Direct Corticosteroid Modulation of GABAergic Neurons in the Anterior Hypothalamic Area of GAD65-eGFP Mice

Corticosterone is known to modulate GABAergic synaptic transmission in the hypothalamic paraventricular nucleus. However, the underlying receptor mechanisms are largely unknown. In the anterior hypothalamic area (AHA), the sympathoinhibitory center that project GABAergic neurons onto the PVN, we examined the expression of glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) of GABAergic neurons using intact GAD65-eGFP transgenic mice, and the effects of corticosterone on the burst firing using adrenalectomized transgenic mice. GR or MR immunoreactivity was detected from the subpopulations of GABAergic neurons in the AHA. The AHA GABAergic neurons expressed mRNA of GR (42%), MR (38%) or both (8%). In addition, in brain slices incubated with corticosterone together with RU486 (MR-dominant group), the proportion of neurons showing a burst firing pattern was significantly higher than those in the slices incubated with vehicle, corticosterone, or corticosterone with spironolactone (GR-dominant group; 64 vs. 11~14%, p< 0.01 by χ²-test). Taken together, the results show that the corticosteroid receptors are expressed on the GABAergic neurons in the AHA, and can mediate the corticosteroid-induced plasticity in the firing pattern of these neurons. This study newly provides the experimental evidence for the direct glucocorticoid modulation of GABAergic neurons in the AHA in the vicinity of the PVN.     

Microcircuitry of posterior cingulate cortex in vitro: electrophysiology and laminar analysis using the current source density method

We used current source density (CSD) analysis of a laminar profile of subicular stimulus-evoked field potentials recorded in cortical slices in vitro to characterize the interlaminar microcircuitry of posterior cingulate cortex. Neuroanatomic and electrophysiologic data indicate that subiculocingulate tract (SCT) afferents monosynaptically excite apical dendrites of deep laminae (V–VI) neurons, evoking pure EPSPs, while superficial laminae (II/III–IV) neurons are driven polysynaptically, evoking a mixture of longer latency EPSPs and IPSPs. Consistent with this model, CSD analysis of field potential laminar profiles supports the conclusion that activation of excitatory subicular afferent terminal fields in superfical laminae of cingulate cortex elicits primary monosynaptic activation of apical dendrites of deep lamina (V–VI) pyramids. Subsequent EPSP propagation to the somata of these pyramids generated synchronous action potential discharges which appeared to elicit delayed polysynaptic activation of superficial laminae pyramids and interneurons. Latency differences between SCT-stimulus-evoked EPSPs and action potentials in superficial and deep laminae were minimized by stimulus train frequencies of 5–8 Hz, indicating that the proposed microcircuitry can show functional tuning at frequencies characteristic of hippocampal neuronal activity (theta). Such tuning suggests that hippocampal output activity frequency and phase locked to theta rhythm will be preferentially gated through cingulate cortex.     

Excitatory effect of adenosine on neurotransmission in the slices of superior colliculus and hippocampus of guinea pig

Postsynaptic potential (PSP) was recorded from the CA3 region of the pyramidal cell layer of hippocampal slices and from the superficial gray layer of superior collicular slices from guinea pigs. In the hippocampal slices, application of adenosine to the perfusion medium at a concentration of 10 nM to 1 μM enhanced the amplitude of the PSP and at concentrations greater than 10 μM it depressed the PSP. The dose-response curve of the effect of adenosine on neurotransmission in the hippocampus thus showed an excitatory and inhibitory biphasic pattern according to the concentrations applied. However, in superior collicular slices, application of adenosine at concentrations of more than 10 nM enhanced the amplitude of the PSP and there was no inhibition by adenosine even at a concentration of 1 mM.     

Electrical membrane properties of rat subthalamic neurons in an in vitro slice preparation

The electrical membrane properties of subthalamic (STH) neurons and their response characteristics to stimulation of the internal capsule (IC) were studied in an in vitro slice preparation. Most STH neurons recorded exhibited spontaneous repetitive firing. The input resistance of STH neurons was 146 +/- 48 M omega and showed both an anomalous and a delayed rectification when the membrane was hyperpolarized or depolarized by current injections. In neurons with the membrane potential less negative than 65 mV, depolarizing current pulses generated repetitive firing with the maximum frequency of up to 500 Hz. Two types of tetrodotoxin (TTX)-resistant cobalt-sensitive potentials, slow depolarizing potential and slow action potential, were observed in STH neurons. The slow depolarizing potential had a long duration (over 500 ms in some cases) and was able to trigger repetitive firing. The slow action potential had a duration of about 30 ms and triggered a burst of firing. The slow action potential was seen only when the neurons were hyperpolarized to more negative than 65 mV by a current injection. Electrical stimulation of IC evoked monosynaptic inhibitory postsynaptic potentials (IPSPs) in most of the neurons examined. The polarity of IPSPs was reversed in the depolarizing direction by intracellular injection of Cl-. Bath application of bicuculline markedly suppressed IPSPs and unmasked monosynaptic excitatory postsynaptic potentials (EPSPs). The EPSP was able to trigger a slow depolarization with repetitive firing or a slow action potential with burst of firing when the neuron was hyperpolarized by a continuous current injection. The results demonstrated that STH neurons in an in vitro preparation have spontaneous discharges, high input resistance, capability to generate high-frequency firing, and Ca potentials. The pattern of responses of STH neurons to synaptic inputs is dependent on their membrane potentials.     

