Quantitative determination of the biological activity of botulinum toxin type A by measuring the compound muscle action potential (CMAP) in rats

Model-based interspecies interpretation of botulinum neurotoxin type A on muscle-contraction inhibition

Botulinum neurotoxins (BoNTs) are commonly used in therapeutic and cosmetic applications. One such neurotoxin, BoNT type A (BoNT/A), has been studied widely for its effects on muscle function and contraction. Despite the importance of BoNT/A products, determining the blood concentrations of these toxins can be challenging. To address this, researchers have focused on pharmacodynamic (PD) markers, including compound muscle action potential (CMAP) and digit abduction scoring (DAS). In this study, we aimed to develop a probabilistic kinetic-pharmacodynamic (K-PD) model to interpret CMAP and DAS data obtained from mice and rats during the development of BoNT/A products. The researchers also wanted to gain a better understanding of how the estimated parameters from the model relate to the bridging of animal models to human responses. We used female Institute of Cancer Research mice and Sprague-Dawley (SD) rats to measure CMAP and DAS levels over 32 weeks after administering BoNT/A. We developed a muscle-contraction inhibition model using a virtual pharmacokinetic (PK) compartment combined with an indirect response model and performed model diagnostics using goodness-of-fit analysis, visual predictive checks (VPC), and bootstrap analysis. The CMAP and DAS profiles were dose-dependent, with recovery times varying depending on the administered dose. The final K-PD model effectively characterized the data and provided insights into species-specific differences in the PK and PD parameters. Overall, this study demonstrated the utility of PK-PD modeling in understanding the effects of BoNT/A and provides a foundation for future research on other BoNT/A products.

Up-regulation of cholesterol synthesis pathways and limited neurodegeneration in a knock-in Sod1 mutant mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder affecting brain and spinal cord motor neurons. Mutations in the copper/zinc superoxide dismutase gene ( SOD1 ) are associated with ∼20% of inherited and 1-2% of sporadic ALS cases. Much has been learned from mice expressing transgenic copies of mutant SOD1, which typically involve high-level transgene expression, thereby differing from ALS patients expressing one mutant gene copy. To generate a model that more closely represents patient gene expression, we created a knock-in point mutation (G85R, a human ALS-causing mutation) in the endogenous mouse Sod1 gene, leading to mutant SOD1 G85R protein expression. Heterozygous Sod1 G85R mutant mice resemble wild type, whereas homozygous mutants have reduced body weight and lifespan, a mild neurodegenerative phenotype, and express very low mutant SOD1 protein levels with no detectable SOD1 activity. Homozygous mutants exhibit partial neuromuscular junction denervation at 3-4 months of age. Spinal cord motor neuron transcriptome analyses of homozygous Sod1 G85R mice revealed up-regulation of cholesterol synthesis pathway genes compared to wild type. Transcriptome and phenotypic features of these mice are similar to Sod1 knock-out mice, suggesting the Sod1 G85R phenotype is largely driven by loss of SOD1 function. By contrast, cholesterol synthesis genes are down-regulated in severely affected human TgSOD1 G93A transgenic mice at 4 months. Our analyses implicate dysregulation of cholesterol or related lipid pathway genes in ALS pathogenesis. The Sod1 G85R knock-in mouse is a useful ALS model to examine the importance of SOD1 activity in control of cholesterol homeostasis and motor neuron survival.

SIGNIFICANCE STATEMENT

Amyotrophic lateral sclerosis is a devastating disease involving the progressive loss of motor neurons and motor function for which there is currently no cure. Understanding biological mechanisms leading to motor neuron death is critical for developing new treatments. Using a new knock-in mutant mouse model carrying a Sod1 mutation that causes ALS in patients, and in the mouse, causes a limited neurodegenerative phenotype similar to Sod1 loss-of-function, we show that cholesterol synthesis pathway genes are up-regulated in mutant motor neurons, whereas the same genes are down-regulated in transgenic SOD1 mice with a severe phenotype. Our data implicate dysregulation of cholesterol or other related lipid genes in ALS pathogenesis and provide new insights that could contribute to strategies for disease intervention.

