Hind Feet Of Rats Research Articles

Effect of acupuncture at "Houxi" (SI3) and"Huantiao" (GB30) on high mobility group box 1 protein in spinal nerve trunk of rats with lumbar disc herniation

To observe the effect of acupuncture at "Houxi"(SI3) and "Huantiao"(GB30) on high mobility group box 1(HMGB1) protein and mRNA in spinal nerve trunk(SNT) of rats with lumbar disc herniation(LDH), so as to explore the mechanisms of acupuncture at this paired points on the treatment for LDH. SD rats were randomly divided into sham operation, model, conventional acupuncture(CA) and paired points(PP) groups (with 8 rats in each group). The LDH model was established by injection of autologous suspension made from rats' own nucleus pulsus into the epidural space. Rats in the CA group received acupuncture treatment at bilateral "Weizhong"(BL40), "Dachangshu"(BL25) and "Shenshu"(BL23), while rats in the PP group received acupuncture at bilateral SI3 and GB30, 30 min each time, once daily for 14 consecutive days. The thermal pain threshold of bilateral hind feet of rats was detected by thermal pain stimulator. The contents of serum IL-1β, IL-6 and IL-8 of rats were detected by ELISA. Western blot and immunofluorescence were used to detect the expression of HMGB1 protein in the lumbar(L)5 SNT of rats. The relative expression of HMGB1 mRNA in L5 SNT was determined by qPCR. HE staining was used to observe the morphological changes of L5 SNT. Compared with the sham operation group, the thermal pain threshold of bilateral hind feet in the model group was decreased (P<0.05); compared with the model group, the thermal pain threshold of bilateral hind feet in the CA group and the PP group were increased (P<0.05). The expressions of HMGB1 protein and mRNA in L5 SNT, and the contents of serum IL-1β, IL-6 and IL-8 of rats in the model group were significantly increased(P<0.000 1, P<0.001) in contrast to the sham operation group. The expressions of HMGB1 protein and mRNA in L5 SNT, and the levels of serum IL-1β, IL-6 and IL-8 were significantly decreased (P<0.01, P<0.000 1, P<0.001, P<0.05) in the CA and PP group, in comparison with those of the model group. Compared with the CA group, the above indexes of rats in the PP group recovered more significantly (P<0.05,P<0.001, P<0.01,P<0.000 1). The histomorphological results showed scattered and various-sized nerve fibers, vacuolation, a large number of disintegrating myelin sheath and lysed Schwann cells in the model group. Myelin sheaths regeneration, regularly-arranged nerve fibers were seen in the CA group and the PP group, with more obvious histopathological recovery observed in the PP group than the CA group. Acupuncture intervention inhibites the expressions of HMGB1 protein and mRNA in rats with LDH, and further reduces the production of IL-1β, IL-6 and IL-8, which is beneficial to inflammatory response inhibition and pain alleviation. The therapeutic effect of the PP group is more obvious than that of the CA group.

Antiperspirant effects and mechanism investigation of Mulisan decoction in rats based on plasma metabolomics

Context Mulisan decoction (MLS) is a classic formula of traditional Chinese medicine for treating hyperhidrosis. The mechanism remains unclear. Objective To investigate the antiperspirant effect and underlying mechanisms of MLS. Materials and methods Fifty rats were divided into control, model, and three doses of MLS intervention groups (n = 10). Rats except for control group were induced diseases features of the applicable scope of MLS via i.p. reserpine (0.5 mg/kg/d) for 10 days. From day 11, MLS groups were administrated orally MLS at 0.6, 3, and 15 g/kg once a day for 14 days, respectively. After the last administration, sweating was induced in all rats via s.c. pilocarpine (25 mg/kg), the right hind foot of rats was stained, and sweat point numbers were observed. Rat serum was collected to detect IL-2, IL-6, IFN-γ, and TNF-α. Rat plasma was collected for endogenous metabolite analysis via UPLC-QE-Focus-MS. Results Rats treated with MLS presented a significant decrease in sweat point numbers (13.5%), increase in body weight (13.2%), and promotion in the balance of Th1/Th2 cytokine ratio via increasing IL-2 (38.3%), IFN-γ (20.1%), and TNF-α (22.0%) and decreasing IL-6 (24.7%) compared with the model group (p < 0.05). Plasma metabolomics disclosed 15 potential biomarkers related to model rats, of which two could be significantly reversed by MLS (p < 0.05). The involved pathways were pantothenate and CoA biosynthesis, and porphyrin metabolism. Conclusions MLS demonstrated a good antiperspirant effect and metabolism improvement. These findings inspire more clinical study validation on immune improvement and antiperspirant effect.

