Effects and safety of high-frequency rTMS in subacute ischemic stroke patients.

OBJECTIVE: Although high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) has shown benefits in chronic stroke, its application in subacute ischemic stroke remains underexplored. This study aims to investigate the effects and safety of lesion-side HF-rTMS in subacute ischemic stroke. METHODS: Prospective lesion-side HF-rTMS was conducted on consecutive ischemic stroke patients within 3 days of onset from February 2019 to June 2022. Inclusion criteria required persistent paralysis (NIHSS score ≥ 1 for at least 7 days). Exclusion criteria comprised cortical infarction, disturbance of consciousness, and age over 80 years. A conventional rehabilitation group meeting the same criteria from June 2015 to January 2019 served as a comparison. We compared the two groups regarding clinical background and outcome. We also evaluated incidence of epilepsy and exacerbation of the NIHSS score in the rTMS group. RESULTS: Seventy-eight patients participated, with 50% in the HF-rTMS group. Median time from onset to HF-rTMS initiation was 9 (IQR 7-12) days. A favorable outcome (modified Rankin Scale score 0-2) at 3 months was more frequent in the rTMS group (80% vs. 44%, p = 0.002). HF-rTMS was independently associated with a favorable outcome at 3 months (OR = 5.60, 95% CI = 1.53-20.50, p = 0.009). No cases of epilepsy or exacerbation of NIHSS score were observed. CONCLUSIONS: HF-rTMS demonstrates potential effectiveness and safety in subacute ischemic stroke patients.

Focal brain cooling suppresses spreading depolarization and reduces endothelial nitric oxide synthase expression in rats.

This study aimed to investigate the effects of focal brain cooling (FBC) on spreading depolarization (SD), which is associated with several neurological disorders. Although it has been studied from various aspects, no medication has been developed that can effectively control SD. As FBC can reduce neuronal damage and promote functional recovery in pathological conditions such as epilepsy, cerebral ischemia, and traumatic brain injury, it may also potentially suppress the onset and progression of SD. We created an experimental rat model of SD by administering 1 M potassium chloride (KCl) to the cortical surface. Changes in neuronal and vascular modalities were evaluated using multimodal recording, which simultaneously recorded brain temperature (BrT), wide range electrocorticogram, and two-dimensional cerebral blood flow. The rats were divided into two groups (cooling [CL] and non-cooling [NC]). Warm or cold saline was perfused on the surface of one hemisphere to maintain BrT at 37°C or 15°C in the NC and CL groups, respectively. Western blot analysis was performed to determine the effects of FBC on endothelial nitric oxide synthase (eNOS) expression. In the NC group, KCl administration triggered repetitive SDs (mean frequency = 11.57/h). In the CL group, FBC increased the duration of all KCl-induced events and gradually reduced their frequency. Additionally, eNOS expression decreased in the cooled brain regions compared to the non-cooled contralateral hemisphere. The results obtained by multimodal recording suggest that FBC suppresses SD and decreases eNOS expression. This study may contribute to developing new treatments for SD and related neurological disorders.

Thin aortic arch plaque is associated with the development of atrial fibrillation for embolic stroke of undetermined source in patients with an insertable cardiac monitor.

BACKGROUND AND OBJECTIVE: This study's objective is to investigate whether mild aortic arch plaque is associated with the development of atrial fibrillation (AF) in stroke patients with embolic stroke of undetermined source (ESUS) during the first year following the implantation of an insertable cardiac monitor (ICM). METHODS: The participants in this cross-sectional observational study were consecutive patients with ESUS, even after transesophageal echocardiography. We assessed the relationship between the thickness of the participants' aortic arch plaque and AF detected after ICM implantation. RESULTS: Of the 50 consecutive patients with ESUS enrolled in this study, 12 (24%) developed AF. We observed that thicker aortic arch plaque was associated with undetected AF (2.3 mm vs. 1.2 mm, p < 0.001). Aortic arch plaque thickness was independent associated with undetected AF (OR 54.00, 95% CI 2.706-1077.544, p = 0.009). When the cut-off value for aortic arch plaque thickness was 1.8 mm, the sensitivity and specificity were 71.1% and 91.7%, respectively (95% CI = 0.75-0.98, p < 0.001). Also, patients having both aortic arch plaque with a thickness < 1.8 mm and a CHADS2 score ≥ 4 were more likely to have detectable AF than no AF (88% vs. 12%, p < 0.001). CONCLUSION: A thinner aortic arch plaque was associated with the development of AF. Patients with mild aortic plaques below 4 mm but ≥1.8 mm in thickness and without other high-risk features are less likely to have paroxysmal AF on ICM, and these plaques may be a possible source of embolism for their strokes.

