Elevation of Basal Protein Kinase C Activity Increases Ethanol Sensitivity of GABAA Receptors in Rat Hippocampal CA1 Pyramidal Neurons

Abstract: The ability of ethanol to enhance GABA_A receptor function remains controversial; conflicting observations have been made even in the same brain region, and when using apparently similar methodologies. In this study we characterized a single protocol variable, the initial incubation temperature of brain slices, that had dramatic effects on the ethanol sensitivity of GABA_A inhibitory postsynaptic currents (IPSCs) recorded from rat hippocampal CA1 pyramidal neurons. Incubation of hippocampal slices at relatively low temperatures (11–15°C) immediately after slice preparation significantly affected a number of physiological and biochemical parameters. Such slices showed a decrease in extracellular inhibitory postsynaptic potential amplitude, a significant increase in the ethanol sensitivity of GABA_A IPSCs in CA1 pyramidal neurons, no change in pentobarbital or flunitrazepam potentiation of IPSCs, and an increase in basal protein kinase C (PKC) activity relative to slices incubated at 31–33°C. In addition, the increase in ethanol sensitivity of GABA_A IPSCs was blocked by chelerythrine, a selective inhibitor of PKC. These results suggest that differences in hippocampal slice incubation protocols may have contributed to the disparate results of previous investigations of ethanol modulation of GABA_A receptor-mediated synaptic transmission in the rat hippocampus. In addition, these findings provide further evidence that PKC activity positively modulates the interaction between ethanol and GABA_A receptors in the mammalian brain.     

Gabapentin produces PKA-dependent pre-synaptic inhibition of GABAergic synaptic transmission in LC neurons following partial nerve injury in mice

We have previously demonstrated that gabapentin supraspinally activates the descending noradrenergic system to ameliorate pain hypersensitivity in mice with partial nerve ligation. To clarify the supraspinal mechanism of action of gabapentin, whole-cell patch-clamp recordings were performed on locus coeruleus (LC) neurons in brainstem slices prepared from mice after peripheral nerve injury or mice subjected to a sham-operation, and the effects of gabapentin in the modulation of synaptic transmission were studied. Bath application of gabapentin (10, 30 and 100 μM) in a concentration-dependent manner reduced the GABA_A receptor-mediated inhibitory post-synaptic currents (IPSCs) in slices prepared from partially nerve-ligated mice, whereas glutamate-mediated excitatory post-synaptic currents were hardly affected. By contrast, gabapentin did not reduce IPSCs in slices taken from mice given a sham operation. Although gabapentin altered neither the amplitude nor the frequency of miniature IPSCs, it reduced IPSCs together with an increase in the paired-pulse ratio, suggesting that gabapentin acts on the pre-synaptic GABAergic nerve terminals in the LC. As the protein kinase A (PKA) inhibitor H-89 but not the protein kinase C inhibitor chelerythrine abolished the inhibitory action of gabapentin on IPSCs, PKA-mediated phosphorylation seems to be important for supraspinal gabapentin responsiveness in neuropathic conditions. Together, gabapentin generates PKA-dependent pre-synaptic inhibition of GABAergic synaptic transmission, and thereby removes the inhibitory influence on LC neurons only under neuropathic pain states. These findings provide crucial evidence of how supraspinally acting gabapentin recruits the descending noradrenergic system.     

Differential pharmacological properties of GABAA receptors in axon terminals and soma of dentate gyrus granule cells

