Germinomas of the basal ganglia and thalamus: Four case reports

BACKGROUND The early diagnosis of basal ganglia and thalamus germinomas is often difficult due to the absence of elevated tumor markers,and atypical clinical symptoms and neuroimaging features.CASE SUMMARY Four male children aged 8 to 15 years were diagnosed with germinomas in the basal ganglia and thalamus by stereotactic biopsy from 2017 to 2019.All patients developed hemiplegia except patient 4 who also had cognitive decline,speech disturbance,nocturnal enuresis,polydipsia,polyuria,precocious puberty and abnormalities of thermoregulation.All four cases were alpha-fetoprotein and beta-human chorionic gonadotrophin(p-HCG)negative except patient 3 who had slightly elevated p-HCG in cerebrospinal fluid(CSF).No malignant cells were detected in the patients'CSF.Brain magnetic resonance imaging findings were diverse in these patients with the exception of the unique and common characteristics of ipsilateral hemisphere atrophy,especially in the cerebral peduncle.All patients were diagnosed with germinomas of the basal ganglia and thalamus by stereotactic brain biopsy.CONCLUSION Stereotactic brain biopsy is necessary to confirm the diagnosis of ectopic germinomas.Serial neuroimaging studies can not only differentiate disease but also determine the biopsy site.

Increased thalamocortical connectivity from the affected thalamus to the unaffected hemisphere in a stroke patient

Consciousness is controlled by complicated actions of various neural structures(Schiff,2010;Long et al.,2016).The thalamocortical connections between the central thalamus and cerebral cortex are considered an important neural structure for consciousness(Laureys et al.,2000;Schiff,2010;Jang and Lee,2015).Here,we report a patient who revealed increased thalamocortical connectivity from the affected thalamus to the unaffected hemisphere through interthalamic adhesion.

Collective behavior of cortico-thalamic circuits:Logic gates as the thalamus and a dynamical neuronal network as the cortex

This paper introduces a two-layer network to investigate the effects of cortico-thalamic circuits on the cortex’s collective behavior.In the brain,different parts of the cortex collaborate to process information.One of the main parts,which is the path of different cortex contacts,is the thalamus whose circuit is referred to as the"vertical"cortico-thalamic connectivity.Thalamus subnuclei can participate in the processing of the information that passes through them.It has been shown that they play the functional role of logic gates(AND,OR and XOR).To study how these thalamus circuits affect the cortical neuron behavior,a two-layer network is proposed wherein the cortex layer is composed of Hindmarsh–Rose models and the thalamus layer is constructed with logic gates.Results show that considering these logic gates can lead the network towards different synchronization,asynchronization,chimera and solitary patterns.It is revealed that for AND-gate and OR-gate,increasing the number of gates or their outputs can increase and decrease the network’s coherency in excitatory and inhibitory cases,respectively.However,considering XOR-gates always results in the chimera state.

ACETYLCHOLINESTERASE HISTOCHEMISTRY OF THE THALAMUS IN THE PRIMATE

Objective To observe the distribution of acetylcholinesterase activity in the thalamus of the monkey.Methods Histochemical method was used to detect the acetylcholinesterase activity in the thalamus.Results Acetylcholinesterase was found to be inhomogeneous distribution in the primate thalamus and to reveal previously uncovered inhomogeneity within certain thalamic nuclei and their subdivisions. The medial, ventral and posterior nuclear groups displayed markedly uneven acetylcholinesterase reaction.In the mediodorsal nucleus,three distinct sbudivisions were revealed by acetylcholinesterase histochemistry, medial magnocellular part, ventral sector of central parvicellular part and dorsolateral sector of lateral pars multiformity showed weak, moderate and strong acetylcholinesterase activity, respectively. In the ventral nuclear group, acetylcholinesterase histochemistry was strong in the medial part of ventral posterior nucleus, moderate in the magnocellular part of ventral anterior, caudal, medial, oral and pars postrema parts of ventral lateral nucleus, as well as lateral part of ventral posterior nucleus, poor and weak in the inferior part of ventral posterior nucleus, par compacta of the medial part of ventral posterior nucleus and parvicellular part of ventral anterior nucleus. In the pulvinar nucleus, acetylcholinesterase reaction ranged from weak, moderate to strong in the parts of the oral, medial and lateral, as well as inferior of this nucleus, respectively. Regional variations of acetylcholinesterase activity within the thalamic nuclei and their subdivisions can help to identify them by acetylcholinesterase histochemistry. In addition, the dark patches of strong acetylcholinesterase activity contrasting with a lighter surrounding matrix were revealed within the parvicellular part and pars multiformis of mediodorsal nucleus, paracentral nucleus, central lateral nucleus, pars postrema part of ventral lateral nucleus and medial habenula nucleus, as well as medial part of pulvinar necleus, respectively.Conclusion Acetylcholinesterase histochemistry can serve as useful marker for delineating the thalamic nuclei and their sbudivisions. The different distribution of acetylcholinesterase histochemistry implies the activity of thalamic nuclei may be modulated by cholinergic systems.