Peripherally Administered Botulinum Toxin Type A Localizes Bilaterally in Trigeminal Ganglia of Animal Model

Peripheral nerve injury leads to sensory ganglion hyperexcitation, which increases neurotransmitter release and neuropathic pain. Botulinum toxin type A (BoNT/A) regulates pain transmission by reducing neurotransmitter release, thereby attenuating neuropathic pain. Despite multiple studies on the use of BoNT/A for managing neuropathic pain in the orofacial region, its exact mechanism of transport remains unclear. In this study, we investigated the effects of BoNT/A in managing neuropathic pain in two different animal models and its transport mechanism in the trigeminal nerve. Intraperitoneal administration of cisplatin induced bilateral neuropathic pain in the orofacial region, reducing the head withdrawal threshold to mechanical stimulation. Unilateral infraorbital nerve constriction (IONC) also reduced the ipsilateral head withdrawal threshold to mechanical stimulation. Unilateral peripheral administration of BoNT/A to the rat whisker pad attenuated cisplatin-induced pain behavior bilaterally. Furthermore, contralateral peripheral administration of BoNT/A attenuated neuropathy-induced behavior caused by IONC. We also noted the presence of BoNT/A in the blood using the mouse bioassay. In addition, the Alexa Fluor-488-labeled C-terminal half of the heavy chain of BoNT/A (BoNT/A-Hc) was localized in the neurons of the bilateral trigeminal ganglia following its unilateral administration. These findings suggest that axonal and hematogenous transport are involved in the therapeutic effects of peripherally administered BoNT/A in the orofacial region.

Recombinant botulinum neurotoxin serotype A1 in vivo characterization

Clinically used botulinum neurotoxins (BoNTs) are natural products of Clostridium botulinum. A novel, recombinant BoNT type A1 (rBoNT/A1; IPN10260) has been synthesized using the native amino acid sequence expressed in Escherichia coli and has previously been characterized in vitro and ex vivo. Here, we aimed to characterize rBoNT/A1 in vivo and evaluate its effects on skeletal muscle. The properties of rBoNT/A1 following single, intramuscular administration were evaluated in the mouse and rat digit abduction score (DAS) assays and compared with those of natural BoNT/A1 (nBoNT/A1). rBoNT/A1-injected tibialis anterior was assessed in the in situ muscle force test in rats. rBoNT/A1-injected gastrocnemius lateralis (GL) muscle was assessed in the compound muscle action potential (CMAP) test in rats. The rBoNT/A1-injected GL muscle was evaluated for muscle weight, volume, myofiber composition and immunohistochemical detection of cleaved SNAP25 (c-SNAP25). Results showed that rBoNT/A1 and nBoNT/A1 were equipotent and had similar onset and duration of action in both mouse and rat DAS assays. rBoNT/A1 caused a dose-dependent inhibition of muscle force and a rapid long-lasting reduction in CMAP amplitude that lasted for at least 30 days. Dose-dependent reductions in GL weight and volume and increases in myofiber atrophy were accompanied by immunohistochemical detection of c-SNAP25. Overall, rBoNT/A1 and nBoNT/A1 exhibited similar properties following intramuscular administration. rBoNT/A1 inhibited motoneurons neurotransmitter release, which was robust, long-lasting, and accompanied by cleavage of SNAP25. rBoNT/A1 is a useful tool molecule for comparison with current natural and future modified recombinant neurotoxins products.

The use of the dynamic weight bearing test to assess the effects of acute, intramuscularly administered botulinum neurotoxin type A1 in rats