Although it has been well established that GABA_A receptors are molecular targets of a variety of allosteric modulators, such as benzodiazepines, the pharmacological properties of presynaptic GABA_A receptors are poorly understood. In this study, the effects of diazepam and Zn²⁺ on presynaptic GABA_A receptors have been investigated by measuring the GABA_A receptor-mediated facilitation of spontaneous glutamate release in mechanically dissociated rat CA3 pyramidal neurons. Diazepam significantly enhanced the muscimol-induced facilitation (particularly at submicromolar concentrations) of spontaneous glutamate release and shifted the concentration–response relationship for muscimol toward the left, whereas Zn²⁺ (≤ 100 μM) had little effect on the muscimol-induced facilitation of spontaneous glutamate release. In contrast, Zn²⁺ significantly suppressed the muscimol-induced currents mediated by GABA_A receptors expressed on dentate gyrus granule cells, which are parent neurons of mossy fibers, whereas the effect of diazepam on GABA_A receptors expressed on dentate gyrus granule cells was lesser than that on presynaptic GABA_A receptors. The results suggest that the pharmacological properties of GABA_A receptors differ considerably between presynaptic (axon terminals) and somatic regions in the same granule cell and that presynaptic GABA_A receptors should be considered as one of the important pharmacological targets of many drugs affecting GABA_A receptors.     

Rapid Down-Regulation of GABAA Receptors in the Gerbil Hippocampus Following Transient Cerebral Ischemia

Abstract: During transient cerebral ischemia, there is a temporary and robust accumulation of extracellular GABA in the hippocampus. We examined whether the acute exposure of GABA_A/benzodiazepine receptors to high concentrations of GABA early after ischemia results in receptor down-regulation as observed in vitro. Gerbils were killed 30 and 60 min following a 5-min bilateral carotid occlusion, and their brains were prepared for receptor autoradiography. The hydrophilic GABA_A receptor antagonist [³H]SR-95531 and the hydrophobic benzodiazepine agonist [³H]flunitrazepam were used to distinguish between cell surface and internalized receptors. Ischemia significantly decreased [³H]SR-95531 binding in hippocampal areas CA1 and CA3 and in the dentate gyrus 30 min after ischemia. Scatchard analysis in area CA1 revealed that ischemia decreased the B _max as low as 44%. The affinity of the remaining sites was increased substantially (72% decrease in K _D). As expected, there were no changes in the binding of [³H]flunitrazepam to hippocampus in the early postischemic period because the benzodiazepine could bind to both internalized receptors and those on the cell surface. We hypothesize that prolonged exposure (∼30–45 min) of GABA_A receptors to high concentrations of synaptic GABA in vivo causes receptor down-regulation, perhaps via receptor internalization.     

Leptin induces a novel form of NMDA receptor-dependent long-term depression

It is becoming apparent that the hormone leptin plays an important role in modulating hippocampal function. Indeed, leptin enhances NMDA receptor activation and promotes hippocampal long-term potentiation (LTP). Furthermore, obese rodents with dysfunctional leptin receptors display impairments in hippocampal synaptic plasticity. Here we demonstrate that under conditions of enhanced excitability (evoked in Mg2+-free medium or following blockade of GABA(A) receptors), leptin induces a novel form of long-term depression (LTD) in area CA1 of the hippocampus. Leptin-induced LTD was markedly attenuated in the presence of D-(-)-2-Amino-5-Phosphonopentanoic acid (D-AP5), suggesting that it is dependent on the synaptic activation of NMDA receptors. In addition, low-frequency stimulus-evoked LTD occluded the effects of leptin. In contrast, metabotropic glutamate receptors (mGluRs) did not contribute to leptin-induced LTD as mGluR antagonists failed to either prevent or reverse this process. The signalling mechanisms underlying leptin-induced LTD were independent of the Ras-Raf-mitogen-activated protein kinase signalling pathway, but were markedly enhanced following inhibition of either phosphoinositide 3-kinase or protein phosphatases 1 and 2A. These data indicate that under conditions of enhanced excitability, leptin induces a novel form of homosynaptic LTD, which further underscores the proposed key role for this hormone in modulating NMDA receptor-dependent hippocampal synaptic plasticity.     

