Contribution of propriospinal neurons to recovery of hand dexterity after corticospinal tract lesions in monkeys.

The direct cortico-motoneuronal connection is believed to be essential for the control of dexterous hand movements, such as precision grip in primates. It was reported, however, that even after lesion of the corticospinal tract (CST) at the C4-C5 segment, precision grip largely recovered within 1-3 mo, suggesting that the recovery depends on transmission through intercalated neurons rostral to the lesion, such as the propriospinal neurons (PNs) in the midcervical segments. To obtain direct evidence for the contribution of PNs to recovery after CST lesion, we applied a pathway-selective and reversible blocking method using double viral vectors to the PNs in six monkeys after CST lesions at C4-C5. In four monkeys that showed nearly full or partial recovery, transient blockade of PN transmission after recovery caused partial impairment of precision grip. In the other two monkeys, CST lesions were made under continuous blockade of PN transmission that outlasted the entire period of postoperative observation (3-4.5 mo). In these monkeys, precision grip recovery was not achieved. These results provide evidence for causal contribution of the PNs to recovery of hand dexterity after CST lesions; PN transmission is necessary for promoting the initial stage recovery; however, their contribution is only partial once the recovery is achieved.

Genetic dissection of the circuit for hand dexterity in primates.

It is generally accepted that the direct connection from the motor cortex to spinal motor neurons is responsible for dexterous hand movements in primates. However, the role of the 'phylogenetically older' indirect pathways from the motor cortex to motor neurons, mediated by spinal interneurons, remains elusive. Here we used a novel double-infection technique to interrupt the transmission through the propriospinal neurons (PNs), which act as a relay of the indirect pathway in macaque monkeys (Macaca fuscata and Macaca mulatta). The PNs were double infected by injection of a highly efficient retrograde gene-transfer vector into their target area and subsequent injection of adeno-associated viral vector at the location of cell somata. This method enabled reversible expression of green fluorescent protein (GFP)-tagged tetanus neurotoxin, thereby permitting the selective and temporal blockade of the motor cortex­PN­motor neuron pathway. This treatment impaired reach and grasp movements, revealing a critical role for the PN-mediated pathway in the control of hand dexterity. Anti-GFP immunohistochemistry visualized the cell bodies and axonal trajectories of the blocked PNs, which confirmed their anatomical connection to motor neurons. This pathway-selective and reversible technique for blocking neural transmission does not depend on cell-specific promoters or transgenic techniques, and is a new and powerful tool for functional dissection in system-level neuroscience studies.

DNA methylation and methyl-binding proteins control differential gene expression in distinct cortical areas of macaque monkey.

Distinct anatomical regions of the neocortex subserve different sensory modalities and neuronal integration functions, but mechanisms for these regional specializations remain elusive. Involvement of epigenetic mechanisms for such specialization through the spatiotemporal regulation of gene expression is an intriguing possibility. Here we examined whether epigenetic mechanisms might play a role in the selective gene expression in the association areas (AAs) and the primary visual cortex (V1) in macaque neocortex. By analyzing the two types of area-selective gene promoters that we previously identified, we found a striking difference of DNA methylation between these promoters, i.e., hypermethylation in AA-selective gene promoters and hypomethylation in V1-selective ones. Methylation levels of promoters of each area-selective gene showed no areal difference, but a specific methyl-binding protein (MBD4) was enriched in the AAs, in correspondence with expression patterns of AA-selective genes. MBD4 expression was mainly observed in neurons. MBD4 specifically bound to and activated the AA-selective genes both in vitro and in vivo. Our results demonstrate that methylation in the promoters and specific methyl-binding proteins play an important role in the area-selective gene expression profiles in the primate neocortex.

Health Status Progression Measured Using Weekly Telemonitoring of COPD Assessment Test Scores Over 1 Year and Its Association With COPD Exacerbations.

