Lower urinary tract function in spinal cord-injured rats: Midthoracic contusion versus transection

Abstract

Objectives:
To compare changes in lower urinary tract (LUT) function with modifications in pathways that regulate LUT function using two different animal models (incomplete and complete) of spinal cord injury (SCI).

Methods:
Female Sprague-Dawley rats were used. SCI was made at Th8/9 by a contusion injury (contusion, n=9) or a complete transection (transection, n=9). Unoperated rats were used as normal controls (normal, n=6). LUT function was evaluated by micturition behavior in metabolic cages for 24 h and cystometry in awake animals. Immunocytochemical staining at the L6 spinal cord, spinal areas associated with LUT, was performed to identify descending modulatory fibers and dorsal root afferents that project to the L6 spinal cord.

Results:
Volume/micturition in metabolic cages gradually increased in both contusion and transection groups compared with normals, and operated groups did not differ from each other. Urodynamic parameters from cystometry were significantly different in contusion and transection groups compared with normals, but again there was no significant difference between contusion and transection groups. Immunocytochemical analyses at the L6 spinal cord showed no serotonergic or noradrenergic fibers in transection group, but some descending fibers remained in contusion group, indicating sparing. Small dorsal root afferents were denser in both contusion and transection groups than in normals, indicating sprouting.

Conclusions:
Although differences were not found in LUT function in operated animals, supraspinal and dorsal root projections to the L6 spinal cord responded differently to contusion and transection. This suggests that the benefits of pharmacologic treatments may be different in two lesion models.

Full text

ORIGINAL ARTICLE
Lower urinary tract function in spinal cord-injured rats:
midthoracic contusion versus transection
T Mitsui1,2,MMurray
2and K Nonomura1
Objectives: To compare changes in lower urinary tract (LUT) function with modifications in pathways that regulate LUT function using
two different animal models (incomplete and complete) of spinal cord injury (SCI).
Methods: Female Sprague–Dawley rats were used. SCI was made at Th8/9 by a contusion injury (contusion, n¼9) or a complete
transection (transection, n¼9). Unoperated rats were used as normal controls (normal, n¼6). LUT function was evaluated by
micturition behavior in metabolic cages for 24 h and cystometry in awake animals. Immunocytochemical staining at the L6 spinal
cord, spinal areas associated with LUT, was performed to identify descending modulatory fibers and dorsal root afferents that project
to the L6 spinal cord.
Results: Volume/micturition in metabolic cages gradually increased in both contusion and transection groups compared with
normals, and operated groups did not differ from each other. Urodynamic parameters from cystometry were significantly different in
contusion and transection groups compared with normals, but again there was no significant difference between contusion and
transection groups. Immunocytochemical analyses at the L6 spinal cord showed no serotonergic or noradrenergic fibers in transection
group, but some descending fibers remained in contusion group, indicating sparing. Small dorsal root afferents were denser in both
contusion and transection groups than in normals, indicating sprouting.
Conclusions: Although differences were not found in LUT function in operated animals, supraspinal and dorsal root projections to the
L6 spinal cord responded differently to contusion and transection. This suggests that the benefits of pharmacologic treatments may be
different in two lesion models.
Spinal Cord (2014) 52, 658–661; doi:10.1038/sc.2014.114; published online 15 July 2014
INTRODUCTION
Spinal cord injury (SCI) is classified clinically into complete injuries,
where function below the level of a injury is lost, and incomplete
injuries where some sensory and/or motor function is retained.
Nevertheless, it is known that some descending pathways are spared
in many cases of clinically complete injuries.1
Lower urinary tract (LUT) dysfunction in SCI results from damage
to descending modulatory pathways and increased sensory input
through sprouting of primary afferent pathways. A contusion injury
that we use destroys the dorsal spinal cord in the thoracic region,
including the dorsal columns, the corticospinal tract and the
dorsolateral (DL) funiculus, damages the dorsal horn (DH) and
impinges on the intermediolateral column.2–4 Thus, the ventral
funiculi and the ventral portions of the lateral funiculi, which
contain descending modulatory pathways, were partially spared in
contusion injuries, but not in transection injuries.
