Sham Surgery Rats Research Articles

A Rat Model for Intracranial Facial Nerve Crush Injuries

(1) Explain the need for an animal model to study intracranial injuries to the facial nerve. (2) Describe various techniques attempted to identify and crush the intracranial segment of the facial nerve in a rat model. (3) Describe in detail a successful rat model of intracranial facial nerve crush injury. Randomized controlled animal study. Animal laboratory. Multiple attempts at surgical approaches to the cerebellopontine angle were attempted on cadaveric rats. Once a successful approach was derived, this was used on 19 live rats under anesthesia. Fourteen rats had a 1-minute facial nerve crush performed, and 5 had a sham surgery with complete surgical exposure of the facial nerve but no crush. Rats were followed for a 12-week duration evaluating immediate postoperative facial nerve function, complications, and survival. All 14 (100%) rats that underwent surgery with crush injury had complete facial paralysis postoperatively. Complete facial paralysis was defined as loss of eye-blink reflex, flat vibrissae, and lack of vibrissae movement. The 5 sham surgery rats had complete facial function postoperatively. Surgery was performed by 2 separate surgeons with no difference in outcome between the 2. Complications occurred in only 1 animal (1/19, 5.3%), which was a corneal abrasion requiring sacrifice. Our group describes a consistent method for performing an intracranial crush injury in the rat. This new model and its applications in translational facial nerve research are promising, particularly with tumors or lesions at the cerebellopontine angle.

Voluntary physical activity and leucine correct impairments in muscle protein synthesis in partially pancreatectomised rats

Poorly controlled type 1 diabetes mellitus can cause reduced skeletal muscle mass and weakness during adolescence, which may affect long-term management of the disease. The aim of this study was to determine whether regular voluntary physical activity and leucine feeding restore rates of protein synthesis and deficits in skeletal muscle mass in a young, hypoinsulinaemic/hyperglycaemic rat model of diabetes. Four-week-old male Sprague-Dawley rats were partially pancreatectomised (Px) to induce hypoinsulinaemia/hyperglycaemia and housed with/without access to running wheels for 3 weeks (n = 12-14/group). Sham surgery rats (shams) served as sedentary controls (n = 18). Protein synthesis and markers of protein anabolism were assessed in the fasted state and following leucine gavage. Fibre type and cross-sectional areas of the gastrocnemius muscle were measured using a metachromatic ATPase stain. Compared with sedentary behaviour, regular activity lowered fasting glycaemia and reduced fed hyperglycaemia in Px rats. Active-Px rats, which ran 2.2 ± 0.71 km/night, displayed greater muscle mass and fibre areas similar to shams, while sedentary-Px rats displayed a 20-30% loss in muscle fibre areas. Muscle protein synthesis (basal and in response to leucine gavage) was impaired in sedentary-Px (by ~65%), but not in active-Px rats, when compared with shams. Following leucine gavage, the phosphorylation status of eIF4E binding protein 1 (4E-BP1) and ribosomal S6 kinase 1 (S6K1), markers of mammalian target of rapamycin complex 1 (mTORC1) signalling, increased in shams (by two- and ninefold, respectively) and in active-Px (1.5- and fourfold, respectively) rats, but not in sedentary-Px rats. Moderate physical activity in young Px rats normalises impairments in skeletal muscle growth and protein synthesis. These findings illustrate the critical compensatory role that modest physical activity and targeted nutrition can have on skeletal muscle growth during periods of hypoinsulinaemia in adolescent diabetes.

An Autoradiographic Study on the Pathogenesis of Levodopa-Induced Dyskinesia: Regulation of Dopamine Transporter by Levodopa in a Rat Model of Parkinson’s Disease

Background: The development of abnormal involuntary movements or dyskinesia is a serious complication of L-3,4-dihydroxyphenylalanine (L-DOPA) therapy for Parkinson’s disease (PD). Objective: To evaluate the correlation between dopamine transporter (DAT) regulated by L-DOPA and the pathogenesis of dyskinesia in PD rats. Methods: Thirty rats were used to establish the PD model by injecting 6-hydroxydopamine into the right medial forebrain bundle. The sham surgery rats (n = 4) received 4 µl of physiological saline. Then, 19 rats in which PD has been successfully induced were randomly assigned to the L-DOPA (20 mg/kg/day; n = 15) or model (saline; n = 4) group. After 4 weeks of treatment, ¹³¹I-N-(3-fluoropropyl)-2β-carbomethoxy-3 β-(4-iodophenyl)nortropane was injected into the rats, and images of DAT in the brain were acquired using a storage phosphor plate. The levels of DAT-specific radioactivity uptake in the bilateral corpora striata (left/right) were compared. Results: There was no difference in DAT-specific radioactivity uptake between the bilateral corpora striata in the sham surgery rats. The images were clear and symmetrically distributed in the corpora striata. In PD model rats, the DAT-specific radioactivity uptake decreased on the lesioned side and the ratios of uptake between the corpora striata were increased. Accumulation of the radioligand on the lesioned side was sparse. In the L-DOPA group, the average ratio values were significantly increased in dyskinetic rats and reduced in nondyskinetic rats. In addition, the differences between the bilateral corpora striata were reduced in nondyskinetic rats. Conclusion: L-DOPA was shown to downregulate DAT in some PD model rats. That process may be involved in the pathogenesis of dyskinesia.

