Chronic sleep deprivation exacerbates cognitive and pathological impairments in APP/PS1/tau triple transgenic Alzheimer's disease model mice / 生理学报

Sleep exerts important functions in the regulation of cognition and emotion. Recent studies have found that sleep disorder is one of the important risk factors for Alzheimer's disease (AD), but the effects of chronic sleep deprivation on the cognitive functions of AD model mice and its possible mechanism are still unclear. In the present study, 8-month-old male APP/PS1/tau triple transgenic AD model (3xTg-AD) mice and wild type (WT) mice (n = 8 for each group) were subjected to chronic sleep deprivation by using the modified multiple platform method, with 20 h of sleep deprivation each day for 21 days. Then, open field test, elevated plus maze test, sugar water preference test, object recognition test, Y maze test and conditioned fear memory test were performed to evaluate anxiety- and depression-like behaviors, and multiple cognitive functions. In addition, the immunohistochemistry technique was used to observe pathological characteristics in the hippocampus of mice. The results showed that: (1) Chronic sleep deprivation did not affect anxiety- (P = 0.539) and depression-like behaviors (P = 0.874) in 3xTg-AD mice; (2) Chronic sleep deprivation exacerbated the impairments of object recognition memory (P < 0.001), working memory (P = 0.002) and the conditioned fear memory (P = 0.039) in 3xTg-AD mice; (3) Chronic sleep deprivation increased amyloid β (Aβ) deposition (P < 0.001) and microglial activation (P < 0.001) in the hippocampus of 3xTg-AD mice, without inducing abnormal tau phosphorylation and neurofibrillary tangles. These results indicate that chronic sleep deprivation exacerbates the impairments of recognition memory, working memory and conditioned fear memory in 3xTg-AD mice by aggravating Aβ deposition and the excessive activation of microglia in the hippocampus.

Sex Differences in Neuropathology and Cognitive Behavior in APP/PS1/tau Triple-Transgenic Mouse Model of Alzheimer's Disease / 神经科学通报·英文版

Alzheimer's disease (AD) is the most common form of dementia among the elderly, characterized by amyloid plaques, neurofibrillary tangles, and neuroinflammation in the brain, as well as impaired cognitive behaviors. A sex difference in the prevalence of AD has been noted, while sex differences in the cerebral pathology and relevant molecular mechanisms are not well clarified. In the present study, we systematically investigated the sex differences in pathological characteristics and cognitive behavior in 12-month-old male and female APP/PS1/tau triple-transgenic AD mice (3×Tg-AD mice) and examined the molecular mechanisms. We found that female 3×Tg-AD mice displayed more prominent amyloid plaques, neurofibrillary tangles, neuroinflammation, and spatial cognitive deficits than male 3×Tg-AD mice. Furthermore, the expression levels of hippocampal protein kinase A-cAMP response element-binding protein (PKA-CREB) and p38-mitogen-activated protein kinases (MAPK) also showed sex difference in the AD mice, with a significant increase in the levels of p-PKA/p-CREB and a decrease in the p-p38 in female, but not male, 3×Tg-AD mice. We suggest that an estrogen deficiency-induced PKA-CREB-MAPK signaling disorder in 12-month-old female 3×Tg-AD mice might be involved in the serious pathological and cognitive damage in these mice. Therefore, sex differences should be taken into account in investigating AD biomarkers and related target molecules, and estrogen supplementation or PKA-CREB-MAPK stabilization could be beneficial in relieving the pathological damage in AD and improving the cognitive behavior of reproductively-senescent females.