Serotonergic axons project to the DL nucleus in the spinal cord,
which has been implicated in the central control of the bladder and
the urethra and recovery of bladder-external urethral sphincter
coordination in SCI rats.5,6 Brainstem-spinal noradrenergic axons
project to the lumbosacral spinal cord including the sacral
parasympathetic nucleus (SPN) whose axons innervate the LUT.5,7
In SCI, disruption of these modulatory descending pathways induces
sprouting of the small-diameter dorsal root afferents, for example,
calcitonin gene-related peptide (CGRP)-positive fibers3in the DH. If
the descending fibers are partially preserved even in a clinically
compete injury of the spinal cord, they could offer targets for LUT
treatment even after severe SCI. However, because most animal
studies of LUT function have used a transection model, which is
both anatomically and clinically complete spinalized animals, they
may not model the clinically complete cases of LUT dysfunction in
which some projections may be spared.
In our previous studies,2–4 we have shown that a cellular graft
placed into a contusion injury site, such as we use in this study,
improved LUT function and was associated with changes in pathways,
presumably due to the neuroprotective effects of the grafts. We also
showed that intrathecal administration of adrenergic antagonists
further improved function,3likely by acting on spared and/or
sprouting noradrenergic pathways. Here, we compared LUT
function with changes in descending modulatory and primary
afferent projections after a complete transection with a clinically
relevant model, a contusion injury, in the absence of invasive
procedures such as grafting or pharmacological treatment.
MATERIALS AND METHODS
Animal groups
Twenty-four 10-week-old Sprague–Dawley rats (225–250 g; Taconic, German-
town, MA, USA) were used. Nine rats received a contusion injury of the spinal
1Department of Urology, Hokkaido University Graduate School of Medicine, Sapporo, Japan and 2Department of Neurobiology and Anatomy, Drexel University College of Medicine,
Philadelphia, PA, USA
Correspondence: Dr T Mitsui, Department of Urology, Hokkaido University Graduate School of Medicine, North-15, West-7, Kita-ku, Sapporo 060-8638, Japan.
E-mail: mitsui68@med.hokudai.ac.jp
Received 7 February 2014; revised 23 May 2014; accepted 6 June 2014; published online 15 July 2014
Spinal Cord (2014) 52, 658–661
&
2014 International Spinal Cord Society All rights reserved 1362-4393/14
www.nature.com/sc

cord (contusion). Nine rats received a complete transection of the spinal cord
(transection, n¼9). Unoperated rats were used as normal controls (normal,
n¼6).
Rats had free access to food and water and were kept under a 12-h light/dark
cycle. All procedures were approved by the Drexel University College of
Medicine’s Institutional Animal Care and Use Committee and conformed to
the National Institute of Health guidelines for the care and use of laboratory
animals.
SCI procedures
Animals were anesthetized with intraperitoneal injection of XAK cocktail
containing xylazine (10 mg kg1), acepromazine maleate (0.7 mg kg 1)and
ketamine (95 mg kg1), and a laminectomy was performed at T8/9. In a
contusion model, a modified moderate contusion injury was created using the
impact rod of the MASCIS device dropped from a height of 25 mm and
allowed to rest on the spinal cord for 5 s.2,3 In a complete transection model,
the spinal cord was cut with microscissors at T8/9 as previously described.8
Muscle and skin were closed in layers after SCI.
Rats were placed on heating pads, and closely observed until awake before
returning them to their home cage. Bladders were manually expressed twice
daily until killing, except during testing in metabolic cages.
Micturition pattern
Rats with SCI were placed in metabolic cages (Nalgene Metabolic Cage, Nalge
Co., Rochester, NY, USA) for 24 h to measure micturition behavior preopera-
tively and at weekly intervals from week 2 to week 9 after SCI. The bladders
were expressed manually before the animals were placed in the metabolic cage.
The urine voided during the next 24h was collected on an electronic scale
(FORT250, World Precision Instruments, Sarasota, FL, USA), connected to a
microcomputer, for recording micturition frequency and volume.2,3 Data were
recorded and stored using data acquisition software (WINDAQ, DATAQ
Instruments, Akron, OH, USA). The voided volume per micturition was
compared between experimental groups.
Cystometry in conscious rats
At week 9 post injury, rats were anesthetized using isoflurane inhalation and
the bladder exposed by a midline lower abdominal incision. A polyethylene
catheter (PE-60, Clay-Adams, Parsippany, NJ, USA) was implanted into the
bladder through the dome, as described previously.2,3 The catheter was
tunneled subcutaneously and exited through the skin on the back.
