Quadriceps muscle activity during walking with a knee ankle foot orthosis is associated with improved gait ability in acute hemiplegic stroke patients with severe gait disturbance.

Introduction: A knee-ankle-foot orthosis (KAFO) prevents knee buckling during walking and enables gait training for acute hemiplegic stroke patients with severe gait disturbances. Although the goal of gait training with a KAFO is to improve gait ability, that is, to acquire walking with an ankle-foot orthosis (AFO), it is not clear how gait training with a KAFO contributes to improving gait ability. Therefore, this study aimed to investigate the relationship between muscle activities during walking with a KAFO and the improvement of gait ability in hemiplegic stroke patients with severe gait disturbance. Methods: A prospective cohort study was conducted. Fifty acute hemiplegic stroke patients who could not walk with an AFO participated. Muscle activities of the paretic rectus femoris, biceps femoris, tibialis anterior, and soleus were assessed with surface electromyogram during walking with a KAFO. Electromyograms were assessed at the beginning of gait training and at the time the Ambulation Independence Measure score improved by 3 or higher, or discharge. Results: Even in patients with complete hemiplegia, paretic rectus femoris, biceps femoris, and soleus showed periodic muscle activity during walking with a KAFO. Twenty-three patients improved to an Ambulation Independence Measure score of 3 or higher and were able to walk with an AFO (good recovery group). At the beginning of gait training, paretic rectus femoris muscle activity during the first double-limb support phase was significantly higher in the good recovery group than in the poor recovery group. The rectus femoris muscle activity significantly increased from before to after acute rehabilitation, which consisted mainly of gait training with a KAFO. Discussion: For acute hemiplegic stroke patients with severe disturbance, the induction and enhancement of paretic quadriceps muscle activity during walking with a KAFO play an important role in acquiring walking with an AFO.

Novel characteristics of the temporal transition to maximum tongue pressure in Parkinson's disease: A pilot study.

Introduction: The reason why maximum tongue pressure (MTP) decreases in patients with Parkinson's disease (PD) remains unclear. Repeated measurements of isometric force and MTP may be useful for analyzing muscle wasting and force generation. The purpose of this pilot study was to evaluate the clinical characteristics and temporal transition of MTP in PD and normal control (NC) groups. Methods: There were 18 participants in this study: 10 with PD and 8 NCs. The MTP was measured 20 times at regular intervals. The area under the curve of MTP temporal transitions, time to reach MTP, and total transition time of the tongue pressure (time to return to baseline) were compared between the groups. Results: MTP decreased from baseline in PD subjects. Unlike NCs, PD subjects showed diverse and inconsistent temporal transitions. The decrease in MTP and delays in time to reach MTP and time to return to baseline were significantly greater in PD subjects (p < 0.05), while there was no group difference in area under the curve values. According to repeated-measures ANOVA, MTP was not different over time between PD subjects and NCs. Conclusion: In this study, muscle fatigue did not affect the decrease in MTP seen in PD subjects, or the diversity and inconsistency of the temporal transition in MTP in that group. These findings indicate that the motor control needed for the repeated, identical movements associated with MTP generation may be impaired in PD patients.

A Case of Tardive Dystonia with Task Specificity Confined to the Lower Extremities only during Walking.

Background: Task-specific dystonia (TSD) confined to the lower extremities (LE) is relatively rare. This report describes dystonia confined to the LE only during forward walking. This case required careful neurological and diagnostic assessment because the patient was taking several neuropsychiatric drugs that cause symptomatic dystonia, such as aripiprazole (ARP). Case: A 53-year-old man visited our university hospital with a complaint of abnormalities in the LE that appeared only during walking. Neurological examinations other than walking were normal. Brain magnetic resonance imaging revealed meningioma in the right sphenoid ridge. The patient had been treated for depression with neuropsychiatric medications for a long time, and his abnormal gait appeared about 2 years after additional administration of ARP. After the meningioma was removed, his symptoms remained. Surface electromyography showed dystonia in both LE during forward walking, although his abnormal gait appeared to be accompanied by spasticity. The patient was tentatively diagnosed with tardive dystonia (TD). Although dystonia did not disappear clinically, it was alleviated after discontinuing ARP. Administration of trihexyphenidyl hydrochloride and concomitant rehabilitation improved his dystonia until return to work, but some residual gait abnormalities remained. Discussion: We report an unusual case of TD with task specificity confined to the LE. The TD was induced by the administration of ARP in combination with multiple psychotropic medications. Careful consideration was required for clinical diagnosis, rehabilitation, and assessment of its relevance to TSD.