人参片对大鼠血脂水平及延缓衰老作用的实验研究

目的　了解人参片对果蝇寿命及 12月龄 SD大鼠血脂水平及体内脂质过氧化的影响。　方法　采用果蝇生存试验和抗氧化作用试验的方法进行。　结果　延长果蝇半数死亡时间、平均寿命、平均最高寿命 ;2周后对 12月龄大鼠体重的增长有明显的抑制作用 ;4周后对动物体内脂质过氧化无显著性影响 ;8周后对机体血脂水平及体内脂质过氧化状态有显著的抑制作用 ,表现在能降低血清中总胆固醇、甘油三脂水平 ,升高血液、肝脏中超氧化物歧化酶的活力 ,抑制血清、肝脏中 MDA的生成。　结论　人参片具有减缓大鼠体重的增长、降脂及延缓衰老的作用。     

64层螺旋CT扫描对早期诊断肝癌、局灶性结节增生的特异性及敏感性分析

目的 探讨64层螺旋CT在早期诊断原发性肝癌（HCC）与局灶性结节增生（FNH）中的应用及敏感性、特异性分析。方法 选取2016年1月至2017年1月与我院就诊高度怀疑HCC的56例患者及高度怀疑FNH的45例患者作为可研究对象。所有患者均接受64层螺旋CT平扫及增强扫描,并与术后病理证实结果比较,分析螺旋CT对HCC、FNH早期诊断的敏感性与特异性,并对比二者在CT增强扫描时不同能量水平下的对比噪声比（CNR）情况以及能谱定量参数值情况。结果 64层螺旋CT对HCC早期诊断的敏感性为96.23%,特异性为66.67%,准确性为92.86%;对FNH早期诊断的敏感性为92.68%,特异性为75.00%,准确性为86.67%。增强扫描动脉期时HCC、FNH患者CNR均呈明显的下降状态,并且能量越高则CNR越低,HCC与FNH患者的CNR值比较存在显著差异（P<0.05）;门脉期FNH患者CNR逐渐降低,而在40 keV时获取最佳CNR,HCC患者则表现为CNR先升后降,80 keV时获取最佳CNR,HCC、FNH患者在80~120keV间的CNR值比较存在显著差异（P<0.05）,但在40 keV时比较无显著差异（P>0.05）。结论 64层螺旋CT在早期诊断及鉴别诊断HCC、FNH中具有重要的临床价值,检出效能、敏感性、特异性较高,具有临床应用及推广价值。     

T1 mapping cardiovascular magnetic resonance imaging to detect myocarditis—Impact of slice orientation on the diagnostic performance

BackgroundT1 mapping is a promising diagnostic tool to improve the diagnostic accuracy of cardiovascular magnetic resonance (CMR) in patients with suspected myocarditis. However, there are currently no data on the potential influence of slice orientation on the diagnostic performance of CMR. Thus, we compared the diagnostic performance of global myocardial T1 and extracellular volume (ECV) values to differentiate patients with myocarditis from healthy individuals between different slice orientations.MethodsThis study included 48 patients with clinically defined myocarditis and 13 healthy controls who underwent CMR at 1.5 T. A modified Look-Locker inversion-recovery (MOLLI) sequence was used for T1 mapping before and 15 min after administration of 0.075 mmol/kg Gadolinium-BOPTA. T1 mapping was performed on three short and on three long axes slices, respectively. Native T1, post-contrast T1 and extracellular volume (ECV) −BOPTA maps were calculated using a dedicated plug-in written for the OsiriX software and compared between the mean value of three short-axes slices (3SAX), the central short-axis (1SAX), the mean value of three long-axes slices (3LAX), the four-chamber view (4CH), the three-chamber view (3CH) and the two-chamber view (2CH).ResultsThere were significantly lower native T1 values on 3LAX (1081 ms (1037–1131 ms)) compared to 3SAX (1107 ms (1069–1143 ms), p = 0.0022) in patients with myocarditis, but not in controls (1026 ms (1009–1059 ms) vs. 1039 ms (1023–1055 ms), p = 0.2719). The areas under the curve (AUC) to discriminate between myocarditis and healthy controls by native myocardial T1 were 0.85 (p < 0.0001) on 3SAX, 0.85 (p < 0.0001) on 1SAX, 0.76 (p = 0.0002) on 3LAX, 0.70 (p = 0.0075) on 4CH, 0.72 (p = 0.0020) on 3CH and 0.75 (p = 0.0003) on 2CH. The AUCs for ECV-BOPTA were 0.83 (p < 0.0001) on 3 SAX, 0.82 (p < 0.0001) on 1SAX, 0.77 (p = 0.0005) on 3LAX, 0.71 (p = 0.0079) on 4CH, 0.69 (p = 0.0371) on 3CH and 0.75 (p = 0.0006) on 2CH.ConclusionNative T1 and ECV-BOPTA on short axes slices provide a better diagnostic performance in myocarditis than long axes slices since long axes slices seem to underestimate native myocardial T1 in myocarditis. T1 mapping in suspected myocarditis can be restricted to a single mid-ventricular short-axis slice without a significant loss in diagnostic performance.     