Demonstrating Hairy and Glabrous Skin Innervation in a 3D Pattern Using Multiple Fluorescent Staining and Tissue Clearing Approaches.

Skin innervation is an important part of the peripheral nervous system. Although the study of the cutaneous nerve fibers has progressed rapidly, most of the understanding of their distributional and chemical characteristics comes from conventional histochemical and immunohistochemical staining on thin tissue sections. With the development of the tissue clearing technique, it has become possible to view the cutaneous nerve fibers on thicker tissue sections. The present protocol describes multiple fluorescent staining on tissue sections at a thickness of 300 µm from the plantar and dorsal skin of rat hindfoot, the two typical hairy and glabrous skin sites. Here, the calcitonin gene-related peptide labels the sensory nerve fibers, while phalloidin and lymphatic vessel endothelial hyaluronan receptor 1 label the blood and lymphatic vessels, respectively. Under a confocal microscope, the labeled sensory nerve fibers were followed completely at a longer distance, running in bundles in the deep cutaneous layer and freestyle in the superficial layer. These nerve fibers ran in parallel to or surrounded the blood vessels, and lymphatic vessels formed a three-dimensional (3D) network in the hairy and glabrous skin. The current protocol provides a more effective approach to studying skin innervation than the existing conventional methods from the methodology perspective.

Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin

Sympathetic denervation and impaired angiogenesis cause skin diseases. However, the relationship between the sympathetic nervous system and vascular cell turnover in normal skin remains unclear. To determine the effects of sympathetic denervation on vascular cell turnover in normal skin. Rats underwent bilateral L2-4 sympathetic trunk resection (sympathectomy group) or sham operation (control). Hindfoot plantar skin was analyzed 2 weeks and 3 months postoperatively. Mural cell marker (α-smooth muscle actin; p < 0.001, and desmin; p = 0.047) expression decreased 2 weeks after sympathectomy, but recovered 3 months after sympathectomy (p > 0.05). CD31 levels were lower in the experimental group than in the control group at 2 weeks (p = 0.009), but not at 3 months. Von Willebrand factor, vascular endothelial growth factor, and angiopoietin-2 expression were not significantly different between the groups (p > 0.05). Angiopoietin-1 expression levels were higher in the experimental group than in the control group at 2 weeks (p = 0.035), but not at 3 months. Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin by inhibiting mural cell proliferation and increasing angiopoietin-1 expression. Sympathetic nerves therefore play an important role in plantar skin vascular cell turnover.

Effect of activated autologous monocytes/macrophages on wound healing in a rodent model of experimental diabetes

AimWe aimed to evaluate the effectiveness of the application of activated autologous monocytes/macrophages (Mo/Mp) on wound healing in diabetic rats. MethodsSixty male SD rats were equally divided into the following: control group (normal, nondiabetic), PBS-treated diabetic group, and tumor necrotic factor alpha (TNF-α) plus interferon-γ (IFN-γ)-stimulated or unstimulated Mo/Mp-treated diabetic group. Full-thickness round wounds (1cm×1cm) were created in the right hind foot of rats and the wounds were treated with PBS or Mo/Mp on day 1 after injury. In the following 14 days, the percentage of wound contraction was measured, histologic examination was performed with hematoxylin and eosin staining, and vascular endothelial growth factor (VEGF) in the wound was evaluated by Western blot analysis. ResultsDiabetic rats exhibited impaired wound healing with delayed angiogenesis and VEGF expression. The early application of TNF-α plus IFN-γ-stimulated autologous Mo/Mp to diabetic wounds significantly improved the delayed wound healing through the stimulation of angiogenesis and re-epithelization, as well as restoring the defect in VEGF expression. ConclusionsMo/Mp activated by TNF-α and IFN-γ promotes diabetic wound healing and normalizes the defect in VEGF regulation associated with diabetes-induced skin-repair disorders.

