Functional recovery from sciatic nerve crush lesion in the rat correlates with individual differences in responses to chronic intermittent stress

Effects of Exercise on Neuropathy in Streptozotocin-Induced Diabetic Rats

Objective

To evaluate the effects of early regular exercise and to assess the electrophysiological and histopathological findings of the rat tail nerve in relation to the timing of exercise training for swimming exercise in rats with diabetic neuropathy.

Methods

We used 70 Sprague-Dawley male rats, and the experimental group comprised 60 rats, and the control group comprised 10 rats. Diabetes was induced by intraperitoneal injection of streptozotocin. Blood glucose concentrations were measured in tail vein blood samples. The experimental group was divided into 6 subgroups according to insulin treatment and swimming exercise: group 1, diabetic control; group 2, insulin treated; group 3, insulin untreated with early swimming exercise; group 4, insulin treated and early swimming exercise; group 5, insulin treated and late swimming exercise; and group 6, insulin untreated with late swimming exercise. Sensory and motor nerve conduction studies were performed weekly up to the 13th week using rat tail nerves. The effect on structural diabetic neuropathy was assessed by morphometry and ultrastructural examination of the rat tail nerve fiber at the 14th week.

Results

An exercise effect was observed in the insulin treated groups, but it was not observed in the insulin untreated groups. The sensory nerve conduction study in the rat tail revealed significantly prolonged latency and decreased amplitude in groups 1 and 6, and a further delay was observed in group 5 when compared to group 4. Decreased thickness of myelin was found in groups 1 and 6 through morphometry.

Conclusion

Early regular exercise programs in addition to conventional insulin treatment may retard the progression of diabetic peripheral neuropathy.

Effects of swimming exercise on nerve regeneration in a rat sciatic nerve transection model

Background: Swimming is commonly considered to be an efficient rehabilitation exercise to treat peripheral nerve injury. However, the most effective resistance level and exercise duration is still unclear. We investigated the effects and mechanisms of swimming at various exertion levels in a rat sciatic nerve transection model.

Methods: Sciatic nerve transection rats were randomized into the following four groups based on swimming duration (from the 7th day to the 28th day post-surgery): sedentary control group (SC), S10 group (10 min/3 times/week), S20 group (20 min/3 times/week), and S30 group (30 min/3 times/week) (n = 10 each). Axon regeneration, electrophysiological properties, muscular weights, macrophage infiltration, and nerve repair associated maker, calcitonin gene-related peptide (CGRP), were measured.

Results: Dramatic higher successful percentages of nerve regeneration across the 10-mm gaps in swimming groups compared to the SC group. Total area of nerve regeneration significantly improved in the S10 group; however, electrophysiological properties, muscular weights, and macrophage infiltration in the regenerated nerves of rats did not differ significantly between the various exercise groups. CGRP expression was significantly increased in the spinal cord of rats in the S20 group.

Conclusions: Our data indicated that CGRP-related axonal regeneration improved significantly with moderate swimming. These results should inspire new studies in physiotherapeutic practice for related human treatment.

Whisking recovery after automated mechanical stimulation during facial nerve regeneration

IMPORTANCE Recovery from facial nerve transection is typically poor, but daily mechanical stimulation of the face in rats has been reported to remarkably enhance functional recovery after facial nerve transection and suture repair. This phenomenon needs additional investigation because of its important clinical implications. OBJECTIVE To determine whether automated mechanical stimulation of the whisker pad improves whisking recovery after facial nerve transection and repair in a rat model. DESIGN AND SETTING Sixty-one rats underwent unilateral facial nerve transection and suture repair and were randomized into 8 groups. Six groups received daily automated whisker or whisker pad mechanical stimulation including 0.5-, 1.5-, and 8.0-Hz patterns. Two control groups received restraint without stimulation. Treatment started on postoperative day 8, occurred 5 days per week, and lasted throughout 15 weeks of recovery. Whisking amplitude, velocity, and acceleration were quantified weekly for 15 weeks. INTERVENTIONS Unilateral facial nerve transection, suture repair, and, for 6 groups, daily automated whisker or whisker pad mechanical stimulation. MAIN OUTCOMES AND MEASURES Quantification of whisking amplitude, velocity, and acceleration. RESULTS Rats receiving the low frequencies of stimulation of the whiskers or whisker pad did not demonstrate enhanced whisking recovery, and rats receiving stimulation at 8.0 Hz showed significantly worse whisking recovery compared with controls and previously published groups receiving lower dose manual stimulation. CONCLUSIONS AND RELEVANCE Although daily manual whisker pad stimulation has been shown to enhance whisking recovery, rats in this study did not demonstrate improved whisking recovery after automated mechanical stimulation across a wide range of driving frequencies. Moreover, faster stimulation (8.0 Hz) was actually detrimental to recovery. Further work is needed to understand the relationship between stimulation patterns and the physiologic mechanisms underlying improved or worsened functional outcomes after facial nerve transection and repair.