Urinary Immunoglobulin G Is a Novel Biomarker for Atherosclerotic Burden in Mild Acute Ischemic Stroke Patients.

AIMS: Urinary immunoglobulin G (IgG) may be a stronger marker of atherosclerosis than microalbuminuria are because urinary IgG reflects proteinuria level and size-selectivity loss. Microalbuminuria-not urinary IgG-is associated with mild acute ischemic stroke (MAIS). METHODS: Using the Jikei University School of Medicine Stroke Registry, we selected and screened patients with symptomatic acute ischemic stroke (onset-to-door time ≤ 24 h). The exclusion criteria were (1) on-admission NIHSS scores ＞10, (2) a modified Rankin Scale (mRS) score ≥ 2 prior to stroke onset, (3) incomplete data (no urinalysis ≤ 3 days after admission or no mRS score at 90 days from stroke onset), and (4) an active malignancy. Patients at 90 days post-discharge were divided into those with favorable mRS scores of 0-1 and those with unfavorable mRS scores of 2-6. Clinical backgrounds were compared for (1) patients with positive and negative urinary IgG results, and (2) patients with favorable and unfavorable outcomes. RESULTS: Of our study's 210 patients (164=male, median age=68, median eGFR=53.2 ml/min/1.73 m2), 30 (14%) presented with positive urinary IgG, which was associated with cardiovascular risk factors. Higher BNP, higher D-dimer, lower eGFR, and higher CAVI were associated with higher positive urinary IgG. The favorable group, comprising 155 (74%) patients, had higher negative urinary IgG than the unfavorable group (89% vs 76%, P=0.026). No statistical difference emerged regarding microalbuminuria (29% vs 29%, P=1.000). CONCLUSION: In MAIS, urinary IgG was associated with both the presence of atherosclerosis and an unfavorable outcome at 90 days after stroke onset.

Follow-Up Diffusion-Weighted Image Reveals Delayed Appearance of Ischemic Lesions in Suspected Transient Ischemic Attack.

INTRODUCTION: In patients suspected of transient ischemic attack (TIA), it is not uncommon to find no lesion on the diffusion-weighted image (DWI) on admission but a delayed appearance on the follow-up DWI. METHODS: Enrolled patients met the following criteria: (1) MRI performed within 24 hours of onset and seven days after admission; (2) National Institutes of Health Stroke Scale (NIHSS) score ≦4 on admission; (3) pre-stroke modified Rankin scale (mRS) score of 0-1. Patients were divided as follows: no lesion on the first DWI and a new lesion on the second DWI (delayed-specified ischemic stroke; DSIS); and no lesion on either the first or second DWI (well-screened TIA; WSTIA). We compared both groups regarding the clinical background and the outcome at three months. RESULTS: We identified 144 cases (male 70%; median age 64 years; DSIS, n=34) between October 2012 and March 2019. DSIS was older (71 vs. 60 years, p=0.006) and had a higher NIHSS score on admission (1 vs. 0, p=0.041), a higher rate of large vessel occlusion (LVO) (17% vs. 2%, p=0.008), and symptom duration over one hour (82% vs. 64%, p=0.041). A favorable outcome mRS score of 0-1 at three months was less frequent in DSIS (85% vs. 96%, p=0.004). Age/10 (OR 1.62, 95%CI 1.17-2.24; p=0.004) and LVO (OR 10.84, 95%CI 1.87-63.06; p=0.008) were independent factors for DSIS. CONCLUSIONS: In suspected TIA with age or LVO but no lesion in the initial DWI, the second DWI should be considered to identify the delayed appearance of an ischemic stroke.