Following catheter implantation, rats were placed in a restraining cage
(KN-326, Natsume, Tokyo, Japan) and allowed to recover from the anesthesia
for 1–2h. The bladder catheter was connected to a pressure transducer (BLPR,
World Precision Instruments) and a microinjection pump (STC-523, Terumo,
Tokyo, Japan). Room-temperature saline was infused at a rate of 0.1 ml min1.
Micturition cycles stabilized and became regular after about 30min of saline
infusion. Three micturition cycles were collected after stabilization. The
averages of maximal voiding pressure, post-void residual urine, bladder
capacity and the frequency of non-voiding contraction in these micturition
cycles were compared among groups. Fluid voided from the urethral meatus
was collected to determine the voided volume. Residual fluid was first
withdrawn through the catheter and then the bladder was expressed manually
by applying pressure on the abdominal wall to collect the remaining
intravesical contents. Bladder capacity was calculated as the voided volume
plus residual volume. Non-voiding contraction was defined as rhythmic
intravesical pressure increases greater than 5mmHg from baseline without a
release of fluid from urethra.2,3
Tissue preparation
After cystometry, animals were anesthetized with intraperitoneal injections of
sodium pentobarbital (100 mg kg 1, Abbot Laboratories, North Chicago, IL,
USA) and killed by intracardiac perfusion with 200 ml of 0.1 M,pH7.4,
phosphate buffer followed by 500 ml of ice-cold 4% paraformaldehyde fixative
in phosphate buffer. The spinal cord was removed and postfixed for 24h in the
same fixative at 4 1C followed by cryoprotection in phosphate-buffered 30%
sucrose solution for 3–5 days. Tissues were serially blocked, embedded in
Optimal Cutting Temperature compound (Fisher Scientific, Pittsburgh, PA,
USA) and kept at 80 1C before being cut into 30 mm coronal sections at the
L6 level.
Lesion sections were evaluated for completeness of the injury in transection
group or the extent of sparing of descending pathways in contusion group.
Transections of the spinal cord were complete and contusion injuries were
similar to those described previously.2–4,8
Projection patterns at the L6 spinal cord
Coronal sections at the L6 level were immersed in 0.1 M, pH 7.6, phosphate-
buffered saline for free floating staining using the avidin–biotin complex
method. Sections were permeabilized with 10% goat serum in phosphate-
buffered saline for 2 h, then incubated with the appropriate primary antibody
(serotonin (5-hydroxytryptamine; 1:50000, ImmunoStar Inc., Hudson, WI,
USA), dopamine-beta-hydroxylase (DbH; 1:1000, Protos Biotech Corporation,
New York, NY, USA) for noradrenergic fibers, CGRP for small diameter
primary afferents (1:6000, Peninsula Laboratories Inc., San Carlos, CA, USA))
and 2% goat serum in phosphate-buffered saline containing 0.3% Triton X-100
at 4 1C for 24–48 h, and finally reacted with a species-specific biotinylated
secondary antibody and the ABC reagent (Vector, Burlingame, CA, USA), each
for 2 h at room temperature. Staining was visualized with Sigma fast DAB
(Sigma Chemicals, Perth, WA, Australia). Tissue sections were mounted on
gelatin-coated slides, dehydrated in graded ethanol, cleaned in xylene and
coverslipped. All sections were examined using bright-field microscopy and
images were analyzed using NIH Image.2–4
Statistical analysis
Cystometric data and density of immunocytochemically positive-fibers were
analyzed using one-way analysis of variance between groups. Voided volume
per micturition in metabolic cage was analyzed using two-way analysis of
variance between group and time, with time as a repeated measure beginning
at 2 weeks post injury. Post -hoc analysis was performed using Fisher’s post-hoc
test. Data are presented as group mean±standard error. Significance levels
were set to 0.05 for all comparisons.
RESULTS
LUT function
Micturition behavior in metabolic cage. Voided volume/micturition
gradually increased, indicating recovery from spinal shock. Although
an increase of voided volume/micturition seemed to be slightly earlier
in contusion group, there was no statistically significant difference
between contusion and transection groups (Figure 1).