New Artificial Intelligence-Integrated Electromyography-Driven Robot Hand for Upper Extremity Rehabilitation of Patients With Stroke: A Randomized, Controlled Trial.

BACKGROUND: An artificial intelligence (AI)-integrated electromyography (EMG)-driven robot hand was devised for upper extremity (UE) rehabilitation. This robot detects patients' intentions to perform finger extension and flexion based on the EMG activities of 3 forearm muscles. OBJECTIVE: This study aimed to assess the effect of this robot in patients with chronic stroke. METHODS: This was a single-blinded, randomized, controlled trial with a 4-week follow-up period. Twenty patients were assigned to the active (n = 11) and control (n = 9) groups. Patients in the active group received 40 minutes of active finger training with this robot twice a week for 4 weeks. Patients in the control group received passive finger training with the same robot. The Fugl-Meyer assessment of UE motor function (FMA), motor activity log-14 amount of use score (MAL-14 AOU), modified Ashworth scale (MAS), H reflex, and reciprocal inhibition were assessed before, post, and post-4 weeks (post-4w) of intervention. RESULTS: FMA was significantly improved at both post (P = .011) and post-4w (P = .021) in the active group. The control group did not show significant improvement in FMA at the post. MAL-14 AOU was improved at the post in the active group (P = .03). In the active group, there were significant improvements in wrist MAS at post (P = .024) and post-4w (P = .026). CONCLUSIONS: The AI-integrated EMG-driven robot improved UE motor function and spasticity, which persisted for 4 weeks. This robot hand might be useful for UE rehabilitation of patients with stroke.Clinical Trial Registry Name: The effect of robotic rehabilitation using XMM-HR2 for the paretic upper extremity among hemiparetic patients with stroke.Clinical Trial Registration-URL: https://jrct.niph.go.jp/Unique Identifier: jRCTs032200045.

Factor analysis for construct validity of a trunk impairment scale in Parkinson's disease: a cross-sectional study.

Objectives: To investigate the construct validity of the Trunk Impairment Scale (TIS), which was developed to assess trunk impairment in patients with stroke, in patients with Parkinson's disease (PD). Design: This retrospective, cross-sectional study enrolled consecutive PD inpatients. Correlation analysis was performed to clarify whether the TIS assessment was related to other balance functions, lower extremity muscle strength, or walking ability. Factor analysis was performed to see how the background factors of TIS differ from balance function, lower limb muscle strength, and walking ability. Results: Examining the data of 471 patients with PD, there were relationships between TIS and the Mini-Balance Evaluation Systems Test (r = 0.67), Barthel Index (r = 0.57), general lower limb extension torque (r = 0.51), two-minute walk test (r = 0.54), Hoehn and Yahr stage (r = -0.61), and Movement Disorder Society Unified Parkinson's Disease Rating Scale part III total points (r = -0.59). Factor analysis showed that TIS items were divided into three factors (an abdominal muscles and righting reflex component; a perception and verticality component; and a rotational component), differing from other scales that included clinical assessment items. Conclusion: The TIS can be useful for assessing the underlying trunk impairment as a basis for activities of daily living, gait function, and balance ability in patients with PD.

Prediction of gait independence using the Trunk Impairment Scale in patients with acute stroke.

Background: Gait recovery is one of the primary goals of stroke rehabilitation. Gait independence is a key functional component of independent activities in daily living and social participation. Therefore, early prediction of gait independence is essential for stroke rehabilitation. Trunk function is important for recovery of gait, balance, and lower extremity function. The Trunk Impairment Scale (TIS) was developed to assess trunk impairment in patients with stroke. Objective: To evaluate the predictive validity of the TIS for gait independence in patients with acute stroke. Methods: A total of 102 patients with acute stroke participated in this study. Every participant was assessed using the TIS, Stroke Impairment Assessment Set (SIAS), and Functional Independence Measure (FIM) within 48 h of stroke onset and at discharge. Gait independence was defined as FIM gait scores of 6 and 7. Multiple regression analysis was used to predict the FIM gait score, and multiple logistic regression analysis was used to predict gait independence. Cut-off values were determined using receiver operating characteristic (ROC) curves for variables considered significant in the multiple logistic regression analysis. In addition, the area under the curve (AUC), sensitivity, and specificity were calculated. Results: For the prediction of the FIM gait score at discharge, the TIS at admission showed a good-fitting adjusted coefficient of determination (R 2 = 0.672, p < 0.001). The TIS and age were selected as predictors of gait independence. The ROC curve had a TIS cut-off value of 12 points (sensitivity: 81.4%, specificity: 79.7%) and an AUC of 0.911. The cut-off value for age was 75 years (sensitivity: 74.6%, specificity: 65.1%), and the AUC was 0.709. Conclusion: The TIS is a useful early predictor of gait ability in patients with acute stroke.