Assessing the efficacy of botulinum neurotoxin (BoNT) in vivo is essential given the growing number of BoNT products used in the clinic. Here, we evaluated the dynamic weight bearing (DWB) test for sensitivity to paralytic effects of BoNT-A following intramuscular administration. The toxin was administered into the gastrocnemius lateralis as a single bolus or into the gastrocnemius lateralis and medialis as two boluses. The effects of BoNT-A in DWB were compared to those in the compound muscle action potential (CMAP) and the Digit Abduction Score (DAS) tests. Female Sprague-Dawley rats received an acute, intramuscular (i.m.) injection of BoNT-A1 (0.1, 1, 10 pg/rat) into the right gastrocnemius muscle, while the left received vehicle. The DWB and CMAP tests were performed one-two days after the injection in order to detect the onset of sub-maximal BoNT-A activity. Both tests were preceded by the DAS test. BoNT-A produced dose-related reductions in both the weight-bearing and surface-bearing outcomes of up to 60% while showing moderate activity in the DAS. BoNT-A effects in the DWB test were well-aligned with those in the CMAP test, which showed dose-dependent reductions in CMAP amplitude and the area under the curve (AUC; up to 100%) as well as increases in latency (up to 130%). The efficacy of BoNT-A in DWB and CMAP was more pronounced with two boluses. Thus, the DWB test can be used to assess the properties of BoNTs following i.m. administration. It can be used to assess the candidate therapies and is more ethical than the mouse lethality assay.

OnabotulinumtoxinA Displays Greater Biological Activity Compared to IncobotulinumtoxinA, Demonstrating Non-Interchangeability in Both In Vitro and In Vivo Assays

Differences in botulinum neurotoxin manufacturing, formulation, and potency evaluation can impact dose and biological activity, which ultimately affect duration of action. The potency of different labeled vials of incobotulinumtoxinA (Xeomin^®; 50 U, 100 U, or 200 U vials; incobotA) versus onabotulinumtoxinA (BOTOX^®; 100 U vial; onabotA) were compared on a unit-to-unit basis to assess biological activity using in vitro (light-chain activity high-performance liquid chromatography (LCA-HPLC) and cell-based potency assay (CBPA)) and in vivo (rat compound muscle action potential (CMAP) and mouse digit abduction score (DAS)) assays. Using LCA-HPLC, incobotA units displayed approximately 54% of the protease activity of label-stated equivalent onabotA units. Lower potency, reflected by higher EC₅₀, ID₅₀, and ED₅₀ values (pooled mean ± SEM), was displayed by incobotA compared to onabotA in the CBPA (EC₅₀: incobotA 7.6 ± 0.7 U/mL; onabotA 5.9 ± 0.5 U/mL), CMAP (ID₅₀: incobotA 0.078 ± 0.005 U/rat; onabotA 0.053 ± 0.004 U/rat), and DAS (ED₅₀: incobotA 14.2 ± 0.5 U/kg; onabotA 8.7 ± 0.3 U/kg) assays. Lastly, in the DAS assay, onabotA had a longer duration of action compared to incobotA when dosed at label-stated equivalent units. In summary, onabotA consistently displayed greater biological activity than incobotA in two in vitro and two in vivo assays. Differences in the assay results do not support dose interchangeability between the two products.

Can Botulinum-A Toxin Be Used to Delay Ejaculation: Results of an Ejaculation Model in Male Rats

INTRODUCTION

Although premature ejaculation (PE) is the most common sexual dysfunction in young men, its true pathophysiology has not yet been clearly elucidated.

AIM

To investigate the quantitative changes that occurred in an ejaculation model induced by para-chloroamphetamine (PCA) after botulinum-A toxin injection into the bulbospongiosus (BS) muscle in rats.

METHODS

A total of 21 male rats weighing 300 to 350 grams were used in the study. The animals were divided into 3 groups: control, 1 unit of botulinum-A toxin injected, and 5 units of botulinum-A toxin injected. The botulinum-A toxin was percutaneously injected into the BS muscle, and the experiment was carried out 96 hours (5 days) after the injection.

MAIN OUTCOME MEASURE

The seminal vesicle (SV) was cannulated, and the BS muscle was dissected and connected to an amplifier (Biopac; Goleta, CA) to record the pressure and electromyography measurement. The ejaculation parameters were obtained after the PCA injection.