Preventive Effects of Phyllanthus urinaria Extract on Paw Edema in Adjuvant‐Induced Arthritis Rats

The aim of this study was to examine the preventive effects of Phyllanthus urinaria Extract (PUE) on paw edema in adjuvant‐induced arthritis (AA) rats. Arthritis was induced by the injection of 200 ul of a suspension of 10 mg/ml heat‐killed tuberculosis (Mycobacterium tuberculosis) into the plantar region of the right hind foot of rats. Paw edema of the right hind feet of AA rats were reduced by the administration of PUE for 14 days and 28 days after adjuvant injection in comparison with those of AA rats administered physiological saline. The beta‐sitosterol had similar effect as the PUE applied. Myeloperoxydase activity (MPO) was reduced by the PUE in AA rats. These results indicate that the PUE are effective as anti‐inflammatory agents in AA rats and their action is markedly influenced by the inhibition of neutrophil migration into inflamed tissue. Therefore, these findings may provide the pharmacological basis of the clinical usage of PUE in treatment of inflammation.

Effect of erhuangfang on cerebral and spinal demyelination and regeneration as well as expression of glial fibrillary acidic protein in rats with experimental allergic ncephalomyelitis

Background It demonstrates that erhuangfang can improve clinical symptoms of multiple sclerosis and relieve side effects of hormone. However, whether erhuangfang can improve experimental allergic encephalomyelitis (EAE) or not needs a further study. Objective To observe the effect of erhuangfang on neuro-pathology and astrocyte in EAE rats and compare with the effect of hormone. Design Randomized controlled animal study. Settings Department of Traditional Chinese Medicine, Beijing Tiantan Hospital, Capital Medical University; College of Traditional Chinese Medicine, Capital Medical University. Materials The experiment was carried out in the Laboratory Center of Capital Medical University from August to October 2005. Ten adult guinea pigs (SPF grade, weighing 400–450 g) and 70 adult Lewis rats (SPF grade, weighing 200–220 g) were selected in this study. Erhuangfang consisted of jiudahuang, shengdi, shuizhi, dabeimu, etc. Methods ▪ Experimental intervention: Rats were randomly divided into normal group ( n=10), model group (n=20), western medicine group ( n=20) and Chinese herb group ( n=20). Mixed emulsion, which was consisted of Freund's adjuvant and spinal cord homogenate of guinea pigs, was subcutaneously injected into palms of the two hindfeet of rats in the latter three groups to establish EAE models. Foot pads were injected with saline and then rats were perfused with saline in the normal group. In the model group, models were established as the same as those mentioned above, and rats were also perfused with saline. Rats in the western medicine group were perfused with saline and then 5 mg/kg prednisone acetate suspension. Rats in the Chinese herb group were perfused with erhuangfang decoction (15 g raw materials per kilogram) at 5 days before model establishment. The dosage in the four groups was 3 mL/day per rat. ▪ Experimental evaluation: At 28 days after model establishment, rats were randomly selected for cerebral (mainly surrounding cerebral ventricle) and spinal cord (cervical enlargement and lumbar enlargement) collections, and then haematine-eosin (HE) staining and SLG myelin staining were used to observe demyelination and regeneration; meanwhile, immunohistochemical staining was used to observe the expression of glial fibriliary acidic protein (GFAP). Main outcome measures Cerebral and spinal demyelination and regeneration as well as expression of GFAP in EAE rats. Results All 70 Lewis rats were involved in the final analysis. ▪ Demyelination and regeneration: Infiltration of inflammatory cells surrounding cerebrum and small venous vessels of spinal cord white matter, demyelination surrounding vessels and plentiful foam cells at myelinolysis sites were observed in the model group. Symptoms were relieved in the western medicine group and the Chinese herb group as compared with those in the model group. While, numbers of inflammatory infiltrated cells and vascular cuffs were decreased in focal region as compared with those in the model group; in addition, areas of softening focus and demyelination were decreased. ▪ Expression of GFAP: Volumes and numbers of positive cells of GFAP in white matter region were respectively bigger and higher than those of normal cells in the model group. Plentiful positive cells of GFAP were disorderly aggregated in hippocampus and surrounding small vessel cuffs. While, expression of GFAP was mildly increased surrounding focus in the Chinese herb group; however, GFAP did not express surrounding focus in the western medicine group. In addition, expressions of GFAP were not increased in non-focal region in both Chinese herb group and western medicine group. Conclusion Both erhuangfang and hormone can relieve inflammatory reaction of central nervous system and demyelination of EAE rats. On one hand, erhuangfang can regulate reaction of astrocyte in two ways, relieve reaction and proliferation of astrocyte in non-focal region and maintain the protective effect of astrocyte on brain tissue in focal region; on the other hand, hormone can overall inhibit reaction of astrocyte.