Reduced Likelihood of Infarction in Crescendo Transient Ischemic Attack Caused by Vasculitic Middle Cerebral Artery Stenosis.

A 53-year-old woman was admitted to our hospital because of increasingly frequent transient speech disturbance and left upper limb weakness. Brain magnetic resonance imaging and angiography revealed multiple intracranial stenoses, including the proximal right middle cerebral artery (MCA), without evidence of infarction. The diagnosis of primary angiitis of the central nervous system was established based on circumferential vascular wall thickening with contrast enhancement observed in the right MCA. Following the administration of dual antiplatelet therapy and intravenous methylprednisolone pulse therapy, the patient experienced complete cessation of symptoms, and the stenosis gradually improved without infarction. The risk of infarct development in crescendo transient ischemic attacks may differ between inflammatory vascular stenosis and atherosclerosis.

Urinary Immunoglobulin G Is Associated with Deep and Infratentorial Cerebral Microbleeds in Stroke Patients.

BACKGROUND: Cerebral microbleeds (CMBs) detected on susceptibility-weighted imaging (SWI) are associated with cerebral small vessel disease. Chronic kidney disease and microalbuminuria have been associated with the presence of CMBs in stroke patients. Urinary immunoglobulin G (IgG) is measured to document glomerular injury; however, the relationship between urinary IgG and CMBs is unknown. METHODS: We retrospectively enrolled consecutive patients who had been admitted with transient ischemic attack (TIA) or ischemic stroke and identified those who had undergone SWI and a spot urine test. The location of CMBs was classified on magnetic resonance imaging as strictly lobar, deep/infratentorial (D/I), or mixed areas. We analyzed the association between urinary IgG and the presence and location of CMBs. RESULTS: We included 298 patients (86 female, median age 70 years, median eGFR 65.8 mL/min/1.73 m2). Positive urinary IgG and CMB results were found in 58 (19%) and 160 patients (54%), respectively. Urinary IgG positivity was significantly associated with CMBs compared with non-CMBs (28% vs. 9%, p < 0.001), and with D/I or mixed CMBs compared with non-D/I or mixed CMBs (34% vs. 10%, p < 0.001). Multivariate analysis revealed that urinary IgG and hypertension positivity were strongly associated with D/I or mixed CMBs (OR 3.479, 95% CI: 1.776-6.818, p < 0.001; OR 3.415, 95% CI: 1.863-6.258, p < 0.001). CONCLUSIONS: Urinary IgG was associated with the prevalence of D/I or mixed location CMBs in TIA or ischemic stroke patients. Our findings provide new insights into the association between urinary IgG and the distribution of CMBs.

Effects and safety of high-frequency rTMS in acute intracerebral hemorrhage patients: A pilot study.

OBJECTIVE: Although high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) in chronic intracerebral hemorrhage (ICH) is beneficial, it has been poorly investigated in rTMS for acute ICH. Our aim is to investigate the effects and safety of rTMS in acute spontaneous ICH. METHODS: We prospectively performed HF-rTMS on consecutive patients with ICH within 24 h from onset between April 2019 and August 2021. The inclusion criterion was (1) persistent paralysis, with an NIHSS scale of 1 or higher for at least 3 days after onset. The exclusion criteria were (1) cortical, subcortical, and cerebellar ICH, (2) disturbance of consciousness, and (3) over 80 years of age. For the purpose of comparison, we used a conventional rehabilitation group whose patients met the same criteria between April 2016 and March 2019. We evaluated incidence of epilepsy and exacerbation of the NIHSS score in the rTMS group. We also compared the two groups regarding clinical background and outcome. RESULTS: Enrolled in the study were a total of 44 patients. Of the patients, 22 (50%) were in the rTMS group. The median (IQR) time from onset to the start of rTMS was 9 (6-12) days. There were no cases of epilepsy or exacerbation of NIHSS after the start of rTMS. Favorable outcome (modified Rankin Scale score of between 0 and 2) at 3 months was frequently observed in the rTMS group (73% vs 27%, p = 0.006). HF-rTMS was independently associated with favorable outcome at 3 months (OR = 11.5, 95% CI = 2.194-60.447, p = 0.004). CONCLUSIONS: HF-rTMS may be safe and effective in acute ICH patients.