Cystometry. Urodynamic parameters from cystometry, including
micturition pressure, non-voiding contraction, bladder capacity and
post-void residual urine volume, were markedly increased in both
Micturition Behavior
(ml)
2
1.5
1
Voided volume / Micturition
0.5
Contusion Transection
0
Baseline 2w 3w 4w 5w 6w 7w 8w 9w
Figure 1 Micturition following contusion or transection of the spinal cord.
Voided volume/micturition was gradually increased in both contusion and
transection models, indicating recovery from spinal shock. w, week.
LUT function in SCI rats
TMitsuiet al
659
Spinal Cord

contusion and transection groups compared with normals (wPo0.05,
normal vs contusion, zPo0.05, normal vs transection). There was no
significant difference between contusion and transection groups in
these parameters (Table 1).
Anatomical changes
Projection patterns of modulatory descending projections at the L6 spinal
cord. At the L6 level in normal group, serotonin-positive fibers were
observed in the DL nucleus and the DH, DbH-positive labeled fibers,
indicating noradrenergic axons, were identified in the DL nucleus and
the SPN. Some serotonin- (Figure 2) and DbH- (Figure 3) positive
fibers were identified in contusion group, indicating sparing of some
descending fibers (arrows). As expected, no such labeling was seen in
transection group, indicating no other sources for these descending
modulators in the spinal cord.
Primary afferent projections at the L6 spinal cord. In normal group,
CGRP-positive fibers project to the superficial layers of the DH.
Following injury, CGRP immunoactivity was modestly denser in
both contusion and transection groups compared with normals
(Figure 4a), and some entopic fibers extended into the deeper layers
of the DH. Densitometric analyses showed that CGRP immunor-
eactivity in the DH was significantly denser in contusion and
transection groups than in normals (transection vs normal:
Po0.05, contusion vs normal: Po0.05), but there was no significant
difference between transection and contusion groups (Figure 4b).
These results suggest increased sprouting of small caliber dorsal root
axons to the DH in both the transection and contusion groups
compared to normals.
DISCUSSION
In animal models, SCI produces an initial period of bladder areflexia,
followed by the slow re-emergence of involuntary reflex micturition
and detrusor hyperactivity mediated by spinal reflex pathways.
Coordinated function between the bladder and urethral sphincter is
disrupted after SCI, and the degree of dyssynergia is related to
the severity of spinal injury.6This loss of coordination leads to
functional bladder outlet obstruction identified by urinary retention
and increased micturition pressure. Non-voiding contractions,
manifested as phasic bladder contractions during urine storage,
result in urinary incontinence and high intravesical pressures,
leading to bladder hypertrophy and deterioration of the upper
urinary tract. Non-voiding contractions are likely to reflect
hyperactivity of the primary afferent projection. In the present
study, the lack of significant differences in LUT function in
micturition behavior or cystometry indicates that the injuries were
functionally equivalent between contusion and transection.
Table 1 Summary of urodynamic parameters in cystometry
Parameters Normal Contusion Transection
Micturition pressure (cm water) 19.5±0.8 36.1±2.9a33.3±1.5b
Number of non-voiding contraction
(/micturition)
07.0
±1.1a5.9±1.1b
Bladder capacity (ml) 0.44±0.05 1.54±0.07a1.53±0.14b
Post-void residual urine volume (ml) 0.03±0.01 0.16±0.04a0.20±0.06b
aPo0.05, normal vs contusion.
bPo0.05, normal vs transection.
Serotonin-positive fibers
Normal Contusion Transection
Dorsolateral nucleus
Dorsal horn
Figure 2 5-HT-positive fibers in the lumbosacral spinal cord. Some
serotonin-positive fibers identified in contusion group, although the density
of serotonin-positive fibers was low compared with unoperated rats. There
were no fibers of these descending pathways in transection group. Arrows in
contusion: serotonin-positive fibers.
Normal Contusion Transection
Dorsolateral
nucleus
sacral
nucleus
parasympathetic
D H-positive fibers
Figure 3 DbH-positive fibers in the lumbosacral spinal cord. Some
DbH-positive fibers identified in contusion group, but none in transection
group. Arrows in contusion: DbH-positive fibers
Dorsal horn
50
(%)
30
40 **
10
20
0
Normal Contusion Transection
Normal Contusion Transection
Figure 4 CGRP-positive fibers in the lumbosacral spinal cord. CGRP-positive
fibers were modestly denser in the superficial dorsal horn and some entopic
fibers were seen in deeper layers in both contusion and transection groups
compared with unoperated normal rats (a). CGRP immunoreactivity in the
DH was significantly denser in transection and contusion groups than in
normal rats (b). *Po0.05.