A Collagen Prolyl 4-hydroxylase Inhibitor Reduces Adhesions after Tendon Injury

Collagen synthesis inhibition potentially can reduce adhesion formation after tendon injury but also may affect cutaneous wound healing. We hypothesized that a novel orally administered collagen synthesis inhibitor (CPHI-I) would substantially reduce flexor tendon adhesions after injury, without any clinically important effect on cutaneous wound healing. The experiments were performed in a rat model with an in-continuity crush injury model in the rat hindfoot flexor tendon to provoke adhesion formation. Assays of dermal collagen production and the rate of healing of an excised wound were performed to assess cutaneous wound healing. Animals in the treatment groups received CPHI-I for 1, 2, or 6 weeks and were assessed at either 2 or 6 weeks. The work of flexion in the injured digit was reduced in the CPHI-I-treated animals compared with control animals, (0.188 J versus 0.0307 J at 2 weeks, and 0.0231 J versus 0.0331 J at 6 weeks) The cutaneous wound healing rate was similar in all animals, but dermal collagen synthesis was reduced in the treated animals. The CPHI-I seems to reduce tendon adhesion, and although collagen synthesis was reduced in cutaneous wounds, CPHI-I did not retard wound healing.

Influence of capsaicin cream in rats with peripheral neuropathy

We investigated the effect of topical application of capsaicin cream on withdrawal latency in the hind foot of rat in response to radiant heat in an experimental model of neuropathic pain. A neuropathic state was induced by loose ligation of the sciatic nerve with chromic gut suture. A marked thermal hyperalgesia was observed in response to heat stimulus applied to the operated side from 3 days through 2 weeks, followed by a gradual return to the control level by 35 days after surgery. Capsaicin cream applied to both the bilateral hind instep and sole once a day for a continuous period of 2 weeks or 4 weeks alleviated thermal hyperalgesia in a dose-dependent manner. A remarkable effect was observed 2 weeks after the start of the application and this effect proved to be reversible. On the other hand, in sham-operated animals when capsaicin cream was applied once daily from day 7 after the sham operation, from 1 day through 3 weeks following capsaicin application, withdrawal latency of the sham-operated paws of the capsaicin-treated group was significantly increased as compared to that of the vehicle cream-treated group. The effects of antagonists of glutamate receptor and tachykinin receptors were investigated 7 days post surgery. Pretreatment with MK-801 (0.5 mg kg−1, i.p.), but not with CNQX (0.5 mg kg−1, i.p.), reversed the thermal hyperalgesia following nerve injury. Neither of RP67580 (1–10 mg kg−1, i.p.) nor SR48968 (1–10 mg kg−1, i.p.) had any effect on the withdrawal latency in the injured and non-injured hind paw. These results suggest that although the manifestation of effectiveness may be delayed by changes in networks of neurotransmitters related to the nociceptive pathways following nerve injury, longer-term repetitive application of capsaicin cream has a significant therapeutic effect on subjects with painful peripheral neuropathy.