RESULTS

The ejaculation latency time of the group receiving 5 units of botulinum-A toxin was statistically significantly longer (1092 ± 657 seconds) compared to the control group (298 ± 81 seconds) and the group receiving 1 unit of botulinum-A toxin (439 ± 100 seconds) (P = .003). Furthermore, the BS EMG area under the curve values for the group receiving 5 units of botulinum-A toxin were significantly lower (7.4 ± 1.2 V/s × 10-4) than those of the control group (13.6 ± 4.0 V/s × 10-4) and the group receiving 1 unit of botulinum-A toxin (13.6 ± 5.0 V/s × 10-4) (P = .009). No statistically significant difference was found between the groups in terms of the basal SV pressure, number of SV phasic contractions, maximum amplitude of the SV phasic contraction, and intervals between the SV phasic contractions and the BS muscle contractions.

CLINICAL IMPLICATIONS

Botulinum-A toxin injection is a potential treatment option for PE and should be further investigated by future clinical studies.

STRENGTHS AND LIMITATIONS

Ease of administration and prolonged duration of botulinum-A toxin are advantages of the existing treatment options. The risk of anejaculation due to the dosage should be kept in mind.

CONCLUSIONS

Injection of botulinum-A toxin into the BS muscle in rats significantly delayed the ejaculation latency time and affected the expulsion phase. Ongün S, Acar S, Koca P, et al. Can Botulinum-A Toxin Be Used to Delay Ejaculation: Results of an Ejaculation Model in Male Rats. J Sex Med 2019;16:1338-1343.

A comparison study of prabotulinumtoxinA vs onabotulinumtoxinA in myostatin-deficient mice with muscle hypertrophy

Botulinum toxin A (BoNT-A) is used clinically for various muscle disorders and acts by preventing the release of the neurotransmitter acetylcholine into the synapse space. Here, we compared the efficacy of prabotulinumtoxinA (PRA) and onabotulinumtoxinA (ONA) for the reduction in hypertrophy in myostatin-deficient (Mstn^-/- ) mice. Two different BoNT-A products (2.5, 10 and 25 U/kg) were injected to paralyse the hindlimb for 2 months, after which sciatic nerve conduction study, 3D micro-CT, haematoxylin and eosin (H&E) and dystrophin staining were conducted. Administration of BoNT-A products induced denervation-mediated atrophy and alleviated muscle hypertrophy generated in Mstn^-/- mice. The present study revealed that each BoNT-A regulates skeletal muscle size, myofibre number and myofibre diameter in Mstn^-/- mice. The potential applicability of BoNT-A for the treatment of rare muscle hypertrophic diseases was demonstrated. Compared with ONA, PRA had a comparable ability to act in the local area.

Extracorporeal shock wave treatment can selectively destroy end plates in neuromuscular junctions

INTRODUCTION

This study assesses the effect of radial extracorporeal shock wave (rESW) exposure on neuromuscular transmission and neuromuscular junction (NMJ) morphology.

METHODS

We applied 2,000 rESWs at 0.18 mJ/mm² and a frequency of 15 Hz to the right calf of male rats, measured the compound muscle action potential (CMAP), and examined NMJ morphology using electron microscopy. Left calf muscles were used as controls.

RESULTS

rESW exposure significantly reduced CMAP amplitude without delayed latency in exposed muscles compared with controls. All rESW-exposed muscles exhibited NMJs with irregular end plates. Mean interjunctional fold interval was significantly increased compared with controls. However, axon terminals and muscle fibers surrounding NMJs with irregular end plates were unchanged.

DISCUSSION

This localized destruction of end plates may be caused by differences in acoustic impedance induced by the density of acetylcholine receptors. These results provide a possible mechanism for the effectiveness of rESW treatment for spasticity and dystonia. Muscle Nerve 57: 466-472, 2018.