A critical period for learning and plastic changes at hippocampal CA1 synapses.

Postnatal development of hippocampal function has been reported in many mammalian species, including humans. To obtain synaptic evidence, we analyzed developmental changes in plasticity after an inhibitory avoidance task in rats. Learning performance was low in infants (postnatal 2 weeks) but clearly improved from the juvenile period (3-4 weeks) to adulthood (8 weeks). One hour after the training, we prepared brain slices and sequentially recorded miniature excitatory postsynaptic currents (mEPSCs) and inhibitory postsynaptic currents (mIPSCs) from the same hippocampal CA1 neuron. Although the training failed to affect the amplitude of either mEPSCs or mIPSCs at 2 weeks, it increased mEPSC, but not mIPSC, amplitude at 3 weeks. At 4 weeks, the training had increased the amplitude of both mEPSCs and mIPSCs, whereas mIPSC, but not mEPSC, amplitude was increased at 8 weeks. Because early-life physiological functions can affect performance, we also evaluated sensory-motor functions together with emotional state and found adequate sensory/motor functions from infancy to adulthood. Moreover, by analyzing performance of rats in multiple hippocampal-dependent tasks, we found that the developmental changes in the performance are task dependent. Taken together, these findings delineate a critical period for learning and plastic changes at hippocampal CA1 synapses.

The meaning of non-culprit stenosis in hyperacute stroke with large vessel occlusion.

BACKGROUND AND PURPOSE: To diagnose atherosclerotic occlusion mechanism in acute ischemic stroke patients with large vessel occlusion prior to revascularization therapy is challenging. The aim was to verify the relationship between atherosclerotic occlusion and non-culprit stenosis detected in urgent neuroimaging prior to interventional procedure. MATERIALS AND METHODS: This study collected hyperacute stroke with large vessel occlusion, who underwent revascularization therapy (intravenous thrombolysis, thrombectomy, or both). An atherosclerotic occlusion was defined as an occlusion that did not recanalize or had residual stenosis at the initially occluded lesion, ensured in the second angiographic imaging performed after 1 week. The remaining patients who did not fulfill the definition of atherosclerotic occlusion was classified as embolic occlusion. A non-culprit stenosis was defined as a ≥ 50%-99% stenosis located other than the culprit occluded artery. Logistic regression analyses were performed to determine the factors independently associated with atherosclerotic occlusion. RESULTS: A total of 162 patients (104 men, median age 76 years old) were enrolled in our study. Forty one patients (25%) was atherosclerotic occlusion. Non-culprit stenosis was frequently observed in the atherosclerotic occlusion group than the embolic occlusion group (68% vs. 26%, P < 0.001). The presence of non-culprit stenosis was independently associated with atherosclerotic occlusion (OR, 11.00; 95% CI, 3.96-30.52; P < 0.001). CONCLUSION: In hyperacute stroke receiving endovascular therapy, non-culprit stenosis identification may be needed in order to perform an adequate revascularization, especially for atherosclerotic occlusion.

Proximodistal Heterogeneity in Learning-promoted Pathway-specific Plasticity at Dorsal CA1 Synapses.