The improvement effect of scFv17 on the gait of triple-transgenic mice / 中国应用生理学杂志

OBJECTIVE@#To observe the gait changes of Alzheimer's disease PS1M146V/APPswe/tauP301L triple-transgenic (3xTg-AD) mice and to investigate the improvement effect of single chain variable domain antibody fragment 17 (scFv17) on the gait.@*METHODS@#In the present study, a selection of 6-month-old 3xTg-AD mice (=18) and C57BL/6 wild-type mice (=24) was performed. First, we observed their gait changes and found that the gait of 12-month-old 3xTg-AD mice was severely damaged. Then, the two groups of mice were randomly divided into four groups:WT+PBS(=12), WT+scFv17(=12), 3xTg-AD+PBS(=9) and 3xTg-AD+scFv17(=9). The gait behavior test and pathological test were performed after 12 weeks'continuous administration of scFv17 (1.5 mg/kg) or an equal volume of PBS (0.01 mol/L) by nasal gavage twice a week.@*RESULTS@#Compared with the same month old wild type mice, the rear track width of 12 month old 3xTg-AD mice was increased(<0.01), swing time percent was decreased (<0.01), stance time percent was increased(<0.01), so the ability of movement coordination and balance was seriously damaged. ScFv17 could improve the coordination and balance ability of 12 month old 3xTg-AD mice(<0.01). The morphological structure of 3xTg-AD mice cerebellar Purkinje cells was improved. The treatment of scFv17 increased the Nissl body number of the cerebellar Purkinje cells of 3xTg-AD mice (<0.01). scFv17 reduced the amyloid β protein (Aβ) plaques in the cerebellar cortex of 3xTg-AD mice (<0.01), and scFv17 reduced the intracellular neurofibrillary tangles (NFT) of the cerebellar Purkinje cells of the 3xTg-AD mice (<0.01).@*CONCLUSIONS@#The coordination and balance ability of 3xTg-AD mice was significantly impaired. ScFv17 can improve gait behaviour in the 3xTg-AD significantly.The mechanism may be related to the improvement of the structure and protein function of cerebellar Purkinje cells, and the eliminating of the Aβ plaques and the neurofibrillary tangles.

Amyloid β protein injection into medial septum impairs hippocampal long-term potentiation and cognitive behaviors in rats / 生理学报

The specific loss of cholinergic neurons and the progressive deficits of cognitive function are the most primary characteristics of Alzheimer's disease (AD). Although the neurotoxicity of amyloid β protein (Aβ) in AD has been investigated extensively, it is still unclear whether the Aβ aggregated in the medial septum (MS), a major cholinergic nucleus projecting to the hippocampus, could affect hippocampal synaptic plasticity and further impair the memory behaviors. The present study investigated the effects of Aβ injection into the MS on hippocampal long-term potentiation (LTP) and cognitive behaviors of rats by using Morris water maze (MWM), Y maze and in vivo hippocampal LTP recording. The effects of kainic acid (KA), an agent with specific neurotoxicity to GABAergic neurons, were also observed. The results showed that: (1) Intra-MS injection of Aβ, not KA, impaired spatial learning and memory of rats in classical and reversal MWM tests; (2) Both Aβ and KA impaired novelty-seeking behavior of rats in Y maze; (3) Intra-MS injection of Aβ, not KA, suppressed in vivo hippocampal LTP in the CA1 region of rats; (4) Both Aβ and KA did not affect the motor ability in behavioral tests and the hippocampal paired-pulse facilitation (PPF) in electrophysiological recording. These results indicate that intra-MS injection of Aβ could impair spatial memory, cognitive flexibility and exploratory motivation, as well as hippocampal LTP in rats, suggesting that the cholinergic neurons in the MS and the septo-hippocampal projection could be important targets of neurotoxic Aβ, and the specific damage of cholinergic neurons in the MS is likely responsible for the impairments of hippocampal synaptic plasticity and cognitive function in AD.