Comparison of Systemic Toxicity between Botulinum Toxin Subtypes A1 and A2 in Mice and Rats

The adverse events caused by botulinum toxin type A (subtype A1) product, thought to be after-effects of toxin diffusion after high-dose administration, have become serious issues. A preparation showing less diffusion in the body than existing drugs has been sought. We have attempted to produce neurotoxin derived from subtype A2 (A2NTX) with an amino acid sequence different from that of neurotoxin derived from subtype A1 (A1NTX). In this study, to investigate whether A2NTX has the potential to resolve these issues, we compared the safety of A2NTX, a progenitor toxin derived from subtype A1 (A1 progenitor toxin) and A1NTX employing the intramuscular lethal dose 50% (im LD50) in mice and rats and the compound muscle action potential (CMAP) in rats. Mouse im LD50 values for A1 progenitor toxin and A2NTX were 93 and 166 U/kg, respectively, and the rat im LD50 values were 117 and 153 U/kg, respectively. In the rat CMAP test, the dose on the contralateral side, which caused a 50% reduction in the CMAP amplitude, that is, CMAP-TD50 , was calculated as 19.0, 16.6 and 28.7 U/kg for A1 progenitor toxin, A1NTX and A2NTX, respectively. The results indicate that A2NTX is safer than A1 progenitor toxin and A1NTX.

Establishment of alternative potency test for botulinum toxin type A using compound muscle action potential (CMAP) in rats

The biological activity of botulinum toxin type A has been evaluated using the mouse intraperitoneal (ip) LD50 test. This method requires a large number of mice to precisely determine toxin activity, and, as such, poses problems with regard to animal welfare. We previously developed a compound muscle action potential (CMAP) assay using rats as an alternative method to the mouse ip LD50 test. In this study, to evaluate this quantitative method of measuring toxin activity using CMAP, we assessed the parameters necessary for quantitative tests according to ICH Q2 (R1). This assay could be used to evaluate the activity of the toxin, even when inactive toxin was mixed with the sample. To reduce the number of animals needed, this assay was set to measure two samples per animal. Linearity was detected over a range of 0.1-12.8 U/mL, and the measurement range was set at 0.4-6.4 U/mL. The results for accuracy and precision showed low variability. The body weight was selected as a variable factor, but it showed no effect on the CMAP amplitude. In this study, potency tests using the rat CMAP assay of botulinum toxin type A demonstrated that it met the criteria for a quantitative analysis method.

Spinal Central Effects of Peripherally Applied Botulinum Neurotoxin A in Comparison between Its Subtypes A1 and A2

Because of its unique ability to exert long-lasting synaptic transmission blockade, botulinum neurotoxin A (BoNT/A) is used to treat a wide variety of disorders involving peripheral nerve terminal hyperexcitability. However, it has been a matter of debate whether this toxin has central or peripheral sites of action. We employed a rat model in which BoNT/A1 or BoNT/A2 was unilaterally injected into the gastrocnemius muscle. On time-course measurements of compound muscle action potential (CMAP) amplitudes after injection of BoNT/A1 or BoNT/A2 at doses ranging from 1.7 to 13.6 U, CMAP amplitude for the ipsilateral hind leg was markedly decreased on the first day, and this muscle flaccidity persisted up to the 14th day. Of note, both BoNT/A1 and BoNT/A2 administrations also resulted in decreased CMAP amplitudes for the contralateral leg in a dose-dependent manner ranging from 1.7 to 13.6 U, and this muscle flaccidity increased until the fourth day and then slowly recovered. Immunohistochemical results revealed that BoNT/A-cleaved synaptosomal-associated protein of 25 kDa (SNAP-25) appeared in the bilateral ventral and dorsal horns 4 days after injection of BoNT/A1 (10 U) or BoNT/A2 (10 U), although there seemed to be a wider spread of BoNT/A-cleaved SNAP-25 associated with BoNT/A1 than BoNT/A2 in the contralateral spinal cord. This suggests that the catalytically active BoNT/A1 and BoNT/A2 were axonally transported via peripheral motor and sensory nerves to the spinal cord, where they spread through a transcytosis (cell-to-cell trafficking) mechanism. Our results provide evidence for the central effects of intramuscularly administered BoNT/A1 and BoNT/A2 in the spinal cord, and a new insight into the clinical effects of peripheral BoNT/A applications.

Relationship between ultrasonographic, electromyographic, and clinical parameters in adult stroke patients with spastic equinus: an observational study

OBJECTIVE

To find more accurate indices that could affect decisions in spasticity treatment by investigating the relation between ultrasonographic, electromyographic, and clinical parameters of the gastrocnemius muscle in adults with spastic equinus after stroke.