SCH 58261, an A(2A) adenosine receptor antagonist, counteracts parkinsonian-like muscle rigidity in rats.

The aim of the present study was to find out whether blockade of adenosine A(2A) receptors by a selective antagonist, SCH 58261, influenced parkinsonian-like muscle rigidity. Muscle tone was examined using a combined mechano- and electromyographic method which simultaneously measured muscle resistance (MMG) of a rat hindfoot to passive extension and flexion in the ankle joint and electromyographic activity (EMG) of the antagonistic muscles of that joint: gastrocnemius and tibialis anterior. Muscle rigidity produced by reserpine (5 mg/kg + alpha-methyl-p-tyrosine, 250 mg/kg) was antagonized by SCH 58261 (0.1-5 mg/kg). SCH 58261 (5 mg/kg) also reduced reserpine-enhanced tonic and reflex EMG activities in both the gastrocnemius and the tibialis muscles. Moreover, SCH 58261 in doses of 1 and 5 mg/kg abolished muscle resistance induced by haloperidol (0.5 mg/kg). However, only the highest dose of SCH 58261 (5 mg/kg) decreased tonic EMG activity enhanced by haloperidol. Administration of L-DOPA (75 and 100 mg/kg) dose-dependently decreased the muscle resistance as well as tonic EMG activity evoked by haloperidol. Combined administration of SCH 58261 (0.1 mg/kg) and L-DOPA (50 mg/kg) in doses which did not affect the haloperidol-induced muscle rigidity produced a pronounced synergistic effect. The ability of SCH 58261 to diminish the parkinsonian-like muscle rigidity and to potentiate the effect of L-DOPA in this model seems to indicate a therapeutic value of this compound in the treatment of Parkinson's disease.

The role of metabotropic glutamate receptor (mGluR) ligands in parkinsonian muscle rigidity.

It has been shown that the primary striatal dopaminergic hypofunction which is at the origin of Parkinson's disease, results in a secondary hyperactivity of glutamatergic neurotransmission. In the search for a therapy of Parkinson's disease, ionotropic, mainly NMDA, receptor antagonists were found to have moderately beneficial, yet also some undesirable side-effects. Therefore the present study was aimed at determining whether some metabotropic glutamate receptor (mGluR) ligands may have antiparkinsonian effects in the haloperidol-induced muscle rigidity. To this end three mGluR ligands were used: the potent and selective mGluR I antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), the mixed group II agonist/ group I antagonist (S)-4-carboxy-3-hydroxyphenyl-glycine ((S)-4-C3HPG), and the potent group II agonist (+)-2-aminobicyclo[3.1.0.]hexane-2,6,-dicarboxylic acid (LY354740). Only LY354740 penetrated the brain from the periphery; for this reason other drugs were injected bilaterally into the rostral striatum or nucleus accumbens. The muscle tone was recorded by a mechanomyographic/electromyographic (MMG/EMG) method which measured the resistance of a rat's hind foot and the EMG reflex response of its muscles to passive movements. (S)-4C3HPG (5 and 15 microg/0.5 microl) and LY354740 (5 and 10mg/kg i.p.) diminished the muscle rigidity induced by haloperidol (1 mg/kg i.p.). AIDA (0.5-15 microg/0.5 microl) injected into the striatum was only slightly effective in the highest dose used. However, when injected into the nucleus accumbens AIDA (15microg/0.5microl) significantly and strongly counteracted the haloperidol-induced muscle rigidity. Our results suggest that stimulation of group II striatal mGluRs seems to play a major role in diminution of parkinsonian-like muscle rigidity. However, it seems that the antagonism of group I mGluRs located in the nucleus accumbens may also be of importance to the antiparkinsonian effect.