Role of PI3K and PKB/Akt in acute natriuretic and NO-mimetic effects of leptin

Apart from controlling energy balance, leptin, a peptide hormone secreted by white adipose tissue, is also involved in the regulation of cardiovascular function. Previous studies have documented that leptin stimulates natriuresis and nitric oxide (NO) production, but the mechanism of these effects is incompletely elucidated. We examined whether phosphoinositide 3-kinase (PI3K) and its downstream effector, protein kinase B/Akt are involved in acute natriuretic and NO-mimetic effects of leptin in anaesthetized rats. Leptin (1 mg/kg i.v.) induced a marked increase in natriuresis and this effect was abolished by pretreatment with either wortmannin (15 μg/kg) or LY294002 (0.6 mg/kg), two structurally different PI3K inhibitors. Moreover, leptin increased plasma concentration and urinary excretion of NO metabolites, nitrites + nitrates (NO_x), and of NO second messenger, cyclic GMP. In addition, leptin increased NO_x and cGMP in aortic tissue. The stimulatory effect of leptin on NO_x and cGMP was prevented by PKB/Akt inhibitor, triciribine, but not by either wortmannin or LY294002. Triciribine had no effect on leptin-induced natriuresis. Leptin stimulated Akt phosphorylation at Ser⁴⁷³ in aortic tissue but not in the kidney. These results suggest that leptin-induced natriuresis is mediated by PI3K but not Akt, whereas NO-mimetic effect of leptin results from PI3K-independent stimulation of Akt.     

Gephyrin expression and clustering affects the size of glutamatergic synaptic contacts

We have recently shown that disrupting the expression and post-synaptic clustering of gephyrin in cultured hippocampal pyramidal cells, by either gephyrin RNAi (RNA interference) or over-expression of a dominant negative gephyrin-enhanced green fluorescent protein (EGFP) fusion protein, leads to decreased number of post-synaptic gephyrin and GABA_A receptor clusters and to reduced GABAergic innervation of these cells. On the other hand, increasing gephyrin expression led to a small increase in the number of gephyrin and GABA_A receptor clusters and to little or no effect on GABAergic innervation. We are now reporting that altering gephyrin expression and clustering affects the size but not the density of glutamatergic synaptic contacts. Knocking down gephyrin with gephyrin RNAi, or preventing gephyrin clustering by over-expression of the dominant negative gephyrin-enhanced green fluorescent protein fusion protein, leads to larger post-synaptic PSD-95 clusters and larger pre-synaptic glutamatergic terminals. On the other hand, over-expression of gephyrin leads to slightly smaller PSD-95 clusters and pre-synaptic glutamatergic terminals. The change in size of PSD-95 clusters were accompanied by a parallel change in the size of NR2-NMDA receptor clusters. It is concluded that the levels of expression and clustering of gephyrin, a protein that concentrates at the post-synaptic complex of the inhibitory synapses, not only has homotypic effects on GABAergic synaptic contacts, but also has heterotypic effects on glutamatergic synaptic contacts. We are proposing that gephyrin is a counterpart of the post-synaptic glutamatergic scaffold protein PSD-95 in regulating the number and/or size of the excitatory and inhibitory synaptic contacts.     

Applicability of Peak-Scaled Nonstationary Fluctuation Analysis to the Study of Inhibitory Synaptic Transmission in Hippocampal Cultures

At present, there are no direct methods to determine the number of synaptic receptor-related channels activated in the course of synaptic transmission (N) or a value of the single-channel conductance (γ). Peak-scaled nonstationary fluctuation analysis (PS NSFA) should be considered the most well-developed indirect approach used for estimating these parameters. Despite the relatively wide using of this approach for the analysis of various synaptic currents, some aspects of possible errors that can occur in the course of data acquisition or their subsequent processing have not been studied. We examined in detail the problem of applicability of PS NSFA in the study of spontaneous and evoked GABA-ergic inhibitory postsynaptic currents (IPSCs). IPSCs were recorded using a dual patch-clamp technique from hippocampal neurons growing in low-density cultures. Parameters of the recorded IPSCs and values for different components of GABA-ergic synaptic transmission reported earlier were used for simulations and PS-NSFA analysis. In Monte Carlo computer simulations of evoked IPSCs, the influence of series resistance, background noise, asynchronicity of transmitter release, GABA_A channel properties, dendritic attenuation, and instrumental filtering on γ estimates obtained by PS NSFA was examined. We concluded that the γ and, consequently, N values may be satisfactorily estimated by the suggested approach using spontaneous and evoked IPSCs recorded in inhibitory synaptic connections in hippocampal cultures within a wide range of experimental conditions. We also estimated the mean of the single-channel conductance of synaptic GABA_A receptors in neurons from primary hippocampal cultures and found that this value (29 ± 5 pS) agrees well with the high conductance of single synaptic GABA_A receptors observed in acute hippocampal slices. This indicates that dissociated cultures are an adequate model for studying the properties of synaptic GABA_A receptors. Neirofiziologiya/Neurophysiology, Vol. 37, No. 4, pp. 379–388, July–August, 2004.     