Some Characteristics of Neurons in the Reticular Nucleus of the Thalamus (Preliminary Data)

Our general understanding of the function of neurons is that dendrites receive information that is relayed to the axon, where action potentials are initiated and propagated to eventually trigger neurotransmitter release at synaptic terminals. Although for a number of neuron types in the mammalian brain, many neuron types do not follow this classical polarity pattern. In fact, dendrites may be the site of action potentials initiation and propagation. It should be noted that convincing evidence has been obtained for the existence of dendritic action potentials in hippocampal and neocortical neurons. With regard to the dendrite potentials of thalamic neurons in general and specifically the reticular nucleus of the thalamus, it has not yet been reported. The results of this study demonstrate, for the first time, that generation of spike potentials of different amplitudes was observed in the activity of the thalamic reticular nucleus neurons. The generation of one action potential does not interfere with the generation of another, and a spike potential of smaller amplitude can occur at the ascending or descending phase of the spike potential of large amplitude. It can be argued that the spike potentials of lower amplitudes arising in the thalamic reticular nucleus neuron are of dendrite origin. Given both the strategic position and the functional purpose of the TRN, it can be assumed that the neurons of this structure must each time be discharged with spike potentials in order to carry out their modulating effect on other areas of the nervous system of the brain without leakage.

Elevated Neurosteroids in the Lateral Thalamus Relieve Neuropathic Pain in Rats with Spared Nerve Injury

Neurosteroids are synthesized in the nervous system from cholesterol or steroidal precursors imported from peripheral sources. These compounds are important allosteric modulators of γ-aminobutyric acid A receptors （GABAARs）, which play a vital role in pain modulation in the lateral thalamus, a main gate where somatosensory information enters the cerebral cortex. Using high-perfor mance liquid chromatography/tandem mass spectrometry, we found increased levels of neurosteroids （pregnenolone, progesterone, deoxycorticosterone, allopregnanolone, and tetrahydrodeoxycorticosterone） in the chronic stage of neuropathic pain （28 days after spared nerve injury） in rats.The expression of the translocator protein TSPO, the upstream steroidogenesis rate-limiting enzyme, increased at the same time. In vivo stereotaxic microinjection of neurosteroids or the TSPO activator AC-5216 into the lateral thalamus （AP -3.0 mm, ML 4-3.0 mm, DV 6.0 mm） alleviated the mechanical allodynia in neuropathic pain, while the TSPO inhibitor PK 11195 exacerbated it. The analgesic effects of AC-5216 and neurosteroids were sig- nificantly attenuated by the GABAAR antagonist bicuculline. These results suggested that elevated neurosteroids in the lateral thalamus play a protective role in the chronic stage of neuropathic pain.