Application of wireless neuronal recording system in fear conditioning of Alzheimer's disease mice - hippocampal Theta oscillation observation / 生理学报

APP/PS1/tau triple transgenic (3xTg) mouse is a classical animal model of Alzheimer's disease (AD), which has abnormalities in recognition and electrophysiological properties at early 6-month-old age. However, few studies were performed by using simultaneously recording cognitive behavior and brain electrical activity in the conscious 3xTg mice. By using a new wireless recording system, we recorded hippocampal Theta oscillations in 3xTg mice during the process of fear conditioning test. The results showed that: (1) in training session, no significant difference in the fear behavior and hippocampal Theta activity was found between 3xTg mice and WT mice; (2) in test session, 3xTg mice showed a significant decrease in freezing ratio compared with WT mice when they were exposed to conditioning stimulus (CS); (3) the 3xTg mice showed lower peak power in Theta oscillation in both Pre-CS and CS duration compared with WT mice; (4) CS effectively induced an increase in the peak frequency of Theta oscillation in WT mice, but not in 3xTg mice. These results indicated that the impairment of cognition behavior in 3xTg mice was accompanied with the decreased peak power and peak frequency of Theta oscillation in the hippocampus, suggesting that a decline in Theta oscillation might be involved in the impairments of the fear conditioning, and the enhanced hippocampal Theta oscillation may be beneficial for improving AD cognitive function.

GLP-1/GIP/Gcg receptor Triagonist improves the cognitive behaviors in triple-transgenic mice of Alzheimer's disease / 生理学报

Alzheimer's disease (AD) is a progressively neurodegenerative disorder, which seriously affects human health but is still irreversible up to now. Recent studies indicate that type 2 diabetes mellitus (T2DM) is an important risk factor for AD, and the drugs used for treatment of T2DM have shown some neuroprotective effects in the treatment of AD. Glucagon-like peptide-1 (GLP-1)/ glucose-dependent insulinotropic polypeptide (GIP)/glucagon (Gcg) receptor Triagonist is a new monomeric polypeptide equally activating the GLP-1/GIP/Gcg receptors, which is built on the basis of GLP-1/Gcg receptor coagonist core sequence, and incorporated with partial amino acids of GIP. Recently, the Triagonist has been reported to be effective in alleviating diabetic complications in rodent models of obesity. The present study observed for the first time the cognitive improvement effects of the Triagonist in the triple-transgenic AD mice (3xTg-AD) by using multiple behavioral techniques, and explored its probable molecular mechanisms using ELISA and Western blot. The results showed that the chronic treatment with the Triagonist (i.p.) significantly reversed the impairments in working memory of 3xTg-AD mice, with an obvious increase in the percentage of correct spontaneous alternation in the Y maze; the Triagonist treatment also improved long-term spatial memory and re-learning ability of 3xTg-AD mice in classical Morris water maze and reverse water maze tests, with decreased escape latency in under water platform tests and increased swimming time in probe tests. ELISA and Western blot experiments showed that the Triagonist up-regulated the levels of cAMP, PKA and p-CREB in the hippocampus of 3xTg-AD mice. These results indicate that GLP-1/GIP/Gcg receptor Triagonist can improve the cognitive behaviors in 3xTg-AD mice, and the up-regulation of hippocampal cAMP/PKA/CREB signal pathway may mediate the neuroprotection of the Triagonist, suggesting that the GLP-1/GIP/Gcg receptor Triagonist may be a novel therapeutic strategy for the treatment of AD.

Real-time measurement of Caflux in hippocampal slice with non-invasive micro-test technique / 生理学报

The deposition of amyloid-β protein (Aβ) in the brain is the most important pathological feature of Alzheimer's disease (AD). The mechanism of Aβ neurotoxicity may be closely related to the disturbance of intracellular Cahomeostasis. Non-invasive micro-test technique (NMT) is a novel technique developed in recent years, which can be used to directly record transmembrane ion influx and efflux in a non-contact way by detecting the diffusion potentials outside of the membrane. The present study examined the effects of Aβpretreatment on glutamate (Glu)-induced Cainflux and low [Ca] solution-induced Caefflux in the hippocampal slices of C57BL/6 mice using NMT. The results showed that: (1) acute administration of Glu (2.5, 5, 10 mmol/L) evoked a persistent transmembrane Cainflux in hippocampal CA1 neurons, with a rapid onset and subsequent decay; (2) pretreatment with Aβ dose-dependently increased the average rate of Cainflux induced by Glu during the initial 5 min, which was blocked by NMDA receptor antagonist D-APV; (3) perfusion with low [Ca] artificial cerebrospinal fluid (aCSF) induced a continuous Caefflux, which was mostly blocked by KB-R7943, a specific antagonist of Na/Caexchanger; (4) Aβpretreatment partially inhibited the low [Ca] aCSF-induced Caefflux. These results indicate that Aβ not only facilitates Cainflux but also inhibits Caefflux, which jointly contribute to the Aβ-induced intracellular Caoverload; the potentiation of Aβ on Glu excitotoxicity is mainly mediated by NMDA receptors, while the target for Aβ to affect Caefflux was mainly Na/Caexchanger. NMT showed multiple advantages in detecting transmembrane Caflux in brain slices, such as non-invasiveness to target cells, fast, convenient and real-time acquisition of Caflux. Therefore, this study provided new experimental evidence for Aβ-induced Caoverload, as well as a novel application for NMT in measuring transmembrane Caflux of neurons in the brain.