Effect of acute and chronic administration of 1,2,3,4-tetrahydroisoquinoline on muscle tone, metabolism of dopamine in the striatum and tyrosine hydroxylase immunocytochemistry in the substantia nigra, in rats

The effects of acute and chronic administration of 1,2,3,4-tetrahydroisoquinoline, an endogenous substance suspected of producing parkinsonism in humans, on the muscle tone and metabolism of dopamine in the striatum, and on the number of tyrosine hydroxylase-immunoreactive cells in the substantia nigra were investigated in rats. Muscle tone was examined using a combined mechanomyographic and electromyographic method which measured simultaneously the muscle resistance of the rat's hind foot to passive extension and flexion in the ankle joint and electromyographic activity of the antagonistic muscles of that joint: gastrocnemius and tibialis anterior. 1,2,3,4-Tetrahydroisoquinoline administered at doses of 50 and 100 mg/kg intraperitoneally for 19 days increased muscle resistance 1 h after the first injection (acute treatment), 1 h after the last injection (chronic treatment) and three days after compound withdrawal. Rigidity observed on the third day of 1,2,3,4-tetrahydroisoquinoline withdrawal was accompanied by an increased tonic (resting) electromyographic activity of the gastrocnemius and tibialis anterior muscles. At the same time, a significant reduction in the number of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra and a decrease in the dopamine level in the striatum were also found. A declining number of tyrosine hydroxylase-immunoreactive neurons in the whole substantia nigra showed a significant negative correlation with the enhanced muscle resistance, as well as with the tonic electromyographic activity recorded at rest, i.e. before the start of movements, from the gastrocnemius and tibialis anterior muscles. Our results suggest that 1,2,3,4-tetrahydroisoquinoline may be one of the endogenous substances involved in the progress of Parkinson's disease.

Contribution of the glycine site of NMDA receptors in rostral and intermediate-caudal parts of the striatum to the regulation of muscle tone in rats

The aim of the present study was to assess the contribution of the glycine site of NMDA receptors in the striatum to the regulation of muscle tone. Muscle tone was examined using a combined mechano and electromyographic method, which measured simultaneously the muscle resistance (MMG) of the rat's hind foot to passive extension and flexion in the ankle joint and the electromyographic activity (EMG) of the antagonistic muscles of that joint: gastrocnemius and tibialis anterior. Muscle rigidity was induced by haloperidol (2.5 mg/kg i.p.). 5,7-dichlorokynurenic acid (5,7-DCKA), a selective glycine site antagonist, injected in doses of 2.5 and 4.5 μg/0.5 μl bilaterally, into the rostral region of the striatum, decreased both the haloperidol-induced muscle rigidity (MMG) and the enhanced electromyographic activity (EMG). 5,7-DCKA injected bilaterally in a dose of 4.5 μg/0.5 μl into the intermediate-caudal region of the striatum of rats not pretreated with haloperidol had no effect on the muscle tone. The present results suggest that blockade of the glycine site of NMDA receptors in the rostral part of the striatum may be mainly responsible for the antiparkinsonian action of this drug.

The developmental skeletal growth in the rat foot is reduced after denervation.

It has long been known that bone is innervated. In recent years it has been suggested that the local nerves may influence the growth and metabolism of bone by way of neuropeptides. The transient local presence of nerve-containing cartilage canals just before formation of secondary ossification centres in rat knee epiphyses seems to support that view. The purpose of the present study was to see if denervation affects the developmental growth of metatarsal bones in the rat hindfoot. We made sciatic and femoral neurectomies in 7-day-old rat pups and examined the hindfeet at various times after surgery. Immunohistochemical analysis showed that denervation was complete. Radiographic examination revealed that the metatarsal bones were significantly shorter in denervated hindfeet 30 days after denervation (average relative shortening 9.9 +/- 2.3%). Measurements of total foot length showed that denervated feet were subnormally sized already five days postoperatively, before the onset of secondary ossification. The timing of the latter was not affected by denervation. Control rats subjected to tenotomies exhibited normal metatarsal bone lengths. On the basis of these results we suggest that the local nerves may influence the growth of immature bones but do not affect secondary ossification.