LUT function in SCI rats
TMitsuiet al
660
Spinal Cord

However, differences in extent of innervation of the lumbar spinal
cord by the serotonergic and noradrenergic axons and in the density
of CGRP-labeled dorsal root projections to the DH were observed
between operated groups. The L6 spinal cord contains preganglionic
parasympathetic neurons in the SPN that innervate the ganglia
supplying the smooth muscle of the bladder wall,5and the DL
nucleus, which contains somatic motor neurons that innervate the
external urethral sphincter and coordinate the activity of the bladder
and the urethra.5,6 Our previous studies suggested that the greater
density of descending serotonergic and noradrenergic projections,
elicited by the neuroprotective effects of the cellular grafts
transplanted into a contusion lesion site, ameliorates of the
dyssynergia between the bladder and the urethral sphincter2–4 by
providing some descending control over spinal nuclei and greater
descending control over sensory transmission in the DH.9–12 The
density of bladder afferent projections, that is, CGRP-positive fibers in
the DH, is increased after severe SCI13–15 and this has been implicated
in detrusor overactivity that develops following SCI.2–4 Bladder
afferents in the lumbosacral spinal cord also project to the DH,
SPN and dorsal commissure in the lumbosacral spinal cord,16,17
which was induced by disruption of the descending projections.
These findings provide greater descending control over sensory
transmission in the DH.9–12
Some serotonin- and DbH-positive fibers were preserved in
contusion group at the L6 spinal cord, but none were present in
transection group. CGRP-positive fibers were denser in both contu-
sion and transection groups than in normals. The discrepancy
between similar urodynamic parameters in metabolic cages and in
cystometry and differences in projection patterns is not uncommon.
A likely explanation is that the sparing of descending projections was
insufficient to permit measurable recovery. In fact, LUT function
spontaneously recovers following a mild contusion injury of the
spinal cord and more severe contusion injury induces permanent LUT
dysfunction.6Our previous study showing that transplantation of
cellular grafts after similar contusion lesions improved LUT function
compared with SCI animals without treatments. This was attributed
to the greater sparing of descending modulatory pathways because
of the neuroprotective properties of the transplanted cells and
indeed was demonstrated immunocytochemically. We show here
that sprouting/sparing occurs even without a graft but is less
pronounced, and is not associated with recovery of LUT function.
In LUT dysfunction after SCI, effects of administration of agonists
or antagonists may differ according to the injury type. The appro-
priate medication is likely to differ between contusion and transection
groups, as a low density of serotonin- and DbH-positive fibers was
preserved in the spinal cord of contusion group. Our previous studies
suggest that a difference in response to a contusion injury treated
with a cellular graft into the lesion site, compared with a contusion
injury without a cellular graft, showed a greater response to alpha
1-adrenergic blockers in urodynamic parameters.3,18 This indicated
that there was possibility of different sensitivity for alpha 1-adrenergic
receptor subtypes. We suggest that there will be different
pharmacological responses with serotonergic agents between
contusion and transection groups as well.19 Further, alterations in
NMDA receptors involved in recovery of urethral sphincter
coordination6suggest a potential clinical application using
glutaminergic agonists.1,20 Thus, if pharmacological data from
animal studies are applied to clinical treatments, the preclinical
studies should be done in both contusion and transection injuries.
In conclusion, although a significant difference was not found in
LUT function, supraspinal projections to the lumbosacral spinal cord
were significantly different between contusion and transection groups.
This suggests that anatomical plasticity occurs following both
complete and incomplete injuries and that the benefits of pharma-
cologic treatments may be different in two lesion models.
DATA ARCHIVING
There were no data to deposit.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
ACKNOWLEDGEMENTS
This study was supported by Spinal Cord Research Foundation (No. 2312-01)
and Uehara Memorial Foundation.
1 Angeli CA, Edgerton VR, Gerasimenko YP, Harkema SJ. Altering spinal cord excitability
enables voluntary m ovements after chronic complete paralys is in humans. Brain 2014;
137: 1394.