Neuroprotective effects of a novel antidiabetic drug (D-Ser2)Oxm on amyloid β protein-induced cytotoxicity / 生理学报

The accumulation and neurotoxicity of amyloid β protein (Aβ) in the brain is one of major pathological hallmarks of Alzheimer's disease (AD). The effective drugs against Aβ have been still deficient up to now. According to a most recent study, (D-Ser2) Oxm, a new antidiabetic drug, not only improves the disorders in plasma glucose and insulin in type 2 diabetes mellitus (T2DM) rats, but also exerts positive effects on hippocampal neurogenesis and synaptogenesis. However, it is still unclear whether (D-Ser2)Oxm can directly protect cultured neurons against Aβ1-42-induced cytotoxicity. In the present study, we investigated the neuroprotective effects of (D-Ser2)Oxm on the cultured primary hippocampal neurons by testing the cell viability, neuronal apoptosis, mitochondrial membrane potential and intracellular calcium concentration. The results showed that treatment with (D-Ser2)Oxm effectively reversed Aβ1-42-induced decline in cell viability (P < 0.001), and this protective effect could be inhibited by the pretreatment with exendin(9-39), a GLP-1 receptor blocker. (D-Ser2)Oxm treatment also decreased Aβ1-42-induced neuronal early apoptosis and down-regulated apoptotic protein caspase3. Meantime, (D-Ser2)Oxm treatment inhibited Aβ1-42-induced [Ca(2+)]i elevation, mitochondrial membrane potential depolarization, and glycogen synthase kinase-3β (GSK3β) activation. These results suggest that (D-Ser2)Oxm can protect hippocampal neurons against Aβ1-42-induced cytotoxicity and this effect may be related to activation of GLP-1 receptors, regulation of intracellular calcium homeostasis and stabilization of mitochondrial membrane potential.

Effects of rapamycin on amyloid β-protein induced impairments of working memory and synaptic plasticity in rats / 中国应用生理学杂志

<p><b>OBJECTIVE</b>The present study investigated the effects of rapamycin on Aβ1-42-induced deficits in working memory and synaptic plasticity.</p><p><b>METHODS</b>After bilateral hippocampal injection of Aβ1-42 and rapamycinin rats, spontaneous alternation in Y-maze and in vivo hippocampal long-term potentiation (LTP) of rats were recorded. All data were analized by two-way repeated measures analysis of variance (ANOVA).</p><p><b>RESULTS</b>(Hippocampal injection of Aβ1-42 alone impaired working memory of rats; (2) Rapamycin did not affect working memory of rats, but alleviated Aβ1-42-induced working memory deficits, compared with Aβ1-42 alone group; (Aβ1-42 remarkably suppressed in vivo hippocampal LTP of fEPSPs in the CA1 region; (4) Pretreatment with rapamycin prevented Aβ1-42-induced suppression of LTP.</p><p><b>CONCLUSION</b>These data indicates that rapamycin could protect against Aβ1-42-induced impairments in working memory and synaptic plasticity in rats.</p>