High-frequency stimulation of anterior nucleus thalamus improves impaired cognitive function induced by intra-hippocampal injection of Aβ1-40 in rats

Background The advent of brain stimulation techniques to treat movement disorders and psychiatric diseases has shown potential to decode the neural mechanism that underlies the cognitive process by modulating the interrupted circuit.Here,the present investigation aimed at evaluating the influence of deep brain stimulation of the anterior nucleus thalamus （ANT-DBS） on memory.Methods Thirty-two rats were randomized into phosphate buffer saline （PBS） group （n=8,rats received PBS injections without implantation of electrodes into the ANT）,Alzheimer＇s dementia （AD） group （n=8,rats received Aβ1-40 injections without implantation of electrodes into the ANT）,ANT sham stimulation group （n=8,rats received Aβ1-40 injections with implantation of electrodes into the ANT but without stimulation） and ANT stimulation group （n=8,rats received Aβ1-40 injections with implantation of electrodes into the ANT and stimulation）.A Morris maze test was used for determining the effect of electrical stimulation on cognitive function in rats.The data were assessed statistically with one-way analysis of variance （ANOVA） followed by Tukey＇s tests for multiple post hoc comparisons.Results The data showed that in the training test,PBS group and AD group managed to learn the hidden-platform faster and faster while AD group needed a significantly longer time to reach the platform than PBS group （P ＜0.05）.Meanwhile,ANT stimulation group demonstrated a significantly shorter time to reach the platform （P ＜0.05） compared to the AD group,while there was no significant difference between the ANT sham stimulation group and the AD group （P ＞0.05）.On the probe test,the AD group spent less time （（10.15±2.34） seconds） in the target quadrant than the PBS group （（28.20±2.75） seconds） （P ＜0.05）.And the times of platform-traversing of the AD group （3.35±1.12） significantly decreased compared with the PBS group （8.69±2.87） （P ＜0.05）.However,the times of platform-traversing and the time spent in the target quadrant of the ANT stimulation group significantly increased compared to the AD group （P ＜0.05）,while times of platformtraversing or the time spent in the target quadrant was not significantly different between the ANT sham stimulation group and the AD group （P ＞0.05）.Conclusion Bilateral high-frequency stimulation of the ANT may be useful as a potential therapeutic modality for cognitive dysfunction in AD.

Altered Resting-State Signals in Patients with Acute Stroke In or Under the Thalamus

Abstract Previous studies have suggested that cortical functional reorganization is associated with motor recovery after stroke and that normal afferent sensory information is very important in that process. In this study, we selected patients who had a stroke in or under the thalamus, with potentially impaired afferent sensory information and analyzed the differences between these patients and healthy controls at three levels： brain regions, the functional con- nectivity between brain areas, and the whole-brain func- tional network. Compared with healthy controls, regionalhomogeneities in the left middle temporal gyrus decreased and functional connectivity between the left middle tem- poral gyrus and the stroke area increased in the patients. However, there was no significant change in the whole- brain functional network. By focusing on stroke located in or under the thalamus, our study contributes to wider inquiries into understanding and treating stroke.

Effect of anterior nucleus of thalamus stimulation on glucose metabolism in hippocampus of epileptic rats

Background Electrical stimulation of seizures. In this study, we investigated epileptic rats. the anterior nucleus of the thalamus （ANT） appears to be effective against changes in glucose metabolism during high-frequency stimulation of ANT in Methods Three groups of rats were used： （1） a stimulation group （n=12）, （2） a sham stimulation group （n=12） with seizures induced by stereotactic administration of kainic acid （KA）, and （3） a control group （n=12） with sham surgery. Concentric bipolar electrodes were stereotaxically implanted unilaterally in the ANT. High-frequency stimulation was performed in each group except the sham stimulation group. Microdialysis probes were lowered into the CA3 region of the hippocampus unilaterally but bilaterally in the.stimulation group. The concentrations of glucose, lactate, and pyruvate in dialysate samples were determined by an ISCUS microdialysis analyzer. Results The extracellular concentrations of lactate and lactate/pyruvate ratio （LPR） of epileptic rats were significantly higher than in control rats （P=0.020, P=0.001; respectively）. However, no significant difference in the concentration of glucose and pyruvate was found between these groups （P 〉0.05）. Electrical stimulation of ANT induced decreases in lactate and LPR in the ipsilateral hippocampus （KA injected） of the stimulation group （P 〈0.05）, but it did not influence the glucose metabolism in the contralateral hippocampus （P 〉0.05）. Conclusions This study demonstrated that the glycolysis was inhibited in the ipsilateral hippocampus of epileptic rats during electrical ANT stimulation. These findings may provide useful information for better understanding the mechanism of ANT-deep brain stimulation.