Short-Term Motor Outcomes in Parkinson's Disease after Subthalamic Nucleus Deep Brain Stimulation Combined with Post-Operative Rehabilitation: A Pre-Post Comparison Study.

Background: The effects of subthalamic nuclear deep brain stimulation therapy (STN-DBS) and combined postoperative rehabilitation for patients with Parkinson's disease with postural instability have yet to be well reported. This study investigated the effects of short-term postoperative rehabilitation with STN-DBS on physical function in patients with Parkinson's disease. Methods: Patients diagnosed with Parkinson's disease who were admitted to our hospital for STN-DBS surgery were included in this study. Data were prospectively collected and retrospectively analyzed. Postoperative rehabilitation consisted of muscle-strengthening exercises, stretching, and balance exercises for 40-60 minutes per day for approximately 14 days. The Mini-Balance Evaluation Systems Test (Mini-BESTest), Timed Up and Go test (TUG) seconds and steps, Trunk Impairment Scale (TIS), seconds for 10 times toe-tapping, lower limb extension torque using StrengthErgo240, and center of pressure sway in the quiet standing posture were evaluated preoperatively, postoperatively, and at discharge. Mini-BESTest changes were also evaluated in the two groups classified by the presence or absence of postural instability. One-way and two-way repeated measures analyses of variance were performed for each of the three periods of change, and paired t-tests with the Bonferroni method were performed as multiple comparison tests. A stepwise multiple regression model was used to identify factors associated with balance improvement. Results: A total of 60 patients with Parkinson's disease were included, and there were significant increases in Mini-BESTest, TIS, StrengthErgo240, and postural sway during closed-eye standing compared to pre- and postoperative conditions at discharge (p < 0.05), and they decreased significantly compared to the postoperative period (p < 0.05). On stepwise multiple regression analysis, decreased steps of TUG and improvement of TIS scores were related to improvement of the Mini-BESTest (p < 0.05). In addition, Mini-BESTest scores in both groups with and without postural instability were significantly increased at discharge compared to preoperative and postoperative conditions (p < 0.01). Conclusion: Postoperative rehabilitation combined with STN-DBS may provide short-term improvements in physical function compared with the preoperative medicated status. The improvements in gait step length and trunk function may be important factors for obtaining improvement of postoperative postural stability.

The MMT of Elbow Flexion and the AFE Predict Impairment and Disability at 3 Weeks in Patients With Acute Stroke.

Objective: This study aimed to investigate whether upper extremity motor function assessment within 72 h from stroke onset can predict the functional outcomes of the upper extremity. Design: This was a prospective, cohort study of patients with a first unilateral hemispheric stroke between May 2018 and March 2020. The motor arm item of the National Institutes of Health Stroke Scale, manual muscle testing of the elbow and forearm, and active finger extension scale were assessed within 72 h after stroke onset. The Fugl-Meyer assessment upper extremity motor score and action research arm test were assessed at discharge from the acute hospital. Multiple regression analysis was used to study predictors of upper extremity motor function at discharge from the acute hospital. The adjustment variables included age, sex, thumb localizing test, and visuospatial function. Results: Sixty acute stroke patients were recruited. The model with the highest coefficient of determination for the Fugl-Meyer assessment upper extremity motor score at discharge was the elbow flexion model (R 2 = 0.76), followed by the active finger extension model (R 2 = 0.69). For the action research arm test, the highest model was the active finger extension model (R 2 = 0.64), followed by the elbow flexion model (R 2 = 0.63). Conclusion: The manual muscle testing of elbow flexion and the active finger extension may be useful for predicting impairment and disability at 3 weeks in patients with acute stroke.

The development of Ambulation Independence Measure: A new measurement tool to assess gait ability in acute stroke patients.