Leptin: a diverse regulator of neuronal function

It is well documented that leptin is a circulating hormone that plays a key role in regulating food intake and body weight via its actions on specific hypothalamic nuclei. However, leptin receptors are widely expressed in the CNS, in regions not generally associated with energy homeostasis, such as the hippocampus, cortex and cerebellum. Moreover, evidence is accumulating that leptin has widespread actions in the brain. In particular, recent studies have demonstrated that leptin markedly influences the excitability of hippocampal neurons via its ability to activate large conductance Ca(2+)-activated K(+) (BK) channels, and also to promote long-term depression of excitatory synaptic transmission. Here, we review the evidence supporting a role for this hormone in regulating hippocampal excitability.     

An investigation into signal transduction mechanisms involved in insulin-induced long-term depression in the CA1 region of the hippocampus

Recent work has demonstrated that brief application of insulin to hippocampal slices can induce a novel form of long-term depression (insulin-LTD) in the CA1 region of the hippocampus; however, the molecular details of how insulin triggers LTD remain unclear. Using electrophysiological and biochemical approaches in the hippocampal slices, we show here that insulin-LTD (i) is specific to 3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor- but not NMDA receptor-mediated synaptic transmission; (ii) is induced and expressed postsynaptically but does not require the activation of ionotropic and metabotropic glutamate receptors; (iii) requires a concomitant Ca(2+) influx through l-type voltage-activated Ca(2+) channels (VACCs) and the release of Ca(2+) from intracellular stores; (iv) requires the series of protein kinases, including protein tyrosine kinase (PTK), phosphatidylinositol 3-kinase (PI3K), and protein kinase C (PKC); (v) is mechanistically distinct from low-frequency stimulation-induced LTD (LFS-LTD) and independent on protein phosphatase 1/2 A (PP1/2 A) and PP2B activation; (vi) is dependent on a rapamycin-sensitive local translation of dendritic mRNA, and (vii) is associated with a persistent decrease in the surface expression of GluR2 subunit. These results suggest that a PI3K/PKC-dependent insulin signaling, which controls postsynaptic surface AMPA receptor numbers through PP-independent endocytosis, may be a major expression mechanism of insulin-LTD in hippocampal CA1 neurons.     

Leptin reverses long-term potentiation at hippocampal CA1 synapses

The hormone leptin crosses the blood brain barrier and regulates numerous neuronal functions, including hippocampal synaptic plasticity. Here we show that application of leptin resulted in the reversal of long-term potentiation (LTP) at hippocampal CA1 synapses. The ability of leptin to depotentiate CA1 synapses was concentration-dependent and it displayed a distinct temporal profile. Leptin-induced depotentiation was not associated with any change in the paired pulse facilitation ratio or the coefficient of variance, indicating a post-synaptic locus of expression. Moreover, the synaptic activation of NMDA receptors was required for leptin-induced depotentiation as the effects of leptin were blocked by the competitive NMDA receptor antagonist, D-aminophosphovaleric acid (D-AP5). The signaling mechanisms underlying leptin-induced depotentiation involved activation of the calcium/calmodulin-dependent protein phosphatase, calcineurin, but were independent of c- jun NH₂ terminal kinase. Furthermore, leptin-induced depotentiation was accompanied by a reduction in α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor rectification indicating that loss of glutamate receptor 2 (GluR2)-lacking AMPA receptors underlies this process. These data indicate that leptin reverses hippocampal LTP via a process involving calcineurin-dependent internalization of GluR2-lacking AMPA receptors which further highlights the key role for this hormone in regulating hippocampal synaptic plasticity and neuronal development.     