Background: A previous longitudinal study of chronic obstructive pulmonary disease (COPD) Assessment Test (CAT) score changes suggested patients fall into 3 patterns: stable, improving, and worsening. This study assessed the evolution of CAT scores over time and its relationship to exacerbations. Methods: In total, 84 participants used a telemedicine platform to complete CAT weekly for 52 weeks. Completion rates, annualized change in CAT scores, and learning effects were measured, as well as CAT changes of >4 units during look-back periods of 4 and 8 weeks. In a subgroup of participants with at least a 25% completion rate (adherent group, n=68 [81%]), the relationship between change in CAT score and exacerbations at any time during the study was examined post hoc. Results: Linear regression showed that 50%, 22%, and 28% of the adherent subgroup had CAT scores indicating worsening, stable, and improving health status, respectively. In the adherent subgroup, 70% (n=7/10) of participants who had an exacerbation during the study had worsening CAT scores, versus 47% (n=27/58) without an exacerbation. The hazard ratio association between CAT score increase and moderate exacerbation was 1.13 (95% confidence interval: 1.03-1.24). Most participants experienced at least one CAT score change of >4 units, and 7% showed an initial learning effect with a median of 2 weeks. Conclusion: Measuring trends in CAT scores may allow future studies to group patients into 3 defined categories of change over time and quantify CAT change trajectories to assess treatment response and potentially predict medium-term outcomes within individual patients.

Efficacy and safety of indacaterol 150 and 300 µg in chronic obstructive pulmonary disease patients from six Asian areas including Japan: a 12-week, placebo-controlled study.

BACKGROUND AND OBJECTIVE: The efficacy and safety of indacaterol, a novel inhaled once daily ultra long-acting ß(2) -agonist was evaluated in COPD patients in six Asian countries/areas. This study was primarily designed to obtain the regulatory approval of indacaterol in Japan. METHODS: Moderate-to-severe COPD patients were randomized to indacaterol 150 µg, indacaterol 300 µg or placebo once daily. Efficacy variables: trough FEV(1) (average of 23 h 10 min and 23 h 45 min post-dose values), health status (St. George's Respiratory Questionnaire) and transition dyspnoea index at week 12. Safety/tolerability was evaluated. RESULTS: A total of 347 patients were randomized (96.5% male, mean (SD) age 66.7 (8.38) years, post-bronchodilator FEV(1) % predicted: 53.7 (12.50)); 88.8% completed. The least squares means (LSM) trough FEV(1) at week 12 for indacaterol 150 µg, indacaterol 300 µg and placebo were 1.34 L, 1.37 L and 1.17 L, respectively, with differences versus placebo exceeding the prespecified minimal clinically important difference of 0.12 L (0.17 L and 0.20 L for indacaterol 150 µg and 300 µg, respectively, both P < 0.001). The week 12 LSM transition dyspnoea index score was statistically superior for both indacaterol doses versus placebo (differences of 1.30 and 1.26, P < 0.001; both exceeding the minimal clinically important difference of 1). At week 12, both indacaterol doses provided statistically significant (P ≤ 0.005) and clinically meaningful (≥4 units) improvements in LSM St. George's Respiratory Questionnaire total score versus placebo (differences: -4.8 and -5.7 units). Adverse events for indacaterol (49.1%, both doses) were lower than placebo (59.0%) and were mostly mild/moderate in severity; no deaths were reported. CONCLUSIONS: Indacaterol provided clinically significant bronchodilation and improvements in dyspnoea and health status in Asian COPD patients.

[Difficult ventilation after sugammadex administration: a case report].