BACKGROUND: The assessment of gait function is important for stroke rehabilitation. Gait function of patients with stroke often depends on the type of orthosis. There are however few gait assessments that assess the type of orthosis. OBJECTIVE: The purpose of this study was to investigate the reliability and validity of our newly developed Ambulation Independence Measure (AIM), which assesses the gait function, type of orthoses and physical assistance, for acute stroke patients. METHODS: A total of 73 acute stroke patients participated in this prospective study. The AIM discriminates 7 levels of gait ability on the basis of the amount of physical assistance required and orthoses that are used during walking. Interrater reliability, concurrent validity with the Functional Ambulation Category (FAC) and predictive validity were examined. RESULTS: The weighted kappas of AIM at the start of gait training (baseline) and discharge were 0.990 and 0.978, respectively. The AIM scores were significantly correlated with the FAC scores at both baseline (r = 0.808) and discharge (r = 0.934). Multiple regression analyses showed that the AIM at baseline was a stronger predictor of the FAC at discharge (R2 = 0.80). CONCLUSIONS: The AIM has excellent reliability, concurrent validity, predictive validity, and good responsiveness in acute stroke patients.

Trunk Impairment as a Predictor of Activities of Daily Living in Acute Stroke.

Background and purpose: Trunk function plays a key role in performing activities of daily living (ADL) including locomotion and sitting. Sitting and ADL should be performed as early as possible especially during the acute phase of stroke rehabilitation. Therefore, this study aimed to assess trunk function among patients with acute stroke using the Trunk Impairment Scale (TIS) and to predict its functional outcomes. Methods: Overall, 67 patients with acute stroke (i.e., within 2 days of occurrence of the stroke) were included. The following clinical assessment items were obtained within 48 h after stroke onset and on the day before discharge from the hospital. Trunk function was examined using TIS and Trunk Control Test (TCT). The motor function of the upper and lower extremities was assessed using the stroke impairment assessment set motor (SIAS-M) score, and ADL was assessed using functional independence measure motor (FIM-M) items. Results: Multiple regression analysis was performed using the stepwise regression method, using the total FIM-M score following discharge as the dependent variable and age, TIS, TCT, SIAS-M, and FIM-M within 48 h after stroke onset as the independent variables. Age, TIS, and FIM-M within 48 h after stroke onset were selected as the input variables and showed a high-adjusted determination coefficient (R2 = 0.79; P < 0.001). Conclusion: TIS is a reliable method for evaluating trunk control function and is an early predictor of ADL among patients with acute stroke.

Balance and Gait Improvements of Postoperative Rehabilitation in Patients with Parkinson's Disease Treated with Subthalamic Nucleus Deep Brain Stimulation (STN-DBS).

BACKGROUND: Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a surgical treatment to reduce the "off" state motor symptoms of Parkinson's disease (PD). Postural instability is one of the major impairments, which induces disabilities of activities of daily living (ADLs). The effectiveness of STN-DBS for postural instability is unclear, and the effect of rehabilitation following STN-DBS has remained uncertain. OBJECTIVE: The purpose of this study was to examine changes in balance ability, gait function, motor performance, and ADLs following 2 weeks of postoperative rehabilitation in PD patients treated with STN-DBS. METHODS: Sixteen patients were reviewed retrospectively from February 2016 to March 2017. All patients were tested in their "on" medication state for balance and gait performance using the Mini-Balance Evaluation Systems Test (Mini-BESTest) and the Timed "Up and Go" (TUG) test before the operation, after the operation, and during the discharge period. The UPDRS motor score (UPDRS-III) and Barthel Index (BI) were assessed before the operation and during the discharge period. Rehabilitation focused on muscle strengthening with stretching and proactive balance training. Friedman's test and the post hoc Wilcoxon's signed-rank test were used to analyze the balance assessments, and ANOVA and the post hoc Tukey's test were used to analyze gait performance. The significance level was p < 0.05. RESULTS: During the discharge period, the Mini-BESTest and TUG were significantly improved compared with the preoperative and postoperative periods (p < 0.05). There were no differences between preoperative and postoperative periods in the Mini-BESTest (p=0.12) and TUG (p=0.91). The BI and motor sections of the UPDRS did not differ significantly between the preoperative and postoperative periods (p=0.45, p=0.22). CONCLUSION: The results of this study suggest that postoperative rehabilitation improves balance and gait ability in patients with PD treated with STN-DBS.

Priming With Intermittent Theta Burst Transcranial Magnetic Stimulation Promotes Spinal Plasticity Induced by Peripheral Patterned Electrical Stimulation.