Amyloid β protein suppresses hippocampal theta rhythm and induces behavioral disinhibition and spatial memory deficit in rats / 生理学报

Hippocampal neuronal network oscillation is closely related to the memory, anxiety and behavioral inhibition of mammalian. The cognitive decline and behavioral disinhibition in the patients with Alzheimer's disease (AD) may be relevant to amyloid β protein (Aβ)-induced impairment in hippocampal neuronal cooperative activity. However, it is not well known whether intrahippocampal injection of Aβ could induce behavioral disinhibition and neuronal network disorder, as well as cognition decline in animals. In the present study, we observed the effects of intracerebral injection of Aβ(1-42) on the spatial memory and behavioral inhibition of rats by using Morris water maze and elevated plus-maze tests. Further, we analyzed hippocampal theta rhythm by recording hippocampal local field potential. The results showed that: (1) bilateral hippocampal injection of Aβ(1-42) reduced the anxious behavior of rats, with a significant behavioral disinhibition in the elevated plus-maze test, representing as an increase in the mean entering times and mean residence time in the open arm; (2) Aβ(1-42) injection resulted in a significant impairment of spatial memory in rats, with significantly increased mean escape latencies in hidden platform test; (3) Aβ(1-42) disrupted the induction of theta rhythm induced by tail pinch, with a significant reduction in the peak power, not the peak power frequency of the theta rhythm. These experimental results indicate that intrahippocampal injection of Aβ(1-42) can induce behavioral disinhibition and theta rhythm suppression, as well as spatial memory impairment in rats, which suggests that the cognition deficits and behavior impairments in AD are probably associated with the Aβ-induced disruption of hippocampal theta rhythm and consequent down-regulation of synaptic plasticity.

Brain-derived neurotrophic factor prevents against amyloid beta protein-induced impairment of hippocampal in vivo long-term potentiation in rats / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore the effects of brain-derived neurotrophic factor (BDNF) pretreatment on beta amyloid protein (Abeta) induced impairment of in vivo hippocampal long-term potentiation (LTP) in the CA1 region of rats.</p><p><b>METHODS</b>Thirty-six adult male SD rats were randomly divided into six groups (n = 6): control, Abeta25-35, BDNF, (0.02 microg, 0.1 microg, 0.5 microg) BDNF + Abeta25-35. A self-made hippocampal local drug delivery catheter and a parallel bound stimulating/recording electrode were used to deliver drugs/stimulation and record field excitatory post-synaptic potentials (fEPSPs) in the hippocampal CA1 region of rats. High-frequency stimulation (HFS) was used to induce in vivo LTP.</p><p><b>RESULTS</b>(1) Abeta25-35 (2 nmol) injection into CA1 region of rats did not affect the baseline fEPSPs, but inhibited the HFS-induced LTP significantly (P < 0.01). (2) Hippocampal CA1 injection of BDNF (0.1 microg) alone did not affect the baseline fEPSPs and HFS-induced LTP. (3) Compared with Abeta25-35 alone group, the averaged amplitude of LTP in BDNF (0.1 microg and 0.5 microg) plus Abeta25-35 groups significantly increased at 0 min, 30 min, and 60 min after HFS (P < 0.01), indicating that pretreatment with BDNF effectively protected against the Abeta,25-35 induced depression of LTP in a dose-dependent manner.</p><p><b>CONCLUSION</b>Intrahippocampal injection of BDNF can protect against the Abeta25-35-induced LTP impairment, suggesting that the up-regulation of BDNF in the brain could maintain the normal hippocampal synaptic plasticity and may contribute to the improvement of learning and memory in Alzheimer's (AD) disease patients.</p>

Oxidative stress and Alzheimer's disease / 生理学报

Alzheimer's disease (AD) has become one of the most important and most interesting focuses in the field of medical and scientific research. Up to now, the pathogenesis of AD has not been completely clarified. However, the high-density of amyloid β-protein (Aβ) in senile plaques of AD brain and the neurotoxicity of Aβ have been indisputable facts. The mechanisms underlying Aβ neurotoxicity are very complicated, involving calcium overload, inflammation, ion channel dysfunction, oxidative stress and so on. Among all of those, the mechanism of oxidative stress in Aβ neurotoxicity and the experimental progress of antioxidants in AD treatment have been widely reported in recent years. This review mainly discussed current research progresses on the oxidative stress of Aβ, so as to provide readers with some clues to the antioxidant therapy of AD.