A 71-year-old woman was scheduled for arthroscopic knee surgery. Anesthesia was administered with sevoflurane, fentanyl, and rocuronium bromide. Total dose of fentanyl was 200 microg and total dose of rocuronium bromide was 40mg. After surgery sugammadex 150 mg was given before awakening of the patient and appearance of spontaneous breathing. Immediately after the administration of sugammadex airway pressure increased to 37 cmH20, and ventilation became difficult. After naloxone 0.1 mg injection, ventilation improved dramatically. The cause of difficult ventilation was surmised to be upper airway reflex or muscle rigidity caused by reaction to fentanyl. We thought the phenomenon was clearly manifested by rapid recovery from muscle relaxation by injection of sugammadex. Before injection of sugammadex, it is necessary to confirm the effects of anesthetics on the patient's condition.

Phylogenetic view of the compensatory mechanisms in motor and sensory systems after neuronal injury.

Through phylogeny, novel neural circuits are added on top of ancient circuits. Upon injury of a novel circuit which enabled fine control, the ancient circuits can sometimes take over its function for recovery; however, the recovered function is limited according to the capacity of the ancient circuits. In this review, we discuss two examples of functional recovery after neural injury in nonhuman primate models. The first is the recovery of dexterous hand movements following damage to the corticospinal tract. The second is the recovery of visual function after injury to the primary visual cortex (V1). In the former case, the functions of the direct cortico-motoneuronal pathway, which specifically developed in higher primates for the control of fractionated digit movements, can be partly compensated for by other descending motor pathways mediated by rubrospinal, reticulospinal, and propriospinal neurons. However, the extent of recovery depends on the location of the damage and which motor systems take over its function. In the latter case, after damage to V1, which is highly developed in primates, either the direct pathway from the lateral geniculate nucleus to extrastriate visual cortices or that from the midbrain superior colliculus-pulvinar-extrastriate/parietal cortices partly takes over the function of V1. However, the state of visual awareness is no longer the same as in the intact state, which might reflect the limited capacity of the compensatory pathways in visual recognition. Such information is valuable for determining the targets of neuromodulatory therapies and setting treatment goals after brain and spinal cord injuries.

A Telemedicine Approach for Monitoring COPD: A Prospective Feasibility and Acceptability Cohort Study.

Background: Telemedicine may help the detection of symptom worsening in patients with chronic obstructive pulmonary disease (COPD), potentially resulting in improved outcomes. This study aimed to determine the feasibility and acceptability of telemedicine among patients with COPD and physicians and facility staff in Japan. Methods: This was a 52-week multicenter, prospective, single-arm, feasibility and acceptability cohort study of Japanese patients ≥40 years of age with COPD or asthma-COPD overlap. Participants underwent training to use YaDoc, a telemedicine smartphone App, which included seven daily symptom questions and weekly COPD Assessment Test (CAT) questions. The primary endpoint was participant compliance for required question completion. The secondary endpoint was participant and physician/facility staff acceptability of YaDoc based on questionnaires completed at Week 52. The impact of the Japanese COVID-19 pandemic state of emergency on results was also assessed. Results: Of the 84 participants enrolled (mean age: 68.7 years, 88% male), 72 participants completed the study. Completion was high in the first six months but fell after that. Median (interquartile range [IQR]) compliance for daily questionnaire entry was 66.6% (31.0-91.8) and 81.0% (45.3-94.3) for weekly CAT entry. Positive participant responses to the exit questionnaire were highest regarding YaDoc ease of use (83.8%), positive impact on managing health (58.8%), and overall satisfaction (53.8%). Of the 26 physicians and facility staff enrolled, 24 completed the study. Of these, the majority (66.7%) responded positively regarding app facilitation of communication between physicians and participants to manage disease. Compliance was similar before and after the first COVID-19 state of emergency in Japan. Conclusion: Daily telemedicine monitoring is potentially feasible and acceptable to both patients and physicians in the management of COPD. These results may inform potential use of telemedicine in clinical practice and design of future studies. Clinical Trial Registration: JapicCTI-194916.

Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

In patients with damage to the primary visual cortex (V1), residual vision can guide goal-directed movements to targets in the blind field without awareness. This phenomenon has been termed blindsight, and its neural mechanisms are controversial. There should be visual pathways to the higher visual cortices bypassing V1, however some literature propose that the signal is mediated by the superior colliculus (SC) and pulvinar, while others claim the dorsal lateral geniculate nucleus (dLGN) transmits the signal. Here, we directly test the role of SC to ventrolateral pulvinar (vlPul) pathway in blindsight monkeys. Pharmacological inactivation of vlPul impairs visually guided saccades (VGS) in the blind field. Selective and reversible blockade of the SC-vlPul pathway by combining two viral vectors also impairs VGS. With these results we claim the SC-vlPul pathway contributes to blindsight. The discrepancy would be due to the extent of retrograde degeneration of dLGN and task used for assessment.

Imidafenacin, An Orally Active Muscarinic Receptor Antagonist, Improves Pulmonary Function In Patients With Chronic Obstructive Pulmonary Disease: A Multicenter, Randomized, Double-Blind, Placebo-Controlled 3×3 Crossover Phase II Trial.

Background: Although long-acting muscarinic receptor antagonists are central to the management of chronic obstructive pulmonary disease (COPD), inhaled medicines may have technical difficulty in some patients and adherence barriers. Methods: A multicenter, randomized, double-blind, placebo-controlled 3×3 crossover Phase II trial was performed to evaluate the efficacy and safety of oral administration of the antimuscarinic agent imidafenacin in patients with COPD. Twenty-seven male COPD patients with % forced expiratory volume in 1 s (FEV1) ≥30% and <80% predicted were randomized to single oral dose of imidafenacin 0.1 mg, imidafenacin 0.2 mg, or placebo. Results: Maximum change in FEV1 with both doses of imidafenacin significantly improved from baseline to 24 hrs after administration when compared with a placebo. Area under the curve in FEV1 during 24 hrs after administration with 0.2 mg, but not 0.1 mg dose, was significantly improved when compared with a placebo, and the improvement was significantly based on dose-dependent manners. Plasma imidafenacin level was positively correlated with change in FEV1. All subjects with both doses of imidafenacin completed without moderate nor severe adverse events. Conclusion: A single oral dose of imidafenacin 0.1 mg or imidafenacin 0.2 mg may contribute to the improvement of pulmonary function with excellent safety and tolerability in patients with COPD. Trial registration: JapicCTI-121760 (Japan Pharmaceutical Information Center - Clinical Trials Information [JapicCTI]; http://www.clinicaltrials.jp/user/cteSearch_e.jsp).

Medium- to long-term survival and functional examination of human iPSC-derived retinas in rat and primate models of retinal degeneration.

BACKGROUND: We have previously reported that xeno-transplanted human ESC-derived retinas are able to mature in the immunodeficient retinal degeneration rodent models, similar to allo-transplantations using mouse iPSC-derived retina. The photoreceptors in the latter developed outer segments and formed synapses with host bipolar cells, driving light responses of host retinal ganglion cells. In view of clinical application, here we further confirmed the competency of human iPSC-derived retina (hiPSC-retina) to mature in the degenerated retinas of rat and monkey models. METHODS: Human iPSC-retinas were transplanted in rhodopsin mutant SD-Foxn1 Tg(S334ter)3LavRrrc nude rats and two monkeys with laser-induced photoreceptor degeneration. Graft maturation was studied by immunohistochemistry and its function was examined by multi-electrode array (MEA) recording in rat retinas and visually-guided saccade (VGS) in a monkey. FINDINGS: A substantial amount of mature photoreceptors in hiPSC-retina graft survived well in the host retinas for at least 5 months (rat) to over 2 years (monkey). In 4 of 7 transplanted rat retinas, RGC light responses were detected at the grafted area. A mild recovery of light perception was also suggested by the VGS performance 1.5 years after transplantation in that monkey. INTERPRETATION: Our results support the competency of hiPSC-derived retinas to be clinically applied for transplantation therapy in retinal degeneration, although the light responses observed in the present models were not conclusively distinguishable from residual functions of degenerating host retinas. The functional analysis may be further elaborated using other models with more advanced retinal degeneration.