Contextual learning requires the delivery of AMPA receptors to CA1 synapses in the dorsal hippocampus. However, proximodistal heterogeneity of pathway-specific plasticity remains unclear. Here, we examined the proximodistal heterogeneity in learning-induced plasticity at the CA1 synapses with inputs from the entorhinal cortex layer III (ECIII) or from CA3. We subjected male rats to an inhibitory avoidance task and prepared acute hippocampal slices for whole-cell patch clamp experiments, where we stimulated ECIII-CA1 or CA3-CA1 input fibers to analyze evoked excitatory postsynaptic currents (EPSCs). Compared to untrained controls, trained rats exhibited higher AMPA/NMDA current ratios at CA3-CA1 synapses of proximal and intermediate, but not distal CA1 neurons, which suggested that region-specific plasticity occurred after learning. Moreover, trained rats exhibited higher AMPA/NMDA current ratios at ECIII-CA1 synapses of intermediate and distal, but not proximal CA1 neurons. These findings suggested the presence of proximodistal heterogeneity in pathway-specific postsynaptic plasticity. Regarding presynaptic plasticity, training slightly, but significantly increased the paired-pulse ratios of CA3-CA1 synapses of proximal and intermediate, but not distal CA1 neurons. Moreover, trained rats exhibited higher paired-pulse ratios at ECIII-CA1 synapses of intermediate and distal, but not proximal CA1 neurons, which suggested region-specific presynaptic plasticity. Finally, learning was clearly prevented by the bilateral microinjection of a plasticity blocker in the proximal or intermediate, but not distal CA1 subfields, which suggested functional heterogeneity along the proximodistal axis. Understanding region- and pathway-specific plasticity at dorsal CA1 synapses could aid in controlling encoded memory.

Temporal dynamics of learning-promoted synaptic diversity in CA1 pyramidal neurons.

Although contextual learning requires plasticity at both excitatory and inhibitory (E/I) synapses in cornu ammonis 1 (CA1) neurons, the temporal dynamics across the neuronal population are poorly understood. Using an inhibitory avoidance task, we analyzed the dynamic changes in learning-induced E/I synaptic plasticity. The training strengthened GABAA receptor-mediated synapses within 1 min, peaked at 10 min, and lasted for over 60 min. The intracellular loop (Ser408-409) of GABAA receptor ß3 subunit was also phosphorylated within 1 min of training. As the results of strengthening of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor-mediated synapses, CA1 pyramidal neurons exhibited broad diversity of E/I synaptic currents within 5 min. Moreover, presynaptic glutamate release probability at basal dendrites also increased within 5 min. To further quantify the diversified E/I synaptic currents, we calculated self-entropy (bit) for individual neurons. The neurons showed individual levels of the parameter, which rapidly increased within 1 min of training and maintained for over 60 min. These results suggest that learning-induced synaptic plasticity is critical immediately following encoding rather than during the retrieval phase of the learning. Understanding the temporal dynamics along with the quantification of synaptic diversity would be necessary to identify a failure point for learning-promoted plasticity in cognitive disorders.-Sakimoto, Y., Kida, H., Mitsushima, D. Temporal dynamics of learning-promoted synaptic diversity in CA1 pyramidal neurons.

Suppressive Effects of Cooling Compounds Icilin on Penicillin G-Induced Epileptiform Discharges in Anesthetized Rats.

More than 30% of patients with epilepsy are refractory and have inadequate seizure control. Focal cortical cooling (FCC) suppresses epileptiform discharges (EDs) in patients with refractory focal cortical epilepsy. However, little is known about the mechanism by which FCC inhibits seizures at 15°C, and FCC treatment is highly invasive. Therefore, new antiepileptic drugs are needed that produce the same effects as FCC but with different mechanisms of action. To address this need, we focused on transient receptor potential melastatin 8 (TRPM8), an ion channel that detects cold, which is activated at 15°C. We examined whether TRPM8 activation suppresses penicillin G (PG)-induced EDs in anesthetized rats. Icilin, a TRPM8 and TRP Ankyrin 1 agonist, was administered after PG injection, and a focal electrocorticogram (ECoG) and cortical temperature were recorded for 4 h. We measured spike amplitude, duration, firing rate, and power density in each band to evaluate the effects of icilin. PG-induced EDs and increased delta, theta, alpha, and beta power spectra were observed in the ECoG. Icilin suppressed EDs while maintaining cortical temperature. In particular, 3.0-mM icilin significantly suppressed PG-induced spike amplitude, duration, and firing rate and improved the increased power density of each band in the EDs to the level of basal activity in the ECoG. These suppressive effects of 3.0-mM icilin on EDs were antagonized by administering N-(3-aminopropyl)-2-[(3-methylphenyl) methoxy]-N-(2-thienylmethyl)-benzamide hydrochloride (AMTB), a selective TRPM8 inhibitor. Our results suggest that TRPM8 activation in epileptic brain regions may be a new therapeutic approach for patients with epilepsy.