Properties of oscillatory neuronal activity in the basal ganglia and thalamus in patients with Parkinson’s disease

Background:The cardinal features of Parkinson’s disease(PD)are bradykinesia,rigidity and rest tremor.Abnormal activity in the basal ganglia is predicted to underlie the mechanism of motor symptoms.This study aims to characterize properties of oscillatory activity in the basal ganglia and motor thalamus in patients with PD.Methods:Twenty-nine patients with PD who underwent bilateral or unilateral electrode implantation for subthalamic nucleus(STN)DBS(n=11),unilateral pallidotomy(n=9)and unilateral thalamotomy(n=9)were studied.Microelectrode recordings in the STN,globus pallidus internus(GPi)and ventral oral posterior/ventral intermediate of thalamus(Vop/Vim)were performed.Electromyography of the contralateral limbs was recorded.Single unit characteristics including interspike intervals were analyzed.Spectral and coherence analyses were assessed.Mean spontaneous firing rate(MSFR)of neurons was calculated.Analysis of variance and χ^(2) test were performed.Results:Of 76 STN neurons,39.5% were 4–6 Hz band oscillatory neurons and 28.9% were β frequency band(βFB)oscillatory neurons.The MSFR was 44.2±7.6 Hz.Of 62 GPi neurons,37.1% were 4–6 Hz band oscillatory neurons and 27.4% were βFB neurons.The MSFR was 80.9±9.6 Hz.Of 44 Vop neurons,65.9% were 4–6 Hz band oscillatory neurons and 9%were βFB neurons.The MSFR was 24.4±4.2 Hz.Of 30 Vim oscillatory neurons,70% were 4–6 Hz band oscillatory neurons and 13.3% were β FB neurons.The MSFR was 30.3±3.6 Hz.Further analysis indicated that proportion of βFB oscillatory neurons in STN and GPi was higher than that of similar neurons in the Vop and Vim(P<0.05).Conversely,the proportion of 4–6 Hz band oscillatory neurons and tremor related neurons in the Vim and Vop was higher than that of STN and GPi(P<0.05).The highest MSFR was for GPi oscillatory neurons whereas the lowest MSFR was for Vop oscillatory neurons(P<0.005).Conclusion:The alterations in neuronal activity in basal ganglia play a critical role in generation of parkinsonism.β oscillatory activity is more prominent in basal ganglia than in thalamus suggesting that the activity likely results from dopaminergic depletion.While both basal ganglia and thalamus have tremor activity,the thalamus appears to play a more important role in tremor production,and basal ganglia β oscillatory activity might be the trigger.

Projections from Infralimbic Cortex to Paraventricular Thalamus Mediate Fear Extinction Retrieval

The paraventricular nucleus of the thalamus(PVT),which serves as a hub,receives dense projections from the medial prefrontal cortex(mPFC)and projects to the lateral division of central amygdala(CeL).The infralimbic(IL)cortex plays a crucial role in encoding and recalling fear extinction memory.Here,we found that neurons in the PVT and IL were strongly activated during fear extinction retrieval.Silencing PVT neurons inhibited extinction retrieval at recent time point(24 h after extinction),while activating them promoted extinction retrieval at remote time point(7 d after extinction),suggesting a critical role of the PVT in extinction retrieval.In the mPFC-PVT circuit,projections from IL rather than prelimbic cortex to the PVT were dominant,and disrupting the IL-PVT projection suppressed extinction retrieval.Moreover,the axons of PVT neurons preferentially projected to the CeL.Silencing the PVT-CeL circuit also suppressed extinction retrieval.Together,our findings reveal a new neural circuit for fear extinction retrieval outside the classical IL-amygdala circuit.