The influence of dizocilpine (MK-801) on the reserpine-enhanced electromyographic stretch reflex in rats

The electromyographic (EMG) stretch reflex in the gastrocnemius and tibialis anterior muscles was elicited by passive bending and stretching of the rat's hind foot in the ankle joint. The EMG stretch reflex was increased by pretreatment with reserpine (10 mg/kg ip) which is a model compound commonly used to induce parkinsonian rigidity in laboratory animals. Dizocilpine (MK-801) (0.32, 0.64 and 1.28 mg/kg sc) inhibited long-latency supraspinal components of the reserpine-increased EMG stretch reflex, whereas a short-latency spinal component was not diminished. The present results suggest that MK-801 exhibits an antiparkinsonian action against reserpine-induced rigidity.

Distal tibial mononeuropathy in diabetic and nondiabetic rats reared on wire cages: an experimental entrapment neuropathy

Using electrophysiological recordings, we studied a distal tibial mononeuropathy that involves the hind foot of rats reared in cages with wire grid flooring. In an initial set of experiments, serial sciatic-tibial motor conduction recordings were made in smaller or larger rats reared in cages with wire grid or sawdust flooring. Electrophysiological features of the neuropathy were loss in the amplitude of the distal tibial nerve M potential recorded over hind limb foot muscles, temporal dispersion of the potential, often into multiple peaks, and a prolonged distal latency of the response. The changes in M amplitude were more apparent in larger rats with a greater body weight. In a second series of experiments we studied sciatic-tibial conduction over 16 weeks in nondiabetic rats and rats rendered diabetic with streptozotocin raised and wire grid or plastic flooring. Tibial mononeuropathy developed in both wire grid-reared groups, but there was evidence that it appeared earlier in diabetic rats. Electrophysiological changes of distal mononeuropathy also obscured the expected slowing of sciatic-tibial motor conduction velocity from diabetics. Tibial mononeuropathy in rats reared on wire grid flooring may be a useful animal model of human entrapment neuropathy but its presence can confound studies of experimental neuropathy. Rats used in studies of experimental neuropathy should be housed in plastic cages with sawdust or shavings flooring.

The immunosuppressant FK506 increases the rate of axonal regeneration in rat sciatic nerve

The axonal regenerative properties of the new immunosuppressant drug FK506 (tacrolimus) are further explored in this continuing study. In an initial report (Gold et al., 1994a), we described the ability of FK506 to reduce the time until return of function in the hind feet of rats following a sciatic nerve crush. In the present study, we examined the morphological correlate underlying this enhancement of functional recovery. In rats receiving daily subcutaneous injections of FK506 (1.0 mg/kg) for 18 d following a sciatic nerve crush the regenerating axons appeared larger in size compared to saline-injected control animals. Morphometric analysis of axonal calibers in the soleus nerve demonstrated that mean axonal areas for the largest 30% of axons were increased over axotomized control values by 93% in the FK506-treated animals. Next, the rate of axonal regeneration was determined by radiolabeling the L5 dorsal root ganglion (DRG) at 9 and 14 d following axotomy. Regression analysis of the outgrowth distances for sensory axons between 10 and 15 d revealed a 16% increase in regeneration rate. Electron microscopy of intramuscular nerve branches in the interosseus muscles confirmed that the axons in the FK506-treated animals were further advanced toward their targets; in some instances, axons were shown to reinnervate muscle spindles. The results are discussed in terms of the known ability of FK506 to inhibit the activity protein phosphatase 2B (calcineurin).