This study explored the effect of corticospinal activity on spinal plasticity by examining the interactions between intermittent theta burst transcranial magnetic stimulation (iTBS) of the motor cortex and peripheral patterned electrical stimulation (PES) of the common peroneal nerve (CPN). Healthy volunteers (n = 10) received iTBS to the tibialis anterior (TA) muscle zone of the motor cortex and PES of the CPN in three separate sessions: (1) iTBS-before-PES, (2) iTBS-after-PES, and (3) sham iTBS-before-PES. The PES protocol used 10 100-Hz pulses every 2 s for 20 min. Reciprocal inhibition (RI) from the TA to soleus muscle and motor cortical excitability of the TA and soleus muscles were assessed at baseline, before PES, and 0, 15, 30, and 45 min after PES. When compared to the other protocols, iTBS-before-PES significantly increased changes in disynaptic RI for 15 min and altered long-loop presynaptic inhibition immediately after PES. Moreover, the iTBS-induced cortical excitability changes in the TA before PES were correlated with the enhancement of disynaptic RI immediately after PES. These results demonstrate that spinal plasticity can be modified by altering cortical excitability. This study provides insight into the interactions between modulation of corticospinal excitability and spinal RI, which may help in developing new rehabilitation strategies.

Effect of vibration stimulation on dysbasia of spastic paraplegia in neuromyelitis optica: a possible example of neuronal plasticity.

We analysed the effect of vibration stimulation (VS) on dysbasia of neuromyelitis optica (NMO). The patient was a 36-year-old woman who was diagnosed with NMO and had difficulties in walking. VS was applied to the lower limb muscles on the left, more spastic, side with an ordinary vibrator. The performance of standing up and walking improved with VS. Even with improved performance after VS, the amount of surface EMG of the lower limbs did not increase as a whole, but the EMG patterns among the lower leg muscles changed remarkably. VS produced reciprocity within antagonistic muscles. Variability of EMG amplitudes decreased remarkably during the walking cycle, not only on the vibrated side, but also on the non-vibrated side. The effect lasted longer than several dozen minutes after the cessation of VS. We conjectured that central pattern generator (CPG) and neuronal plasticity were the result of VS.

Identification of neurite outgrowth active sites on the laminin alpha4 chain G domain.

The laminin alpha4 chain is widely distributed in various mesodermal tissues, including the perineurium of peripheral nerves, dorsal root ganglion (DRG), skeletal muscle, and capillaries, and plays important roles in synaptic specialization at the neuromuscular junction and in microvascular formation. The C-terminal globular domain (G domain) of the laminin alpha4 chain was previously found to be critical for heparin binding and cell attachment activity. Here, we focused on neurite outgrowth activity of the laminin alpha4 chain G domain. We found that the recombinant alpha4 chain G domain protein (rec-alpha4G) promoted neurite outgrowth of rat pheochromocytoma PC12 cells. When 114 overlapping synthetic peptides that covered the entire G domain were tested for neurite outgrowth activity, nine peptides were active, but the 105 remaining peptides did not exhibit activity. Three of the nine active peptides, A4G6 (LAIKNDNLVYVY), A4G20 (DVISLYNFKHIY), and A4G107 (VIRDSNVVQLDV), strongly promoted neurite outgrowth of PC12 cells. A4G107 was found to form amyloid-like fibrils in Congo red, X-ray, and electron microscopy analyses. We also synthesized cyclic peptides to evaluate their conformational requirements. Cyclic peptide A4G82X (cyc-A4G82X;TLFLAHGRLVFX, where X is norleucine) significantly enhanced neurite outgrowth activity, but the rest of the cyclic peptides eliminated the activity. The A4G82 sequence is located on the loop region, suggesting that the activity of A4G82 is required for a loop conformation. These peptides also exhibited neurite outgrowth activity with dorsal root ganglion (DRG) explants and with DRG cells from E14.5 mouse embryos, indicating that they are active in both neuronal cell lines and native neuronal cells. Taken together, the data suggest that the peptides from the laminin alpha4 chain G domain promote neurite outgrowth activity via a specific conformation.

Proactive transplantation of human neural stem cells prevents degeneration of striatal neurons in a rat model of Huntington disease.