Distinct Roles of Dopamine Receptors in the Lateral Thalamus in a Rat Model of Decisional Impulsivity

The thalamus and central dopamine signaling have been shown to play important roles in high-level cognitive processes including impulsivity. However, little is known about the role of dopamine receptors in the thalamus in decisional impulsivity. In the present study,rats were tested using a delay discounting task and divided into three groups： high impulsivity（HI）, medium impulsivity（MI）, and low impulsivity（LI）. Subsequent in vivo voxel-based magnetic resonance imaging revealed that the HI rats displayed a markedly reduced density of gray matter in the lateral thalamus compared with the LI rats. In the MI rats, the dopamine D1 receptor antagonist SCH23390 or the D2 receptor antagonist eticlopride was microinjected into the lateral thalamus. SCH23390 significantly decreased their choice of a large, delayed reward and increased their omission of lever presses. In contrast,eticlopride increased the choice of a large, delayed reward but had no effect on the omissions. Together, our results indicate that the lateral thalamus is involved in decisional impulsivity, and dopamine D1 and D2 receptors in the lateral thalamus have distinct effects on decisional impulsive behaviors in rats. These results provide a new insightinto the dopamine signaling in the lateral thalamus in decisional impulsivity.

Altered asymmetries of resting-state MRI in the left thalamus of first-episode schizophrenia

Background:Schizophrenia(SCZ)is a complex psychiatric disorder associated with widespread alterations in the subcortical brain structure.Hemispheric asymmetries are a fundamental organizational principle of the human brain and relate to human psychological and behavioral characteristics.We aimed to explore the state of thalamic lateralization of SCZ.Methods:We used voxel-based morphometry(VBM)analysis,whole-brain analysis of low-frequency fluctuations(ALFF),fractional amplitude of low-frequency fluctuations(fALFF),and resting-state seed-based functional connectivity(FC)analysis to investigate brain structural and functional deficits in SCZ.Also,we applied Pearson’’s correlation analysis to validate the correlation between Positive and Negative Symptom Scale(PANSS)scores and them.Results:Compared with healthy controls,SCZ showed increased gray matter volume(GMV)of the left thalamus(t=2.214,p=0.029),which positively correlated with general psychosis(r=0.423,p=0.010).SCZ also showed increased ALFF in the putamen,the caudate nucleus,the thalamus,fALFF in the nucleus accumbens(NAc),and the caudate nucleus,and decreased fALFF in the precuneus.The left thalamus showed significantly weaker resting-state FC with the amygdala and insula in SCZ.PANSS negative symptom scores were negatively correlated with the resting-state FC between the thalamus and the insula(r=-0.414,p=0.025).Conclusions:Collectively,these results suggest the possibility of aberrant laterality in the left thalamus and its FC with other related brain regions involved in the limbic system.

Paraventricular Thalamus as A Major Thalamic Structure for Wake Control

The thalamus is the gate of the cerebral cortex, the ultimate target for the neural networks controlling behavioral states and cognitive functions. According to the reticular theory initially proposed by Moruzzi and Magoun, excitatory inputs from large reticular zones of the brainstem via widespread intra- and extra-thalamocortical systems finally activate the cerebral cortex to cause generalized cortical activation and wakefulness [1]. This theory proposes a central relay role to the thalamus for cortical activation as supported by early studies using neurodegeneration techniques and by the elegant work of Steriade’s group and other investigators illustrating the electrophysiological mechanisms of the thalamocortical system at the cellular level during wakefulness, rapid eye-movement sleep (REMs) and non-REM sleep (NREMs)[2].