Function and expression pattern of TRPM8 in bladder afferent neurons associated with bladder outlet obstruction in rats

We investigated the function and expression pattern of the transient receptor potential melastatin-8 (TRPM8) in urinary bladder afferent neurons from control and bladder outlet obstruction (BOO) rats. BOO was produced and, after six weeks, the effects of intravesical infusion of menthol, the agonist of TRPM8, were investigated using unanesthetized cystometry. The intravesical infusion of menthol produced an increase in the micturition pressure in both sham surgery and BOO rats. In BOO rats, increased basal and threshold pressure and a decreased micturition interval were observed. Next, the population of TRPM8-positive and the co-expression proportion of TRPM8 with neurochemical markers (NF200 or TRPV1) in the bladder afferent neurons were each compared between the control and BOO rats using retrograde tracing and immunohistochemistry. The population of TRPM8-immunoreactive bladder afferent neurons was larger in BOO rats (3.28±0.43%) than in the control rats (1.33±0.18%). However, there were no statistical differences between the control and BOO rats in the co-expression proportion of neither TRPM8-NF200 (84.1±4.3% vs 79.7±2.7%, p=0.41) nor TRPM8-TRPV1 (33.3±3.6% vs 40.8±2.6%, p=0.08) in the bladder afferent neurons. The present results suggest that the neuronal input through TRPM8-positive bladder afferent neurons are augmented after BOO, however, the neurochemical phenotype of the up-regulated TRPM8-positive bladder afferent neurons is not changed after BOO.

Novel rat model of stress urinary incontinence with a retroflexed bladder

We created a rat model with a retroflexed bladder that mimicked the loss of the posterior urethrovesical angle and compared the results with sham-surgery rats for the establishment of rat models of stress urinary incontinence. The retroflexed bladder was created by stitching the bladder posteriorly to the psoas muscle. Sneeze-induced urethral pressure response and urethral baseline pressure were measured using a microtip-transducer catheter and leak point pressures induced by sneezing, the Crede maneuver, and the vertical tilt table method were measured via a supra-pubic cystostomy. In rats with a retroflexed bladder, both urethral pressure response and sneeze-induced leak point pressure were significantly decreased. A retroflexed bladder may cause stress urinary incontinence by attenuating the sneeze-induced active urethral closure mechanism. Urethral pressure response restored by resumption of the posterior urethrovesical angle would explain why no sling tension is needed to treat the stress urinary incontinence.

Dietary n-3 polyunsaturated fatty acids increase oxidative stress in rats with intracerebral hemorrhagic stroke

Intake of n-3 polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has been suggested to associate with an increased risk of hemorrhagic stroke. The present study was designed to investigate the hypothesis that EPA and DHA increase oxidative stress and hemorrhage volume in rats with intracerebral hemorrhagic (ICH) stroke. Thirty-five-week-old male rats were fed an American Institute of Nutrition-93M diet containing 0% (n = 27), 0.5% (n = 15), or 1% EPA + DHA of total energy for 5 weeks. Of 5 rats fed 1% EPA + DHA (41%), 5 died because of excessive bleeding within 12 hours after ICH surgery. Behavior test score and hemorrhage volume were significantly (P < .05) greater in the 1% EPA + DHA-fed rats than in other rats. Magnetic resonance imaging consistently showed that edema and bleeding were visible in only the rats fed 1% EPA + DHA. Levels of superoxide dismutase and glutathione were significantly (P < .05) lower in rats fed 0.5% and 1% EPA + DHA than those fed 0% EPA + DHA. Thiobarbituric acid-reactive substance content was significantly (P < .05) higher in 1% EPA + DHA-fed rats than in 0% and 0.5% EPA + DHA-fed rats. The level of 8-hydroxydeoxyguanosine was significantly (P < .05) higher in ICH rats with all diets than in sham surgery rats. Brain levels of EPA and DHA were highest in rats fed 1% EPA + DHA than in rats fed 0% and 0.5% EPA + DHA. These results suggested that intake of 1% EPA + DHA of total energy could lead to oxidative damage to the brain and thus increase the risk of intracerebral hemorrhagic stroke in this rat model.