We have investigated the effectiveness of transplantation of human neural stem cells into adult rat striatum prior to induction of striatal damage with the mitochondrial toxin 3-nitropropionic acid (3-NP). Systemic 3-NP administration caused widespread neuropathological deficits similar to ones found in Huntington disease (HD) including impairment in motor function (rotarod balance test) and extensive degeneration of neuron-specific nuclear antigen (NeuN)(+) neurons, calbindin(+) neurons and glutamic acid decarboxylase (GAD)(+) striatal neurons. Animals receiving intrastriatal implantation of human neural stem cells (hNSCs) 1 week before 3-NP treatments exhibited significantly improved motor performance and reduced damage to striatal neurons compared with control sham injections. In contrast, transplantation of hNSCs at 12 h after the initial 3-NP administration did not lead to any improvement in motor performance or protect striatal neurons from the 3-NP-induced toxicity. These results indicate that the presence of grafted hNSCs before 3-NP treatment is required for host striatal neuronal protection and enhanced motor function. Immunoreactivity of brain-derived neurotrophic factor (BDNF) was found in vitro in cultured hNSCs and in vivo in grafted NSCs with expression and secretion of BDNF demonstrated by RT-PCR, immunocytochemistry, dot-blot, and ELISA analyses. Thus, protective effects of proactive transplantation of hNSCs may be due, in part, to effects mediated by BDNF. The findings in this work have particular relevance to a rat model of HD in that proactive transplanted hNSCs protect host striatal neurons against neuronal injury and improve motor impairment induced by 3-NP toxicity.

Adenosine triphosphate induces proliferation of human neural stem cells: Role of calcium and p70 ribosomal protein S6 kinase.

Human neural stem cells (NSCs) grown in culture responded to extracellularly applied adenosine triphosphate (ATP), and the rate of proliferation increased as shown by immunocytochemical and RT-PCR analysis. Activation of P2 purinoceptors by ATP is coupled to the release of intracellular calcium ([Ca(2+)](i)) from thapsigargin-sensitive intracellular stores. ATP-induced proliferation was blocked by thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase. Neither EGTA, a calcium chelator, nor caffeine had any effect on ATP-induced [Ca(2+)](i) increases. Multiblot kinase analysis, by which activation of 24 different kinases could be determined, showed that application of ATP to NSCs predominantly activated p70 ribosomal protein S6 kinase (p70 S6 kinase). As well, rapamycin, a p70 S6 kinase inhibitor, blocked the ATP-mediated proliferative response in NSCs. After outlining a role for p70 S6 kinase in ATP-mediated NSC proliferation, we examined the possibility that phosphatidylinositol 3-kinase (PI3-kinase) acts upstream of p70 S6 kinase. The application of wortmannin, a PI3-kinase inhibitor, decreased both ATP-mediated p70 S6 kinase activation and NSC proliferation. From these results, we conclude that ATP application to NSCs induces release of Ca(2+) from intracellular Ca(2+) stores and that this increase in intracellular Ca(2+) in turn promotes NSC proliferation. The increase in NSC proliferation observed following ATP application can also be mediated by PI3-kinase-dependent p70 S6 kinase activation.

Fractalkine and fractalkine receptors in human neurons and glial cells.

Fractalkine has been identified as a novel chemokine that exhibits cell adhesion and chemoattractive properties in the central nervous system (CNS), and the fractalkine receptors, CX3CR1, are also expressed in the CNS. In the present study, the expression of fractalkine and fractalkine receptors was investigated in enriched populations of human CNS neurons, astrocytes, and microglia. In addition, the regulatory role played by protein kinase C (PKC) in fractalkine secretion in neurons was determined in A1 human hybrid neuronal cell line produced between a human cerebral neuron and a human neuroblastoma cell. Human neurons and astrocytes expressed fractalkine mRNA as determined by the revserse transcriptase-polymerase chain reaction (RT-PCR) analysis, while human microglia preparation did not express the fractalkine message. Human neurons and microglia expressed CX3CR1 mRNA, but astrocytes did not. These results suggest that fractalkine secreted by CNS neurons and astrocytes produce biological effects in neurons and microglia. Although phorbol ester did not change the expression of fractalkine mRNA level in A1 hybrid neurons, it did upregulate fractalkine secretion over unstimulated controls. This upregulation of fractalkine production was suppressed by the treatment with Ro32-0432, a PKC inhibitor. These results indicate that intracellular signals transduced by PKC play an important role in the regulation of soluble fractalkine at the post-transcriptional level in human neurons. As for the biological function of fractalkine, extracellularly applied fractalkine increased the number of bromodeoxyuridine-labeled microglia 3-fold over the untreated controls, indicating fractalkine induces proliferation of human microglia. These observations suggest that fractalkine released by injured neurons could induce proliferation, activation and/or migration of microglia at the injured brain sites.