Neuronal firing in the globus pallidus internus and the ventrolateral thalamus related to parkinsonian motor symptoms

Background It has been proposed that parkinsonian motor signs result from hyperactivity in the output nucleus of the basal ganglia, which suppress the motor thalamus and cortical areas. This study aimed to explore the neuronal activity in the globus pallidus internus （GPi） and the ventrolateral thalamic nuclear group （ventral oral posterior/ventral intermediate, Vop/Vim） in patients with Parkinson＇s disease （PD）. Methods Twenty patients with PD who underwent neurosurgery were studied. Microelectrode recording was performed in the GPi （n=10） and the Vop/Vim （n=10） intraoperatively. Electromyography （EMG） contralateral to the surgery was simultaneously performed. Single unit analysis was carried out. The interspike intervals （ISI） and coefficient of variation （CV） of ISI were calculated. Histograms of ISI were constructed. A unified Parkinson＇s disease rating scale （UPDRS） was used to assess the clinical outcome of surgery. Results Three hundred and sixty-three neurons were obtained from 20 trajectories. Of 175 GPi neurons, there were 15.4% with tremor frequency, 69.2% with tonic firing, and 15.4% with irregular discharge. Of 188 thalamic neurons, there were 46.8% with tremor frequency, 22.9% with tonic firing, and 30.3% with irregular discharge. The numbers of three patterns of neuron in GPi and Vop/Vim were significantly different （P 〈0.001）. ISI analysis revealed that mean firing rate of the three patterns of GPi neurons was （80.9±63.9） Hz （n=78）, which was higher than similar neurons with 62.9 Hz in a normal primate. For the Vop/Vim group, ISI revealed that mean firing rate of the three patterns of neurons （n=95） was （23.2±17.1） Hz which was lower than similar neurons with 30 Hz in the motor thalamus of normal primates. UPDRS indicated that the clinical outcome of pallidotomy was （64.3±29.5）%, （83.4±19.1）% and （63.4±36.3）%, and clinical outcome of thalamotomy was （92.2±12.9）%, （68.0±25.2）% and （44.3±7.2）% for tremor, rigidity and bradykinesia, respectively. A significant difference of tremor and rigidity was found between GPi and VopNim （P 〈0.05）. Conclusions Different changes in neuronal firing rate and the pattern in GPi and Vop/Vim are likely responsible for parkinsonian motor signs. The results support the view that abnormal neuronal activity in GPi and Vop/Vim are involved in the pathophysiology of parkinsonism.

Ventromedial Thalamus-Projecting DCN Neurons Modulate Associative Sensorimotor Responses in Mice

The deep cerebellar nuclei(DCN)integrate various inputs to the cerebellum and form the final cerebellar outputs critical for associative sensorimotor learning.However,the functional relevance of distinct neuronal subpopulations within the DCN remains poorly understood.Here,we examined a subpopulation of mouse DCN neurons whose axons specifically project to the ventromedial(Vm)thalamus(DCNVm neurons),and found that these neurons represent a specific subset of DCN units whose activity varies with trace eyeblink conditioning(tEBC),a classical associative sensorimotor learning task.Upon conditioning,the activity of DCNVm neurons signaled the performance of conditioned eyeblink responses(CRs).Optogenetic activation and inhibition of the DCNVm neurons in well-trained mice amplified and diminished the CRs,respectively.Chemogenetic manipulation of the DCNVm neurons had no effects on non-associative motor coordination.Furthermore,optogenetic activation of the DCNVm neurons caused rapid elevated firing activity in the cingulate cortex,a brain area critical for bridging the time gap between sensory stimuli and motor execution during tEBC.Together,our data highlights DCNVm neurons’function and delineates their kinematic parameters that modulate the strength of associative sensorimotor responses.

INFLUENCE OF 5-HYDROXYTRYPTAMINE MICRO INJECTED INTO PREOPTIC AREA ON ELECTRO ACTIVITIES OF PAIN RESPONSE NEURONS IN PARAFASCICULAR NUCLEUS OF THALAMUS IN RAT

Many research works through out the world show that the preoptic area(POA) is a region concerned with analgesia. Electric stimulation to this region could enhance markedly pain threshold and exert an analgesic effect. Central 5-hydroxytryptamine (5-HT) plays an important role in pain mediation. Acupuncture could accelerate the synthe-