Validation of symptom-based COPD questionnaires in Japanese subjects.

BACKGROUND AND OBJECTIVE: Symptom-based questionnaires may be helpful in diagnosing patients with COPD. The aim of this study was to determine whether two COPD questionnaires designed in Western countries were applicable to Japanese and other Asian patients. METHODS: The participants were Japanese people aged 40 years and over. Each subject answered questions on demographics and symptoms and underwent spirometry before and after administration of a bronchodilator. Questionnaire A was designed to identify previously undiagnosed COPD and questionnaire B was designed to differentiate between COPD and asthma. RESULTS: The numbers of COPD patients who answered questionnaires A and B were 33 of 169 (19.5%) and 112 of 168 (66.7%), respectively. Comparison of the COPD group with the non-COPD group revealed a significant difference in total score in both questionnaire A and questionnaire B (both P < 0.001). The area under the receiver operating characteristic curve (AUC-ROC) for questionnaire A was 0.791. With a cut-off value of 16.5 points, the sensitivity and specificity were 0.939 and 0.404, and with a 19.5-point cut-off, sensitivity and specificity were 0.848 and 0.647, respectively. The AUC-ROC for questionnaire B was 0.765. With cut-off values of 18.5 and 24.5 points, the respective sensitivities and specificities were 0.946 and 0.393, and 0.741 and 0.607. CONCLUSIONS: A simple self-administered questionnaire can help to diagnose COPD in Japanese subjects. When these questionnaires are used in Japan, cut-off values should be set somewhat higher than in Western countries.

High Detection Rates of Urine Mycobacterium tuberculosis in Patients with Suspected Miliary Tuberculosis.

Objective The utility of detecting Mycobacterium tuberculosis in urine samples from patients with pulmonary tuberculous with diffuse small nodular shadows (suspected miliary tuberculosis (MTB)) is still unclear in Japan. A retrospective cross-sectional study was conducted to investigate the detection rates of M. tuberculosis in urine of patients with suspected MTB. Methods Among 687 hospitalized patients with tuberculosis, 45 with culture-confirmed suspected MTB and the data of culture and polymerase chain reaction (PCR) for M. tuberculosis in urine and sputum samples were investigated. The detection rates of M. tuberculosis in urine using cultures and PCR were calculated. The detection rate of urine was then compared with that of bone marrow aspiration. Results Fourteen patients with suspected MTB were ultimately analyzed. A diagnosis of miliary tuberculosis was suspected in all patients before anti-tuberculosis chemotherapy. Positive results by PCR (11 [78.6%] cases) and culture (8 [57.1%]) were obtained from urine samples. In patients with suspected MTB, there was no significant difference in the detection rates between M. tuberculosis in urine using a combination of PCR and culture (85.6% [12/14 cases]) and bone marrow aspiration (66.7% [8/12 cases]) (p>0.05). Conclusion Using PCR and culture, we demonstrated high detection rates of M. tuberculosis in the urine of patients with suspected MTB. A combination of PCR and culture compared favorably with the detection rates achieved with bone marrow aspiration. We believe that detection of M. tuberculosis from urine and sputum samples may be easy and safe for patients with disseminated tuberculosis infections such as definitive MTB.

[A case of follicular bronchiolitis preceding rheumatoid arthritis].