Gly14-humanin protects against Aβ₃₁₋₃₅-induced impairment of spatial learning and memory in rats / 生理学报

Amyloid β protein (Aβ) is closely involved in the pathogenesis of Alzheimer's disease (AD), and one of the main strategies for AD treatment is antagonizing the neurotoxicity of Aβ or even clearing the Aβ deposited in the brain. The present study was aimed to observe the effects of intrahippocampal injection of Aβ₃₁₋₃₅ on the spatial learning and memory of rats by using Morris water maze technique, and explore the neuroprotective effects and possible mechanism of [Gly14]-humanin (HNG) against Aβ-induced deficits in learning behavior. The results showed that bilateral intrahippocampal injection of 2.0 nmol Aβ₃₁₋₃₅ significantly increased the mean traveled distance of rats in searching for the hidden underwater platform and decreased the distance percentage in the target quadrant in probe test after withdrawal of platform, whereas pretreatment with HNG (0.2 nmol and 2.0 nmol) suppressed Aβ₃₁₋₃₅-induced increase in the traveled distance and decrease in swimming distance percentage. Application of Genistein (40 nmol), a specific tyrosine kinase inhibitor, almost completely blocked the antagonistic effects of HNG against Aβ₃₁₋₃₅. These results indicate that HNG can dose-dependently prevent against Aβ₃₁₋₃₅-induced impairment in spatial learning and memory of rats, and the neuroprotective effects of HNG might involve the activation of endogenous tyrosine kinase pathway, suggesting that up-regulation of the tyrosine kinase signaling by using HNG might be of great significance for the improvement of cognitive function in AD.

Glucagon-like peptide 1: a novel therapeutic strategy for Alzheimer's disease / 生理学报

There is a close correlation between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) in the course of pathophysiological processes. The neuroprotective action of glucagon-like peptide 1 (GLP-1), a latest drug for clinical treatment of T2DM, is being more deeply investigated at present, and a novel therapeutic strategy for AD with GLP-1 has been proposed boldly. This review mainly discussed the correlation of pathogenesis between T2DM and AD, the synthesis and secretion of GLP-1, the distribution and physiological effects of GLP-1 receptor in the brain, and the progresses on the study of GLP-1 in the treatment of AD.

Effects of amyloid β-protein on hippocampal long-term potentiation / 生理学报

The accumulation of amyloid β-protein (Aβ) plaques is identified as a major pathological feature of Alzheimer's disease (AD). Recent studies show that soluble species of Aβ are involved in the early memory dysfunction long before neurodegenerative changes. However, the mechanism underlying the neurotoxicity of soluble Aβ is still unclear. Long-term potentiation (LTP) has been thought as an important cellular model of synaptic plasticity for many years. The studies on the hippocampal LTP and Aβ, especially those using AD transgenic models, provided more evidence for the Aβ-induced dysfunction of learning and memory. Based on the recent researches on AD, this article reviewed the effects of Aβ, especially soluble Aβ and its active fragments, on the hippocampal LTP. The possible mechanisms by which Aβ impairs hippocampal LTP are also discussed.