Functional evaluation of regenerated and misrouted axons to glabrous and hairy skin of the rat hind foot after sciatic neurotomy and suture

The function of misrouted regenerated polymodal nociceptor C-fibers and low-threshold mechanoreceptive axons in the lateral plantar nerve (LPN) and in the foot branch of the superficial peroneal nerve (fSPN) was evaluated 3 months after unilateral sciatic neurotomy and suture. Two weeks before evaluation the tibial fascicle (or the peroneal fascicle) above the neurotomy was cut and tied off. In this way only functional regeneration of misrouted axons was tested in the LPN (or the fSPN). In regenerated animals the glabrous skin area had no functional fSPN-related low-threshold mechanoreceptive axons. However, the hairy fSPN skin area showed function of misrouted LPN-related low-threshold mechanoreceptive axons. In both the glabrous skin domain innervated by the LPN and the hairy skin area supplied by the fSPN, functional regeneration of misrouted polymodal nociceptor C-fibers was found. We conclude that functional regeneration of misrouted axons related to polymodal nociceptive units and low-threshold mechanoreceptive units is more efficient in hairy skin of the rat foot whereas only misrouted polymodal nociceptor C-fibers recover function in glabrous skin.

Functional Projection of Sensory Lateral Plantar and Superficial Peroneal Nerve Axons to Glabrous and Hairy Skin of the Rat Hindfoot after Sciatic Nerve Lesions

The functional regeneration of C-fibers mediating polymodal nociception and low-threshold mechanoreceptive axons in the lateral plantar nerve (LPN) and the foot branch of the superficial peroneal nerve (fSPN) was evaluated in normal rats and 3 months after unilateral sciatic nerve crush or neurotomy and suture. The area covered by low-threshold mechanoreceptors (LTMs) was tested through gentle mechanical skin stimulation and recording from the relevant nerve. In regenerated animals the glabrous skin area with functional LPN-related LTMs was severely reduced following a crush lesion. Functional receptors of that type were absent after neurotomy and suture. The hairy skin area with fSPN-related LTMs was smaller than normal, particularly following neurotomy and suture. The distribution of polymodal C-fibers was tested through stimulation-induced extravasation of Evans blue albumin (EBA). In the glabrous LPN skin domain the area showing EBA extravasation did not return to normal after any of the lesion types. However, in the hairy fSPN skin area the distribution of EBA extravasation appeared largely normal following both injuries. We conclude that polymodal nociception reappears to a greater extent than low threshold mechanosensitivity, and that both modalities regenerate better in hairy skin than in glabrous skin.

Antiparkinsonian action of MK-801 on the reserpine-induced rigidity: a mechanomyographic analysis.

MK-801, a non-competitive antagonist of NMDA receptors, is known to exhibit a beneficial action in many animal models of Parkinson's disease. The aim of this study was to examine the influence of MK-801 on the reserpine-induced muscle rigidity. The rigidity was estimated by a direct mechanomyographic method. This method consists in successive bending and straightening of a rat's hind foot in the ankle joint and measuring the resistance of the foot to passive movements. Reserpine in doses of 5-10 mg/kg ip, given alone or in combination with alpha-methyl-p-tyrosine (alpha MT, 250 mg/kg ip), induced rigidity. The strongest muscle rigidity was induced by 10 mg/kg of reserpine 1 hour after administration. MK-801 (0.32-1.28 mg/kg sc) injected 70 min after reserpine (10 mg/kg ip) decreased the rigidity induced by the latter compound. Similarly, MK-801 (1.28 mg/kg sc), administered 27 h 40' after joint treatment with reserpine (10 mg/kg ip) and alpha MT (250 mg/kg ip), strongly inhibited the reserpine-induced muscle rigidity. The obtained results show that the glutamatergic hyperactivity plays a significant role in the reserpine-induced rigidity. As the reserpine-induced motor disturbances are commonly accepted to be an animal model of parkinsonian symptoms, it may be assumed that the NMDA receptor blocking component may contribute substantially to the therapeutic action of antiparkinsonian drugs.