A 52-year-old woman was admitted to Yame General Hospital because of persistent cough, wheeze, and shortness of breath at age 48. Chest X-ray and computed tomography (CT) showed bilateral centrilobular shadows. Pulmonary function test revealed obstructive dysfunction. She also had chronic sinusitis. Initially, diffuse panbronchiolitis was diagnosed and she was given macrolides, but no improvement was observed. Thus video-assisted thoracoscopic lung biopsy (VATS) was performed in order to establish a definitive diagnosis. Histopathological findings were compatible with a diagnosis of follicular bronchiolitis. Treatment with corticosteroid (oral prednisolone, 50 mg/day) improved her condition. However, on reducing the steroid doze, her symptoms and chest X-ray film/CT findings became exacerbated. In addition, polyarthritis appeared. Further investigations revealed a diagnosis of rheumatoid arthritis. Only 2 cases of follicular bronchiolitis preceding rheumatoid arthritis have been reported in Japan.

Comparative analyses of adeno-associated viral vector serotypes 1, 2, 5, 8 and 9 in marmoset, mouse and macaque cerebral cortex.

Here we investigated the transduction characteristics of adeno-associated viral vector (AAV) serotypes 1, 2, 5, 8 and 9 in the marmoset cerebral cortex. Using three constructs that each has hrGFP under ubiquitous (CMV), or neuron-specific (CaMKII and Synapsin I (SynI)) promoters, we investigated (1) the extent of viral spread, (2) cell type tropism, and (3) neuronal transduction efficiency of each serotype. AAV2 was clearly distinct from other serotypes in small spreading and neuronal tropism. We did not observe significant differences in viral spread among other serotypes. Regarding the cell tropism, AAV1, 5, 8 and 9 exhibited mostly glial expression for CMV construct. However, when the CaMKII construct was tested, cortical neurons were efficiently transduced (>∼70% in layer 3) by all serotypes, suggesting that glial expression obscured neuronal expression for CMV construct. For both SynI and CaMKII constructs, we observed generally high-level expression in large pyramidal cells especially in layer 5, as well as in parvalbumin-positive interneurons. The expression from the CaMKII construct was more uniformly observed in excitatory cells compared with SynI construct. Injection of the same viral preparations in mouse and macaque cortex resulted in essentially the same result with some species-specific differences.

Neural responses in the primary visual cortex of the monkey during perceptual filling-in at the blind spot.

The phenomenon of perceptual filling-in demonstrates that physical stimuli presented on the retina do not necessarily correspond to surface perception, and that our visual system has mechanisms with which to interpolate missing information in order to construct continuous surfaces. Among its various forms, filling-in at the blind spot is one of the most remarkable. To study the neural mechanisms involved in filling-in at the blind spot, we recently conducted a recording experiment aimed at determining whether the neurons in the primary visual cortex (V1) that represent the visual field corresponding to the blind spot are activated when filling-in occurs. We found that neurons located in deep layers of the V1, particularly layer 6, respond to large stimuli that cover the blind spot and induce perceptual filling-in. These neurons tended to have very large receptive fields, which extended out of the blind spot, and preferred relatively large stimuli. We believe that neurons in the V1 region representing the blind spot encode information essential for perceptual filling-in at the blind spot.

[A case of allergic granulomatosis and angiitis without symptoms of asthma].

We present a case of allergic rhinitis in a 68-year-old woman in whom eosinophilia was found when she complained of common cold-like symptoms. The patient noticed a mass lesion on her left neck, which improved with antibiotic treatment, but her coughing continued and edema of both lower extremities appeared. She was admitted to our hospital, because of abnormalities in her electrocardiogram and cardiomegaly seen in a chest radiograph. The discomfort due to the edema in the soles of both feet remained even after steroid therapy. Her chest radiograph revealed ground-glass opacity, and a transbronchial lung biopsy revealed granulation tissue with the infiltration of eosinophils into the interstitium. Allergic granulomatosis angiitis was diagnosed because of granulomatosis vasculitis resulting from sural nerve biopsy. This was a rare case of allergic granulomatosis angiitis because her lung function was normal, she had no history of bronchial asthma, and there were no clear symptoms of bronchial asthma.

[Pulmonary tuberculosis mimicking fungus ball].