Involvement of protein tyrosine kinases in β-amyloid protein-induced suppression of long-term potentiation in the rat hippocampal CA1 region in vivo / 生理学报

Although the impairing effects of beta-amyloid (Aβ) protein on synaptic plasticity and cognitive function have been widely reported, the mechanisms underlying the neurotoxicity of Aβ are still not well known. The present study observed the effects of intracerebroventricular (i.c.v.) injection of both Aβ(23-35) and genistein (a specific tyrosine kinase inhibitor at high concentration) on the hippocampal long-term potentiation (LTP) in the CA1 region, and investigated its possible protein tyrosine kinase (PTK) mechanism. Male Wistar rats were surgically prepared for acute LTP recordings in vivo. Two parallel bond electrodes for stimulating and recording were simultaneously inserted into the right hippocampus of rats. The field excitatory postsynaptic potentials (fEPSPs), paired-pulse facilitation (PPF) and high-frequency stimuli (HFS)-induced LTP were recorded by delivering test stimuli, paired pulses and HFS to the Schaffer-collateral/commissural pathway. The results showed that: (1) i.c.v. injection of Aβ(23-35) did not affect the baseline synaptic transmission, but significantly suppressed the HFS-induced LTP, with a decreased average amplitude of fEPSPs [(129.2+/-6.7)% in 10 nmol Aβ(23-35) group; (110.6+/-8.6)% in 20 nmol Aβ(23-35) group; P<0.01] at 1 h post-HFS when compared to that in the control group [(163.1+/-8.1)%]; (2) Similarly, i.c.v. injection of genistein (200 nmol) did not change the basic synaptic transmission, but significantly suppressed HFS-induced LTP, with the similar average amplitude of fEPSPs [(114.0+/-7.2)%] at 1 h post-HFS to that in 20 nmol Aβ(23-35) group; (3) Co-application of Aβ(23-35) (20 nmol) and genistein (200 nmol) caused no additive suppression of LTP, and the average amplitude of fEPSPs was (113.0+/-8.8)% at 1 h post-HFS, showing no significant difference when compared with that in Aβ(23-35) or genistein alone groups (P>0.05); (4) There was no significant change in the PPF following genistein and Aβ(23-35) alone or co-injection (P>0.05). These experimental results indicate that i.c.v. injection of Aβ(23-35) can significantly suppress the HFS-induced LTP in the CA1 area of rat hippocampus in vivo, implying that the Aβ deposited in the brain of patients with Alzheimer's disease may impair the function of learning and memory by suppressing the hippocampal LTP. The facts that the extent of inhibition of Aβ(23-35) and genistein on LTP was similar and no further potentiation of the suppression was observed when Aβ(23-35) and genistein were co-applied suggest that PTK is probably involved in the Aβ-induced suppression of hippocampal LTP.

Involvement of nicotinic acetylcholine receptors in amyloid β-fragment-induced intracellular Ca(2+) elevation in cultured rat cortical neurons / 生理学报

The amyloid β-protein (Aβ)-induced disturbance of intracellular calcium homeostasis has been regarded as the final route whereby Aβ insults neurons. However, the mechanism of Aβ-induced Ca(2+) overloading is still unclear so far. Especially, it remains to be clarified whether nicotinic acetylcholine receptors (nAChRs) are involved in the Aβ-induced elevation of intracellular calcium concentration ([Ca(2+)](i)). In the present study, we observed the effects of Aβ fragments 25-35 (Aβ(25-35)) and 31-35 (Aβ(31-35)) on [Ca(2+)](i) in primary cultured rat cortical neurons using laser-scanning confocal calcium imaging technique, and investigated its probable cholinergic mechanism. The results showed that: (1) Both Aβ(25-35) and Aβ(31-35) induced similar and significant [Ca(2+)](i) elevation in a concentration-dependent manner, and no statistical difference was found between the effects of both peptides; (2) The reverse peptide of Aβ(31-35), i.e. Aβ(35-31), had no effect on [Ca(2+)](i) elevation; (3) Mecamylamine (MCA), a non-specific nAChRs antagonist, significantly and dose-dependently blocked the [Ca(2+)](i) elevation induced by Aβ(25-35) or Aβ(31-35) (4) Dihydro-β-erythroidine (D-β-E), a specific α4β2 subtype nAChRs antagonist, also significantly inhibited the [Ca(2+)](i) elevation induced by Aβ(25-35) and Aβ(31-35), but the effect was weaker than the effect of MCA at the same concentration. These results indicate that Aβ(31-35) may be a shorter active sequence in full length of Aβ molecule, and the overactivation of nAChRs, including α4β2 subtype, may be, at least partly, responsible for the Aβ-induced elevation of [Ca(2+)](i) in cultured rat cortical neurons. Thus, the present study suggests a new potential target of Aβ in the brain, and provides a new insight into the mechanisms by which Aβ impairs the cognitive function in Alzheimer's disease.