Passive and active exercise improve regeneration and muscle reinnervation after peripheral nerve injury in the rat

INTRODUCTION

Lesions of peripheral nerves cause loss of motor and sensory function and also lead to hyperreflexia and hyperalgesia. Activity-dependent therapies promote axonal regeneration and functional recovery and may improve sensory-motor coordination and restoration of adequate circuitry at the spinal level.

METHODS

We compared the effects of passive (bicycle) and active (treadmill) exercise on nerve regeneration and modulation of the spinal H reflex after transection and repair of the rat sciatic nerve. Animals were evaluated during 2 months using electrophysiological, functional, and histological methods.

RESULTS

Moderate exercise for 1 hour/day, either active treadmill walking or passive cycling, improved muscle reinnervation, increased the number of regenerated axons in the distal nerve, and reduced the increased excitability of spinal reflexes after nerve lesion.

DISCUSSION

Maintenance of denervated muscle activity and afferent input, by active or passive exercise, may increase trophic factor release to act on regenerating axons and to modulate central neuronal plasticity.

Limbic and HPA axis function in an animal model of chronic neuropathic pain

Chronic pain can be considered a form of chronic stress, and chronic pain patients often have disturbances of the hypothalamic-pituitary-adrenal (HPA) axis, including abnormal cortisol levels. In addition, chronic pain patients have an increased incidence of depression and anxiety, stress-related disorders that are frequently accompanied by disturbances in the limbic system (e.g. hippocampus and amygdala) and the HPA axis. Despite the fact that the literature supports a strong link between chronic pain, stress disorders, and limbic dysfunction, the mechanisms underlying the effects of chronic pain on the HPA axis and limbic system are not understood. The current study employs a rodent neuropathic pain model (chronic constriction injury (CCI) of the sciatic nerve) to assess the long-term impact of chronic pain on the HPA axis and limbic system. Adult male rats received CCI or sham surgery; nociceptive behavioral testing confirmed CCI-induced neuropathic pain. Tests of HPA axis function at 13-23 days postsurgery demonstrated that CCI did not affect indices of basal or restraint stress-induced HPA axis activity. CCI increased the expression of corticotrophin releasing hormone mRNA in the central amygdala, and not the paraventricular nucleus of the hypothalamus or the bed nucleus of the stria terminalis. Moreover, glucocorticoid receptor mRNA expression in CCI rats was increased in the medial and central amygdala, unaffected in the paraventricular nucleus, and decreased in the hippocampus. These results suggest that increased nociceptive sensitivity during chronic pain is associated with alterations in the limbic system, but is dissociated from HPA axis activation.

Yasargil-Phynox aneurysm clip: a simple and reliable device for making a peripheral nerve injury

A great number of devices were used to make a peripheral nerve injury. In the scientific literature, experimental crush injuries have been usually created using forceps or hemostatic forceps, neither of which allows quantitative or standard application of compression. Therefore, we used a Yasargil-Phynox aneurysm clip to make a reliable and standardized peripheral nerve injury. The advantages and disadvantages of this clip were discussed. In particular, we think that standardization of the compression is necessary to compare interlaboratory results.

Effects of Erkang, a modified formulation of Chinese folk medicine Shi-Quan-Da-Bu-Tang, on mice

Shi-Quan-Da-Bu-Tang is a traditional Chinese herbal medicine formula used to increase vital energy, and strengthen health and immunity. Data from previous studies demonstrated that this formula also has the ability to attack tumor tissue. The Erkang capsule is a modified formula of Shi-Quan-Da-Bu-Tang, with the addition of four other herbs to increase the adaptogen effects and ergogenic properties. Results from this study in mice indicated that the Erkang treated group had significant differences in mortality, body weight change, fatigue, cold temperature endurance, and immune function related organ weight change, compared to the control animals.

Recovery of function after sciatic nerve crush lesion in rats selected for diverging locomotor activity in the open field

The relation between recovery of function following a sciatic nerve crush lesion and an individual behavioural characteristic, the locomotor activity in an open field, was investigated in rats. Ten high-active (HA) and ten low-active (LA) rats were selected from a stock of sixty male, random-bred Wistar rats, by measuring travelled distance in an open field. Subsequently, both HA and LA rats underwent an unilateral sciatic nerve crush. Recovery of motor function revealed no significant differences between both groups, whereas recovery of sensory function in HA rats was significantly more rapid than in the LA rats (P < 0.01). These observations suggest the existence of a relationship between individual behavioural characteristics, and the sensory recovery of nerve function following crush lesion in rats.