DESIGN

Observational study.

SETTING

University hospitals.

PARTICIPANTS

Chronic patients with stroke with spastic equinus (N=43).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Ultrasonographic features were spastic gastrocnemius muscle echo intensity, muscle thickness, and posterior pennation angle of the gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) in both legs. Electromyographic evaluation included compound muscle action potentials (CMAPs) recorded from the GM and GL of both legs. Clinical assessment of the spastic gastrocnemius muscle was performed with the Modified Ashworth Scale (MAS) and by measuring ankle dorsiflexion passive range of motion (PROM).

RESULTS

Spastic muscle echo intensity was inversely associated with proximal (GM and GL: P=.002) and distal (GM and GL: P=.001) muscle thickness, pennation angle (GM: P< .001; GL: P=.01), CMAP (GM: P=.014; GL: P=.026), and ankle PROM (GM: P=.038; GL: P=.024). The pennation angle was directly associated with the proximal (GM and GL: P< .001) and distal (GM: P=.001; GL: P< .001) muscle thickness of the spastic gastrocnemius muscle. The MAS score was directly associated with muscle echo intensity (GM: P=.039; GL: P=.027) and inversely related to the pennation angle (GM and GL: P=.001) and proximal (GM: P=.016; GL: P=.009) and distal (GL: P=.006) muscle thickness of the spastic gastrocnemius.

CONCLUSIONS

Increased spastic muscle echo intensity was associated with reduced muscle thickness, posterior pennation angle, and CMAP amplitude in the gastrocnemius muscle. Building on previous evidence that these instrumental features are related to botulinum toxin response, these new findings may usefully inform spasticity treatment decisions.

Comparison between botulinum neurotoxin type A2 and type A1 by electrophysiological study in healthy individuals

Botulinum neurotoxin type A1 (BoNTs/A1) and type B (BoNT/B) have been used for treating hyperactive muscle contractions. In the present study, we compared the effect of botulinum neurotoxin subtype A2 (6.5 mouse LD50 units A2 neurotoxin, A2NTX) and onabotulinumtoxinA (10 mouse LD50 units BoNT/A1 product) by measuring the compound muscle action potentials (CMAPs) before and after administration. In total, 8 healthy subjects were examined in the present study. A2NTX was injected into the extensor digitorum brevis (EDB) muscle, followed by onabotulinumtoxinA injection into the contralateral EDB muscle after 16 weeks. The CMAP amplitudes from the EDB, abductor hallucis (AH), and abductor digiti minimi pedis (ADM) muscles were measured after each BoNT injection on days 1, 3, 7, 14, 28, 56, 84, and 112 to assess the effect of the toxin. On day 14, both A2NTX and onabotulinumtoxinA produced an approximately 70% decline in EDB CMAP amplitude compared to the baseline values; significant reduction of the CMAP continued through day 112. The CMAP amplitudes from neighboring muscles (AH and ADM) remained intact throughout the study period, except for a slight but significant drop at day 28 after onabotulinumtoxinA injection compared to A2NTX. The current findings indicate that small doses (6.5 units and 10 units) of A2NTX and onabotulinumtoxinA have at least comparable onset and duration of action, although similar clinical effects were obtained with lower dose using A2NTX.

Electrophysiological study for comparing the effect of biological activity between type A botulinum toxins in rat gastrocnemius muscle

Background:

New cosmetic applications and products based on the effects of botulinum toxin (BTX) treatment have stimulated demand for this class of natural compounds. This demand generates the need for appropriate standardized protocols to test and compare the effectiveness of new BTX preparations.

Objectives:

Based on the previously described electrophysiological methods, we measured and compared the inhibitory effects of two BTX type A (BTX-A) preparations on neuromuscular transmission through split-body test.

Methods:

The effectiveness was evaluated in terms of the compound muscle action potential (CMAP) and conduction velocity after BTX-A injection. We used a split-body method to compare two different BTX-As in the rat.

Results:

Based on the changes in the CMAP, the two different BTX-As induced paralytic effect on the rat tibialis anterior muscle. However, the two different BTX-A preparations did not differ significantly in effectiveness and did not induce a delay in conduction velocity.