Electrophysiological characteristics of central neuronal dendrites and roles of dendritic back-propagating action potentials in modifications of synaptic plasticity / 生理学报

For expressing the condolences on the passing away of Dr. Hsiang-Tung Chang, one of the distinguished members of the Chinese Academia of Sciences, the pioneer studies on cortical dendritic potentials that Dr. Chang carried out in the 1950s and the prosperous progresses since then, especially, concerning the modifications of synaptic plasticity by the dendritic back-propagating action potentials were briefly reviewed.

Recordings of long-term potentiation in rat hippocampal CA1 area with an electrodes-binding technique in vivo / 中国应用生理学杂志

<p><b>AIM</b>To study the feasibility of long-term potentiation(LTP) recording in the CA1 area of the rat in vivo with electrodes-binding technique.</p><p><b>METHODS</b>Anesthetizing Wistar rats with urethane and fixing the animal on the stereotaxic device for acute surgery; implanting cannula into lateral cerebral ventricle; inserting self-made bound stimulating/recording electrodes into hippocampal CA1 area; recording basal field excitatory postsynaptic potential (fEPSP) and tetanus-induced long term potentiation (LTP).</p><p><b>RESULTS</b>fEPSPs were reliably induced by using the stimulating/recording electrodes-binding technique, and the appearance rate of fEPSP was nearly 100%; basal fEPSP recording was very stable, lasting for long time enough to finish all experiment; high frequency stimulation (HFS) successfully induced LTP, which maintained more than three hours, the inductivity is about 67%; paired-pulse facilitation (PPF) recording was also stable; intracerebroventricular (i c v) injection of amyloid beta suppressed HFSinduced LTP evidently.</p><p><b>CONCLUSION</b>The electrodes-binding technique for recording hippocampal LTP in vivo is quite simple and convenient. The experimental resource can be saved, and the rates of fEPSP appearance and LTP induction are kept high. Therefore, it is promising for this technique to be one electrophysiological auxiliary method in the research of learning and memory.</p>

ATP-sensitive potassium channels and endogenous adenosine are involved in spinal antinociception produced by locus coeruleus stimulation / 生理学报

It has been known that locus coeruleus (LC) stimulation suppresses nociceptive discharges of the thalamic parafascicular (PF) neurons through the spinally descending adrenergic terminals which inhibit the transmission of nociceptive signals in the spinal dorsal horn. This experimental model was used in the present study to analyze the detailed processes that happened in the dorsal horn following norepinephrine release by preemptive intrathecal (i.t.) administration of related drugs in lightly urethane-anesthetized rats. The results showed that: (1) LC stimulation significantly inhibited the noxiously-evoked discharges of PF neurons; (2) the LC stimulation-produced antinociception in PF neurons could be blocked either by i.t. glibenclamide, an ATP-sensitive potassium (K(+)(ATP)) channel blocker, or by i.t. aminophylline, an adenosine receptor antagonist; (3) nociceptive discharges of PF neurons were also suppressed both by i.t. 5 -N-ethylcarboxamido-adenosine (NECA, an adenosine receptor agonist) and by i.t. nicorandil (a K(+)(ATP) channel opener); and (4) i.t. aminophylline blocked the suppression of PF nociceptive discharges induced by i.t. nicorandil, while i.t. glibenclamide showed no effect on the suppression of nociceptive discharges induced by i.t. NECA. These results suggest that: (1) K(+)(ATP) channels and endogenous adenosine may be involved in the mediation of spinal antinociception induced by descending adrenergic fibers originating from the LC; and (2) the opening of K(+)(ATP) channels precedes the release of adenosine in the cascade of mediation.