Limitations of Local Brain Cooling on Generalized Motor Seizures from Unknown Foci in Awake Rats.

Local brain cooling of an epileptic focus at 15°C reduces the number of spikes on an electrocorticogram (ECoG), terminates seizures, and maintains neurological functions. In this study, we attempted to suppress generalized motor seizures (GMSs) by cooling a unilateral sensorimotor area. GMSs were induced in rats by intraperitoneal injection of bicuculline methiodide, an antagonist of gamma-aminobutyric acid. While monitoring the ECoG and behavior, the right sensorimotor cortex was cooled for 10 min using an implanted device. The number of spikes recorded from the cooled cortex significantly decreased to 71.2% and 62.5% compared with the control group at temperatures of 15 and 5°C (both P <0.01), respectively. The number of spikes recorded from the contralateral mirror cortex reduced to 61.7% and 62.7% (both P <0.05), respectively. The ECoG power also declined to 85% and 50% in the cooled cortex, and to 94% and 49% in the mirror cortex by the cooling at 15 and 5°C, respectively. The spikes regained in the middle of the cooling period at 15°C and in the late period at 5°C. Seizure-free durations during the 10-min periods of cooling at 15 and 5°C lasted for 4.1 ± 2.2 and 5.9 ± 1.1 min, respectively. Although temperature-dependent seizure alleviation was observed, the effect of local cortical cooling on GMSs was limited compared with the effect of local cooling of the epileptic focus on GSMs.

Reduction of spike generation frequency by cooling in brain slices from rats and from patients with epilepsy.

This study aimed to understand the mechanism by which brain cooling terminates epileptic discharge. Cortical slices were prepared from rat brains (n = 19) and samples from patients with intractable epilepsy that had undergone temporal lobectomy (n = 7). We performed whole cell current clamp recordings at approximately physiological brain temperature (35℃) and at cooler temperatures (25℃ and 15℃). The firing threshold in human neurons was lower at 25℃ (-32.6 mV) than at 35℃ (-27.0 mV). The resting potential and spike frequency were similar at 25℃ and 35℃. Cooling from 25℃ to 15℃ did not change the firing threshold, but the resting potential increased from -65.5 to -54.0 mV and the waveform broadened from 1.85 to 6.55 ms, due to delayed repolarization. These changes enhanced the initial spike appearance and reduced spike frequency; moreover, spike frequency was insensitive to increased levels of current injections. Similar results were obtained in rat brain studies. We concluded that the reduction in spike frequency at 15℃, due to delayed repolarization, might be a key mechanism by which brain cooling terminates epileptic discharge. On the other hand, spike frequency was not influenced by the reduced firing threshold or the elevated resting potential caused by cooling.

FABP3 in the Anterior Cingulate Cortex Modulates the Methylation Status of the Glutamic Acid Decarboxylase67 Promoter Region.