We treated a 42-year-old man with pulmonary tuberculosis presenting as a round mass in a cavitary lesion that resembled a fungus ball. These findings appeared within a short time. The diagnosis was confirmed by isolation of Mycobacterium tuberculosis from his sputum. He also had diabetes mellitus that was poorly controlled. The patient was treated with antituberculous chemotherapy and insulin therapy. With these treatments, the roentgenographic abnormalities resolved fairly rapidly.

Role of Direct vs. Indirect Pathways from the Motor Cortex to Spinal Motoneurons in the Control of Hand Dexterity.

Evolutionally, development of the direct connection from the motor cortex to spinal motoneurons [corticomotoneuronal (CM) pathway] parallels the ability of hand dexterity. Damage to the corticofugal fibers in higher primates resulted in deficit of fractionated digit movements. Based on such observations, it was generally believed that the CM pathway plays a critical role in the control of hand dexterity. On the other hand, a number of "phylogenetically older" indirect pathways from the motor cortex to motoneurons still exist in primates. The indirect pathways are mediated by intercalated neurons such as segmental interneurons (sINs), propriospinal neurons (PNs) reticulospinal neurons (RSNs), or rubrospinal neurons (RuSNs). However, their contribution to hand dexterity remains elusive. Lesion of the brainstem pyramid sparing the transmission through the RuSNs and RSNs, resulted in permanent deficit of fractionated digit movements in macaque monkeys. On the other hand, in our recent study, after lesion of the dorsolateral funiculus (DLF) at the C5 segment, which removed the lateral corticospinal tract (l-CST) including the CM pathway and the transmission through sINs and RuSNs but spared the processing through the PNs and RSNs, fractionated digit movements recovered within several weeks. These results suggest that the PNs can be involved in the recovery of fractionated digit movements, but the RSNs and RuSNs have less capacity in this regard. However, on closer inspection, it was found that the activation pattern of hand and arm muscles considerably changed after the C5 lesion, suggesting limitation of PNs for the compensation of hand dexterity. Altogether, it is suggested that PNs, RSNs RuSNs, and the CM pathway (plus sINs) make a different contribution to the hand dexterity and appearance of motor deficit of the hand dexterity caused by damage to the corticofugal fibers and potential of recovery varies depending on the rostrocaudal level of the lesion.

Viral vector-mediated selective and reversible blockade of the pathway for visual orienting in mice.

Recently, by using a combination of two viral vectors, we developed a technique for pathway-selective and reversible synaptic transmission blockade, and successfully induced a behavioral deficit of dexterous hand movements in macaque monkeys by affecting a population of spinal interneurons. To explore the capacity of this technique to work in other pathways and species, and to obtain fundamental methodological information, we tried to block the crossed tecto-reticular pathway, which is known to control orienting responses to visual targets, in mice. A neuron-specific retrograde gene transfer vector with the gene encoding enhanced tetanus neurotoxin (eTeNT) tagged with enhanced green fluorescent protein (EGFP) under the control of a tetracycline responsive element was injected into the left medial pontine reticular formation. 7-17 days later, an adeno-associated viral vector with a highly efficient Tet-ON sequence, rtTAV16, was injected into the right superior colliculus. 5-9 weeks later, the daily administration of doxycycline (Dox) was initiated. Visual orienting responses toward the left side were impaired 1-4 days after Dox administration. Anti-GFP immunohistochemistry revealed that a number of neurons in the intermediate and deep layers of the right superior colliculus were positively stained, indicating eTeNT expression. After the termination of Dox administration, the anti-GFP staining returned to the baseline level within 28 days. A second round of Dox administration, starting from 28 days after the termination of the first Dox administration, resulted in the reappearance of the behavioral impairment. These findings showed that pathway-selective and reversible blockade of synaptic transmission also causes behavioral effects in rodents, and that the crossed tecto-reticular pathway clearly controls visual orienting behaviors.