Conclusions:

The new BTX-A preparation used in this electrophysiological study had similar effect compared with the previously marketed BTX-A.[AQ: Please approve the edits made to the sentence “The new BTX-A preparation…”) We propose that a split-body electrophysiological protocol will be useful in establishing the comparative effectiveness of new BTX products.

Impairment of spinal motor neurons in spinocerebellar ataxia type 1-knock-in mice

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of polyglutamine repeats in the Ataxin-1 protein. An accumulating body of cerebellar, histological and behavioral analyses has proven that SCA1-knock-in mice (in which the endogenous Atxn1 gene is replaced with mutant Atxn1 that has abnormally expanded 154 CAG repeats) work as a good tool, which resembles the central nervous system pathology of SCA1 patients. However, the peripheral nervous system pathology of the model mice has not been studied despite the fact that the clinical manifestation is also characterized by peripheral involvement. We show here that spinal motor neurons are degenerated in SCA1-knock-in mice. Histologically, some spinal motor neurons of the SCA1-knock-in mice have polyglutamine aggregates in their nuclei and also thinner and demyelinated axons. Electrophysiological examinations of the mice showed slower nerve conduction velocities in spinal motor neurons and lower amplitudes of muscle action potential, compared to wild-type mice. Consistently, the mice displayed decrease in rearing number and total rearing time. These results suggest that the knock-in mice serve as a definite model that reproduces peripheral involvement and are therefore useful for research on the peripheral nervous system pathology in SCA1 patients.

Degeneration and recovery of the neuromuscular junction after application of extracorporeal shock wave therapy

It is known that free nerve endings are degenerated after application of shock waves. We therefore hypothesized that the application of shock waves to muscle induces dysfunction of neuromuscular transmission at neuromuscular junctions. We investigated changes in neuromuscular transmission in response to shock wave application. Sprague-Dawley rats were used in this study. Two thousand shock waves at an energy flux density of 0.18 mJ/mm(2) were applied to their right calf muscles. Neuromuscular junctions of gastrocnemius muscles were evaluated using rhodamine-α-bungarotoxin on the day of treatment (n  =  5). Amplitude and latency of compound muscle action potentials were measured on the day of treatment and 1, 2, 4, 6, and 8 weeks after treatment (n  =  10, each group). Degenerated acetylcholine receptors existed in all treated muscles. Although the action potential amplitude on the treated side was significantly less than on the control side from the day of treatment (25.1 ± 7.8 vs. 34.5 ± 9.1, p  =  0.012) to 6 weeks (27.9 ± 7.2 vs. 34.5 ± 7.2, p  =  0.037), there was no significant difference at 8 weeks. There was no significant difference in transmission latency between the groups. The application of shock waves to muscle induced a transient dysfunction of nerve conduction at neuromuscular junctions.

Active coping with stress suppresses glucose metabolism in the rat hypothalamus

We used 18F-fluorodeoxyglucose small-animal positron-emission tomography to determine whether different styles of coping with stress are associated with different patterns of neuronal activity in the hypothalamus. Adult rats were subjected to immobilization (IMO)-stress or to a non-immobilized condition for 30 min, in random order on separate days, each of which was followed by brain-scanning. Some rats in the immobilized condition were allowed to actively cope with the stress by chewing a wooden stick during IMO, while the other immobilized rats were given nothing to chew on. Voxel-based statistical analysis of the brain imaging data shows that chewing counteracted the stress-induced increased glucose uptake in the hypothalamus to the level of the non-immobilized condition. Region-of-interest analysis of the glucose uptake values further showed that chewing significantly suppressed stress-induced increased glucose uptake in the paraventricular hypothalamic nucleus and the anterior hypothalamic area but not in the lateral hypothalamus. Together with the finding that the mean plasma corticosterone concentration at the termination of the IMO was also significantly suppressed when rats had an opportunity to chew a wooden stick, our results showed that active coping by chewing inhibited the activation of the hypothalamic-pituitary-adrenal axis to reduce the endocrine stress response.