Photochemically induced thalamus infarction impairs cognition in a mouse model

Background Small subcortical infarcts account for up to 25%of ischaemic strokes.Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain.Studies have shown that thalamus infarction is associated with cognitive decline.However,due to the lack of proper animal models,little is known about the mechanism.We aimed to establish a focal thalamus infarction model,characterise the infarct lesion and assess functional effects.Methods Male C57BL/6J mice were anaesthetised,and Rose Bengal dye was injected through the tail vein.The right thalamus was illuminated with green laser light by stereotactic implantation of optic fibre.Characteristics of the infarct and lesion evolution were evaluated by histological analysis and 7T MRI at various times.The cognitive and neurological functions were assessed by behavioural tests.Retrograde tracing was performed to analyse neural connections.Results An ischaemic lesion with small vessel occlusion was observed in the thalamus.It became a small circumscribed infarct with reactive astrocytes accumulated in the infarct periphery on day 21.The mice with thalamic infarction demonstrated impaired learning and memory without significant neurological deficits.Retrogradely labelled neurons in the retrosplenial granular cortex were reduced.Conclusion This study established a mouse model of thalamic lacunar infarction that exhibits cognitive impairment.Neural connection dysfunctions may play a potential role in post-stroke cognitive impairment.This model helps to clarify the pathophysiology of post-stroke cognitive impairment and to develop potential therapies.

Map activation of various brain regions using different frequencies of electroacupuncture ST36,utilizing the FosCreER strategy

Objective:Electroacupuncture(EA)is an alternative treatment option for pain.Different frequencies of EA have different painrelieving effects;however,the central mechanism is still not well understood.Methods:The Fos2A-iCreER(TRAP):Ai9 mice were divided into three groups(sham,2 Hz,and 100 Hz).The mice were intraperitoneally injected with 4-hydroxytamoxifen(4-OHT)immediately after EA at Zusanli(ST36)for 30 min to record the activated neurons.One week later,the mice were sacrificed,and the number of TRAP-treated neurons activated by EA in the thalamus,amygdala,cortex,and hypothalamus was determined.Results:In the cortex,2 Hz EA activated more TRAP-treated neurons than 100 Hz EA did in the cingulate cortex area 1(Cg1)and primary somatosensory cortex(S1),and 2 and 100 Hz EAs did not differ from sham EA.TRAP-treated neurons activated by 2 Hz EA were upregulated in the insular cortex(IC)and secondary somatosensory cortex(S2)compared with those activated by 100 Hz and sham EA.In the thalamus,the number of TRAP-treated neurons activated by 2 Hz EA was elevated in the paraventricular thalamic nucleus(PV)compared with those activated by sham EA.In the ventrolateral thalamic nucleus(VL),the number of TRAPtreated neurons activated by 2 Hz EA was significantly upregulated compared with those activated by 100 Hz EA,and sham EA showed no difference compared with 2 or 100 Hz EA.TRAP-treated neurons were more frequently activated in the ventral posterolateral thalamic nucleus(VPL)by 2 Hz EA than by 100 Hz or sham EA.Conclusions:Low-frequency EA ST36 effectively activates neurons in the Cg1,S1,S2,IC,VPL,PV,and VL.The enhanced excitability of the aforementioned nuclei induced by low-frequency EA may be related to its superior efficacy in the treatment of neuropathological pain.

Properties of tactile responses of neurons in rat thalamic ventroposterolateral nucleus

Objective To determine whether the convergences of tactile information also occur at thalamic ventroposterolateral nucleus in rats, we investigated the properties of tactile responses of the thalamic ventroposterolateral nucleus in rats. Methods Unit responses were recorded extracellularly from thalamic ventroposterolateral nucleus in anesthetized rats. Results Among 156 neurons examined, 140 neurons （89.7%） had the single, continual and small receptive fields, and 16 neurons （10.3%） had two discrete receptive fields. Some neurons exhibited different responses to the same intensity stimulation which delivered to different points in their receptive fields. In addition, 4.5% neurons （n -- 7） responded only to locomotive stimulation but not to a punctiform tactile stimulation. Conclusion The majority of neurons in ventroposterolateral nucleus of rats have the spatial, temporal and submodal characteristics of cutaneous receptors, while the minority of neurons exhibit the responses of interaction of different peripheral receptors. Therefore, it is con- cluded that there are convergences of tactile information at the ventroposterolateral nucleus of rats.