The Effect of Hyperglycemia on Hypoperfusion-Induced Injury

Purpose. Because of differences in energy metabolism between the brain and retina, the hypothesis for the study was that, in a model of ocular and cerebral hypoperfusion, the retina would be protected by short-term hyperglycemia, whereas brain injury would be exacerbated. Methods. Hyperglycemia was induced by intraperitoneal streptozotocin. An initial experiment determined the effect of hyperglycemia alone in sham-surgery rats. Simultaneous retinal and cerebral hypoperfusion was achieved by two-vessel occlusion (2VO; permanent ligation of both common carotid arteries). Hyperglycemia was induced 3 days before 2VO by streptozotocin injection. The rats were killed 7 days after 2VO or sham surgery. The retina of one eye was collected for histology/immunohistochemistry and the fellow retina was collected for real-time RT-PCR. The retinas were analyzed for neuronal and glial markers and heat shock protein-27. The brains were processed for histology and immunohistochemistry. Results. Short-term (approximately 10 days) hyperglycemia alone caused no discernible injury to the retina. The retinas of the normoglycemic 2VO animals showed a marked loss of retinal ganglion cells and horizontal cells, thinning of the inner retina, glial cell activation, and infiltration of macrophages. The hyperglycemic 2VO rats displayed remarkable protection of the retinal structure and reduced glial cell activation compared with the normoglycemic 2VO animals. There was a significantly greater number of heat shock protein-27-positive retinal ganglion cells in the normoglycemic animals than in the hyperglycemic ones. Brains of both the normoglycemic and hyperglycemic 2VO animals displayed scattered ischemic infarcts and mild white matter injury. Conclusions. Short-term hyperglycemia affords robust protection against retinal hypoperfusion injury, but in the same animals, brain injury is not ameliorated. The mechanism of this retinal hyperglycemia-induced neuroprotection requires further study.

The Influence of p38 Mitogen-Activated Protein Kinase Inhibitor on Synthesis of Inflammatory Cytokine Tumor Necrosis Factor Alpha in Spinal Cord of Rats with Chronic Constriction Injury

Tumor necrosis factor alpha (TNF-alpha) could trigger p38 mitogen-activated protein kinase (MAPK) activation. Conversely phosphorylated p38 (p-p38) could induce the upregulation of TNF-alpha. In this study, we examined the hypothesis that chronic constrictive injury (CCI) of the sciatic nerve could promote spinal cord release of TNF-alpha and produce allodynia via the p38 MAPK pathway. Sprague-Dawley rats were divided into five groups: 1) naïve control rats, 2) sham surgery rats, 3) CCI surgery rats without treatment, 4) CCI surgery rats with saline (0.9%) treatment, and 5) CCI surgery rats with the p38 MAPK inhibitor SB203580 treatment. In treatment groups, saline or SB203580 (2 microg, twice a day) was given intrathecally starting 1 day before or 1 day or 7 days after CCI. All rats were killed at different times after surgery to examine p38 MAPK activity and TNF-alpha levels in the spinal cord by Western blot analysis or immunohistochemistry. Mechanical allodynia was tested by a series of von Frey hairs 3, 7, and 14 days after surgery. p-p38 MAPK was significantly increased at 3, 7, and 14 days after CCI surgery compared with time-matched shams (P < 0.05). Peripheral nerve injury induced mechanical allodynia and enhanced spinal concentrations of TNF-alpha (P < 0.05). Pretreatment or early treatment with SB203580 inhibited p38 MAPK activity, resulting in reduction of TNF-alpha synthesis and attenuation of mechanical allodynia (P < 0.05). p38 MAPK activation is one aspect of the signaling cascade that culminates in TNF-alpha synthesis and contributes to mechanical allodynia after peripheral nerve injury.

Increased Expression of 5-HT6 Receptors in the Rat Dorsomedial Striatum Impairs Instrumental Learning

A number of studies have shown that systemic 5-HT(6) receptor antagonists can improve learning and memory, but the mechanism for these observations is not known. As striatum normally expresses 5-HT(6) receptors abundantly and is important in consolidating stimulus-response learning, we used targeted gene delivery to further increase the expression of 5-HT(6) receptors in rat striatum and then examined learning. Increased 5-HT(6) expression had no effect on performance in the Morris water maze, a hippocampal-dependent learning paradigm, and did not alter the latency to approach or consume sucrose tablets. However, rats with increased 5-HT(6) expression failed to acquire a reward-based instrumental learning task, a striatum-dependent learning model, during 3 days of successive sessions as compared to sham surgery or GFP-expressing control rats. This behavioral deficit was observed in rats overexpressing 5-HT(6) receptors in the dorsomedial striatum, but not in rats with increased dorsocentral striatal expression. The 5-HT(6) receptor-associated deficit was reversed by administration of a 5-HT(6) antagonist, SB-258585, before each training session. When animals learned the instrumental learning task before gene transfer, increased 5-HT(6) receptor expression had no effect on long-term recall or performance of the task or on extinction of operant responding. Thus, 5-HT(6) receptor activity in rat striatum disrupts acquisition of new instrumental learning but does not impair memory or performance of reward-motivated behavior once established.