Polyunsaturated fatty acids (PUFAs) are essential for brain development and function. Increasing evidence has shown that an imbalance of PUFAs is associated with various human psychiatric disorders, including autism and schizophrenia. Fatty acid-binding proteins (FABPs), cellular chaperones of PUFAs, are involved in PUFA intracellular trafficking, signal transduction, and gene transcription. In this study, we show that FABP3 is strongly expressed in the GABAergic inhibitory interneurons of the male mouse anterior cingulate cortex (ACC), which is a component of the limbic cortex and is important for the coordination of cognitive and emotional behaviors. Interestingly, Fabp3 KO male mice show an increase in the expression of the gene encoding the GABA-synthesizing enzyme glutamic acid decarboxylase 67 (Gad67) in the ACC. In the ACC of Fabp3 KO mice, Gad67 promoter methylation and the binding of methyl-CpG binding protein 2 (MeCP2) and histone deacetylase 1 (HDAC1) to the Gad67 promoter are significantly decreased compared with those in WT mice. The abnormal cognitive and emotional behaviors of Fabp3 KO mice are restored by methionine administration. Notably, methionine administration normalizes Gad67 promoter methylation and its mRNA expression in the ACC of Fabp3 KO mice. These findings demonstrate that FABP3 is involved in the control of DNA methylation of the Gad67 promoter and activation of GABAergic neurons in the ACC, thus suggesting the importance of PUFA homeostasis in the ACC for cognitive and emotional behaviors.SIGNIFICANCE STATEMENT The ACC is important for emotional and cognitive processing. However, the mechanisms underlying its involvement in the control of behavioral responses are largely unknown. We show the following new observations: (1) FABP3, a PUFA cellular chaperone, is exclusively expressed in GABAergic interneurons in the ACC; (2) an increase in Gad67 expression is detected in the ACC of Fabp3 KO mice; (3) the Gad67 promoter is hypomethylated and the binding of transcriptional repressor complexes is decreased in the ACC of Fabp3 KO mice; and (4) elevated Gad67 expression and abnormal behaviors seen in Fabp3 KO mice are mostly recovered by methionine treatment. These suggest that FABP3 regulates GABA synthesis through transcriptional regulation of Gad67 in the ACC.

Mechanisms of motor learning mediated by synaptic plasticity in rat primary motor cortex.

Motor skill training induces long-term potentiation (LTP) and structural plasticity at dendritic spines in the primary motor cortex (M1). However, little is known about the plasticity of individual M1 neurons. Skilled motor coordination in rodents was recently assessed in studies using an accelerated rotor rod task with 1-2days of training. Using this model, we investigated the effects of motor training on both AMPA receptor-mediated excitatory synapses and GABAA receptor-mediated inhibitory synapses in layer II/III neurons in the M1. One day of the motor training strengthened AMPA receptor-mediated excitatory synapses and drastically reduced presynaptic GABA release probability. Two days of the training further strengthened AMPA receptor-mediated excitatory synapses as well as NMDA receptors, and increased presynaptic glutamate release while also restoring presynaptic GABA release probability. In this review, we discuss the dynamic changes observed in both glutamatergic and GABAergic plasticity as well as intrinsic plasticity after the training.

Slice Patch Clamp Technique for Analyzing Learning-Induced Plasticity.

The slice patch clamp technique is a powerful tool for investigating learning-induced neural plasticity in specific brain regions. To analyze motor-learning induced plasticity, we trained rats using an accelerated rotor rod task. Rats performed the task 10 times at 30-s intervals for 1 or 2 days. Performance was significantly improved on the training days compared to the first trial. We then prepared acute brain slices of the primary motor cortex (M1) in untrained and trained rats. Current-clamp analysis showed dynamic changes in resting membrane potential, spike threshold, afterhyperpolarization, and membrane resistance in layer II/III pyramidal neurons. Current injection induced many more spikes in 2-day trained rats than in untrained controls. To analyze contextual-learning induced plasticity, we trained rats using an inhibitory avoidance (IA) task. After experiencing foot-shock in the dark side of a box, the rats learned to avoid it, staying in the lighted side. We prepared acute hippocampal slices from untrained, IA-trained, unpaired, and walk-through rats. Voltage-clamp analysis was used to sequentially record miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) from the same CA1 neuron. We found different mean mEPSC and mIPSC amplitudes in each CA1 neuron, suggesting that each neuron had different postsynaptic strengths at its excitatory and inhibitory synapses. Moreover, compared with untrained controls, IA-trained rats had higher mEPSC and mIPSC amplitudes, with broad diversity. These results suggested that contextual learning creates postsynaptic diversity in both excitatory and inhibitory synapses at each CA1 neuron. AMPA or GABAA receptors seemed to mediate the postsynaptic currents, since bath treatment with CNQX or bicuculline blocked the mEPSC or mIPSC events, respectively. This technique can be used to study different types of learning in other regions, such as the sensory cortex and amygdala.