Evidence for a persistent sodium conductance in neurons from the nucleus prepositus hypoglossi

Intracellular recordings were made from 39 neurons in a slice preparation of the prepositus hypoglossi nucleus from guinea pigs. Morphological characteristics were confirmed by dying neurons with Lucifer yellow. The neurons were spontaneously active, firing in the range of 8–50 spikes/s. Spike duration was short (0.32 ms) and the spikes were followed by fast and slow afterhyperpolarizations. The current vs frequency relationship was linear during steady state firing, but showed dual firing ranges corresponding to the first, third and fifth interspike interval. The instantaneous frequency of the first few interspike intervals could reach 500 spikes/s. Depolarizing and hyperpolarizing responses to square pulses displayed initial sag and rebound responses sensitive to extracellular Cs⁺, pharmacologically classifying the responses as a result of a Q-like current. Substitution of Ca²⁺ in the medium with the inorganic calcium blockers Mn²⁺ or Co²⁺ resulted in oscillatory firing, depolarizing excursions being sensitive to tetrodotoxin (TTX). Mn²⁺ or Co²⁺ in combination with extracellular Cs⁺ elicited TTX-sensitive plateau potentials, blocked in Na⁺-free solution. In conclusion, the prepositus neurons displayed spontaneous activity in the slice preparation and active membrane properties above as well as below the threshold of the action potential. In addition, the prepositus neurons possess a persistent sodium conductance that can be uncovered by inorganic calcium blockers. It may be involved in sustaining the spontaneous discharge.     

Possible mechanism for species difference on the toxicity of pivalic acid between dogs and rats

In a high dose toxicity study of pivalic acid (PA), PA caused skeletal muscle disorder in dog, and a significant increase of pivaloyl carnitine (PC) was observed in canine muscle, but not in rat muscle. In order to understand species difference of the toxicity of PA, we compared the in vitro metabolism of PA among dog, rat and rabbit, especially focussing on the carnitine conjugate. Canine muscle showed low, but significant carnitine conjugating activity, while that of rat was negligible. Canine kidney mitochondria had significant activity in the pivaloyl CoA synthesis (7 nmol/mg protein/h), but muscle mitochondria showed only trace activity. Both kidney and muscle mitochondria displayed similar carnitine acyltransferase activity (2-3 nmol/mg protein/h) towards pivaloyl CoA. On the other hand, with respect to the activity of carnitine acyltransferase in the reverse direction using PC as substrate, canine muscle mitochondria showed higher activity than that of kidney mitochondria. This means that PC is not the final stable metabolite, but is converted easily to pivaloyl CoA in canine muscle. These results suggest one of the possible mechanisms for canine selective muscle disorder to be as follows. Only canine muscle can metabolize PA to its carnitine conjugate slowly, but significantly. In canine muscle, PC is not the final stable metabolite; it is easily converted to pivaloyl CoA. As carnitine conjugation is thought to be the only detoxification metabolic route in canine muscle, under certain circumstances such as carnitine deficiency, the risk of exposure with toxic pivaloyl CoA might increase and the CoASH pool in canine muscle might be exhausted, resulting in toxicity in canine muscle.     

Calcium-activated hyperpolarizations in neurons of the mediolateral part of the lateral septum: intracellular studies from guinea pig brain slices

Intracellular recordings were used to study the afterpotentials that followed a single spike and trains of spikes in class A neurons (n=85) of the mediolateral part of the lateral septum (LSml) of the guinea pig in in vitro slices. Following a single spike, LSml neurons (n=56) developed a slow afterhyperpolarization (sAHP), called early sAHP. These sAHP did not sum; other LSml neurons (n=8) showed a depolarizing afterpotential (DAP) that summed. Twenty-one neurons did not exhibit an afterpotential. Following a train of spikes, LSml neurons (n=79) developed a long-lasting sAHP, called late sAHP; these sAHP summed. Both the DAP and the early and late sAHP were markedly suppressed in amplitude by addition of Co²⁺ but persisted in the presence of tetrodotoxin (TTX). Increase in external K⁺ markedly depressed the early and late sAHP. Apamin and d-tubocurarine selectively blocked early sAHP, with no effect on late sAHP. These results indicate that the early and late sAHP are mainly generated by an activation of two types of Ca²⁺-dependent K⁺ conductances, with different time courses and pharmacological properties. In LSml neurons, late sAHP mediates the long-term adaptation of repetitive firing.