Liver and Skeletal Muscle Lipids Have Differing Fatty Acid Profiles in Short‐Gut Rats Fed via Parenteral Nutrition

In short-gut rats, we showed marked abnormalities in plasma lipid fatty acids using parenteral nutrition (PN) with lipid vs sham surgery rats. This suggests that either sensing or metabolism of parenteral lipid is abnormal in malabsorption. The goal of this study was to determine fatty acid profiles in skeletal muscle and liver in short-gut rats treated with PN compared with sham rats. Sprague-Dawley rats underwent laparotomy and massive small bowel resection (or sham surgery). Rats (n = 32, 16 sham, 16 short gut) were randomly assigned to PN with lipid or fat-free PN. After 5 days, weight loss was similar in all groups, and mixed hindlimb skeletal muscle and liver were biopsied. We found marked differences between liver and skeletal muscle. In livers of short-gut animals, 22:4omega6, 22:5omega6, and 22:6omega3 were higher (all p < .05) than in sham. In skeletal muscle, short gut had no effect on fatty acid profiles. In liver, fat-free PN led to significant increases in 20:3omega6, 22:4omega6, 22:5omega6, 20:3omega9, 20:5omega3, 22:6omega3, and triene/tetraene ratio (all p < .05) compared with feeding PN with lipid, irrespective of short gut. In muscle, levels of the distal long-chain fatty acid metabolites and triene/tetraene ratio were minimally affected by nutrition. Serum glucose and insulin concentrations were similar in all 4 groups. Both the presence of short gut and type of PN led to increases in distal metabolites of fatty acids on omega:3 and omega:6 pathway in liver phospholipids but not in skeletal muscle during short-term PN feeding in rats.

Limited role of macrophages in generation of nerve injury-induced mechanical allodynia

The purpose of this study was to investigate the role of peripheral macrophages in the generation of mechanical allodynia utilizing a modification of the Chung rat model of neuropathy. Three distinct methods were used: (1) systemic and perineural macrophage inhibition utilizing CNI-1493; (2) depletion of the peripheral macrophage population by liposome-encapsulated clodronate; and (3) perineural administration of activated or inactivated bone marrow-derived macrophages (BMDM) in sham-surgery rats. Mechanical allodynia was tested on days 1, 3, 5, 7, and 10 post-intervention or surgery using von Frey monofilaments. In order to assess the role of spinal glia following these interventions, microglial (CNS macrophages) and astrocytic activation was assessed using immunohistochemistry. CNI-1493 did not attenuate mechanical allodynia, or spinal glial expression as compared to the saline control group. Similarly, the clodronate depletion of peripheral macrophages prior to nerve injury did not have any effect on the resultant mechanical allodynia or spinal glial activation. Perineural administration of activated or inactivated BMDM did not evoke mechanical allodynia in sham surgery rats. Of interest, we observed an ipsilateral, dorsal horn increase in microglial expression following perineural administration of activated macrophages. In summary, these data suggest a limited role of activated macrophages in the onset of mechanical allodynia in an animal model of neuropathy.

Prevention of bone loss by percutaneous estradiol implants in ovariectomized rats

This study was conducted to investigate whether hydroxyapatite (HAP) is appropriate as a percutaneous drug carrier for estradiol (E2) for the suppression of bone loss. Ten-week-old female Sprague-Dawley rats were subjected either to bilateral ovariectomy (OVX) or to sham surgery (control). Ovariectomized rats were implanted percutaneously with E2-HAP disks containing low, medium or high doses of estradiol (50, 250, or 500 micrograms E2/rat, respectively). Ovariectomized rats without implant and OVX rats implanted only with HAP served as additional controls. All rats were sacrificed 90 days after surgery. At the end of the experiment, bone mineral density of the lumbar spine was measured by dual energy X-ray absorption, and serum E2 was assayed by radioimmunoassay. The bone mineral density of OVX and HAP-treated OVX rats decreased by 18% compared to sham surgery rats, but decreased by only 13, 7, and 3% in rats treated with 50, 250, and 500 micrograms E2/rat, respectively. The in vitro release of E2 from E2-HAP devices was determined by an HPLC method. Estradiol release from the HAP devices followed almost a zero-order kinetics. Estradiol remained intact in E2-HAP implants for up to six months when stored at 5, 25, and 40 degrees C. This study indicates that E2-HAP implants are effective in suppressing bone loss in the spine of OVX rats in a dose-dependent manner.