely recovered VE. For this purpose, adult female rats were studied at 12 weeks after a bilateral L5–S2 ventral root avulsion injury followed by an acute surgical implantation of the avulsed L6 and S1 ventral roots into the CM (n = 6). Age-matched sham-operated rats (n = 6) were included for control purposes. Compared to sham-operated controls, rats of the implanted series showed 1) reflex bladder contractions with a significantly shortened urine expulsion phase, 2) markedly decreased phasic EUS EMG activity during micturition, and 3) a pronounced bladder–sphincter dys-coordination, as demonstrated by a significantly delayed onset of the switch from low-amplitude tonic EUS EMG activity to either phasic EUS EMG activity or a large-amplitude tonic EUS EMG activity during the urine expulsion phase. Our findings provide a mechanistic explanation for the incomplete recovery of the VE following implantation of avulsed ventral roots into the spinal cord. Our future studies will aim to increase successful axonal regeneration in attempts to augment the recovery of the LUT after cauda equina injury and repair.     

Bladder and urethral sphincter responses evoked by microstimulation of S2 sacral spinal cord in spinal cord intact and chronic spinal cord injured cats

Urinary bladder and urethral sphincter responses evoked by bladder distention, ventral root stimulation, or microstimulation of S2 segment of the sacral spinal cord were investigated under alpha-chloralose anesthesia in cats with an intact spinal cord and in chronic spinal cord injured (SCI) cats 6-8 weeks after spinal cord transection at T9-T10 spinal segment. Both SCI and normal cats exhibited large amplitude reflex bladder contractions when the bladder was fully distended. SCI cats also exhibited hyperreflexic bladder contractions during filling and detrusor-sphincter dyssynergia during voiding, neither was observed in normal cats. Electrical stimulation of the ventral roots revealed that the S2 sacral spinal cord was the most effective segment for evoking large amplitude bladder contractions or voiding in both types of cats. Microstimulation with a stimulus intensity of 100 microA and duration of 30-60 s via a single microelectrode in the S2 lateral ventral horn or ventral funiculus evoked large amplitude bladder contractions with small urethral contractions in both normal and SCI cats. However, this stimulation evoked incomplete voiding due to either co-activation of the urethral sphincter or detrusor-sphincter dyssynergia. Stimulation in the S2 dorsal horn evoked large amplitude sphincter responses. The effectiveness of spinal cord microstimulation with a single electrode to induce prominent bladder and urethral sphincter responses in SCI animals demonstrates the potential for using microstimulation techniques to modulate lower urinary tract function in patients with neurogenic voiding dysfunctions.     

Serotonergic modulation of spinal ascending activity and sacral reflex activity evoked by pelvic nerve stimulation in cats

Serotonin (5-HT) may be inhibitory to micturition at a spinal level. A potential mechanism of action for serotonergic inhibition of bladder function is a depression of the ascending limb of the supraspinal reflex mediating micturition. Ascending activity evoked by pelvic nerve stimulation was recorded in the thoracic spinal cord of anesthetized cats. For comparison, spinal reflex activity evoked by pelvic nerve stimulation was recorded on the pudendal nerve. The effects of intrathecal administration of serotonergic agents were examined to determine whether spinal and supraspinal responses to bladder afferent activation were modulated by 5-HT. Methysergide (60 nmol), a non-selective serotonergic antagonist, increased ascending activity by 61±7% and depressed spinal reflex activity by 38±6%. Zatosetron (10 nmol), a 5-HT₃ antagonist had a similar effect on both activities (increased by 93±24% and decreased by 77±7%, respectively). The effect on ascending activity of blocking 5-HT₃ receptors was also confirmed with ICS 205930 and MDL 72222. 2-Methyl-5-HT (800 nmol), a 5-HT₃ agonist, depressed ascending activity to 46±9% of control, but enhanced spinal reflex activity by 73±92%. These results demonstrate that stimulation of 5-HT₃ and methysergide-sensitive 5-HT receptors can inhibit ascending activity and facilitate spinal reflex activity elicited by activation of bladder afferents. It is suggested that descending serotonergic pathways may participate in the spinal coordination of urinary continence.     

Changes in galanin immunoreactivity in rat lumbosacral spinal cord and dorsal root ganglia after spinal cord injury

Alterations in the expression of the neuropeptide galanin were examined in micturition reflex pathways 6 weeks after complete spinal cord transection (T8). In control animals, galanin expression was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure; (2) the superficial dorsal horn; (3) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (L6-S1); and (4) the lateral collateral pathway in lumbosacral spinal segments. Densitometry analysis demonstrated significant increases (P < or = 0.001) in galanin immunoreactivity (IR) in these regions of the S1 spinal cord after spinal cord injury (SCI). Changes in galanin-IR were not observed at the L4-L6 segments except for an increase in galanin-IR in the dorsal commissure in the L4 segment. In contrast, decreases in galanin-IR were observed in the L1 segment. The number of galanin-IR cells increased (P < or = 0.001) in the L1 and S1 dorsal root ganglia (DRG) after SCI. In all DRG examined (L1, L2, L6, and S1), the percentage of bladder afferent cells expressing galanin-IR significantly increased (4-19-fold) after chronic SCI. In contrast, galanin expression in nerve fibers in the urinary bladder detrusor and urothelium was decreased or eliminated after SCI. Expression of the neurotrophic factors nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) was altered in the spinal cord after SCI. A significant increase in BDNF expression was present in spinal cord segments after SCI. In contrast, NGF expression was only increased in the spinal segments adjacent and rostral to the transection site (T7-T8), whereas spinal segments (T13-L1; L6-S1), distal to the transection site exhibited decreased NGF expression. Changes in galanin expression in micturition pathways after SCI may be mediated by changing neurotrophic factor expression, particularly BDNF. These changes may contribute to urinary bladder dysfunction after SCI.