2 Mitsui T, Neuhuber B, Fischer I. Acute administration of AMPA/Kainate blocker
combined with delayed transplantation of neural precursors improves lower urinary
tract function in s pinal injured rats. Brain Res 2011; 1418:23.
3 Mitsui T, Shumsky JS, Lepore AC, Murray M, Fischer I. Transplantation of neuronal and
glial restricted precursors into contused spinal cord improves bladder and motor
functions, decreases thermal hypersensitivity, and modifies intraspinal circuitry.
JNeurosci2005; 25: 9624.
4 Mitsui T, Fischer I, Shumsky JS, Murray M. Transplants of fibroblasts expressing BDNF
and NT-3 promote recovery of bladder and hindlimb function following spinal contusion
injury in rats. Exp Neurol 2005; 194:410.
5 Marson L. Identification of central nervous system neurons that innervate the bladder
body, bladder base, or external urethral sphincter of female rats: a transneuronal
tracing study using p seudorabies virus. JCompNeurol1997; 389:584.
6 Pikov V, Wrathall JR. Coordination of the bladder detrusor and the external urethral
sphincter in a rat model of spinal cord injury: effect of injury severity. JNeurosci2001;
21:559.
7 Westlund KN, Bowker RM, Ziegler MG, Coulter JD. Noradrenergic projections to the
spinal cord of the rat. Brain Res 1983; 263:15.
8 Nothias JM, Mitsui T, Shumsky JS, Fischer I, Antonacci MD, Murray M. Combined
effects of neurotrophin secreting transplants, exercise, and serotonergic drug challenge
improve function in spinal rats. Neurorehabil Neural Repair 2005; 19:296.
9 Millan MJ. Descending control of pain. Prog Neurobiol 2002; 66:355.
10 Tsuruoka M, Maeda M, Nagasawa I, Inoue T. Spinal pathways mediating coeruleospinal
antinociception in the rat. Neurosci Lett 2004; 362:236.
11 Ueyama T, Arakawa H, Mizuno N. Central distribution of efferent and afferent
components of the p udendal nerve in rat. Anat Embryol (Berl) 1987; 177:37–49.
12 Suzuki R, Morcuende S, Webber M, Hunt SP, Dickenson AH. Superficial
NK1-expressing neurons control spinal excitability through activation of descending
pathways. Nat Neurosci 2002; 5: 1319.
13 Krenz NR, Meakin SO, Krassioukov AV, Weaver LC. Neutralizing intraspinal nerve
growth factor b locks autonomic dysreflexia c aused by spinal cord injury. JNeurosci
1999; 19: 7405.
14 Zhou Y, Wang Y, Abdelhady M, Mourad MS, Hassouna MM. Change of vanilloid receptor
1 following neuromodulation in rats with spinal cord injury. JSurg Res2002; 107:
140.
15 Hains BC, Willis WD, Hulsebosch CE. Temporal plasticity of dorsal horn somatosensory
neurons after acute and chronic spinal cord hemisection in rat. Brain Res 2003; 970:
238.
16 Jancso G, Maggi CA. Distribution of capsaicin-sensitive urinary bladder afferents in the
rat spinal cord. Brain Res 1987; 418:371.
17 Steers WD, Ciambotti J, Etzel B, Erdman S, de Groat WC. Alterations in afferent
pathways from the urinary bladder of the rat in response to partial urethral obstruction.
JCompNeurol1991; 310:401.
18 Miyazato M, Oshiro T, Chancellor MB, de Groat WC, Yoshimura N, Saito S. An alpha1-
adrenoceptor blocker terazosin improves urine storage function in the spinal cord in
spinal cord injured rats. Life Sciences 2013; 92:125.
19 Chang HH, Havton LA. Serotonergic 5-HT(1?A) receptor agonist (8-OH-DPAT) amelio-
rates impaired micturition reflexes in a chronic ventral root avulsion model of
incomplete cauda equina/conus medullaris injury. Exp Neurol 2013; 239:210.
20 Liao JM, Yang CH, Cheng CL, Pan SF, Chen MJ, Huang PC et al. Spinal glutamatergic
NMDA-dependent cyclic pelvic nerve-to-external urethra sphincter reflex potentiation
in anesthetized rats. American journal of physiology. Renal Physiol 2007; 293:F790.
LUT function in SCI rats
TMitsuiet al
661
Spinal Cord