Evidence for Functionally Distinct Subclasses of γ-Aminobutyric Acid Receptors in Rabbit Retina

Abstract: γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the mammalian retina, where it serves many roles in establishing complex response characteristics of ganglion cells. We now provide biochemical and physiological evidence that at least three subclasses of GABA receptors (A1, A2, and B) contribute to different types of synaptic integration. Receptor binding studies indicate that approximately three-fourths of the total number of [³H]GABA binding sites in retina are displaced by the GABA_A receptor antagonist, bicuculline, whereas one-fourth are displaced by the GABA-B receptor agonist, baclofen. GABA_A receptors can be described by a three-site binding model with K_D values of 19 n M , 122 n M , and 5.7 μ M . Benzodiazepines and barbiturates potentiate binding to the GABA_A site, which suggests that significant numbers of GABA_A receptors are coupled to regulatory sites for these compounds and thus are classified as GABA_A1 receptors. The response to pentobarbital appears to involve a conversion of low-affinity sites to higher-affinity sites, and is reflected in changes in the densities of sites at different affinities. Functional studies were used to establish which of the different receptor subclasses regulate release from cholinergic amacrine cells. Our results show that GABA suppresses light-evoked [³H]acetylcholine release via GABA_A2 receptors not coupled to a benzodiazepine or barbiturate regulatory site, and enhances release via GABA_B receptors. GABA_A1 sites do not appear to control acetylcholine release in rabbit retina.     

A structural model for phosphorylation control of Dictyostelium myosin II thick filament assembly

Deletion of the synapsin I genes, encoding one of the major groups of proteins on synaptic vesicles, in mice causes late onset epileptic seizures and enhanced experimental temporal lobe epilepsy. However, mice lacking synapsin I maintain normal excitatory synaptic transmission and modulation but for an enhancement of paired-pulse facilitation. To elucidate the cellular basis for epilepsy in mutants, we examined whether the inhibitory synapses in the hippocampus from mutant mice are intact by electrophysiological and morphological means. In the cultured hippocampal synapses from mutant mice, repeated application of a hypertonic solution significantly suppressed the subsequent transmitter release, associated with an accelerated vesicle replenishing time at the inhibitory synapses, compared with the excitatory synapses. In the mutants, morphologically identifiable synaptic vesicles failed to accumulate after application of a hypertonic solution at the inhibitory preterminals but not at the excitatory preterminals. In the CA3 pyramidal cells in hippocampal slices from mutant mice, inhibitory postsynaptic currents evoked by direct electrical stimulation of the interneuron in the striatum oriens were characterized by reduced quantal content compared with those in wild type. We conclude that synapsin I contributes to the anchoring of synaptic vesicles, thereby minimizing transmitter depletion at the inhibitory synapses. This may explain, at least in part, the epileptic seizures occurring in the synapsin I mutant mice.     

Insulin modulates hippocampal activity-dependent synaptic plasticity in a N-methyl-d-aspartate receptor and phosphatidyl-inositol-3-kinase-dependent manner

Insulin and its receptor are both present in the central nervous system and are implicated in neuronal survival and hippocampal synaptic plasticity. Here we show that insulin activates phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB), and results in an induction of long-term depression (LTD) in hippocampal CA1 neurones. Evaluation of the frequency-response curve of synaptic plasticity revealed that insulin induced LTD at 0.033 Hz and LTP at 10 Hz, whereas in the absence of insulin, 1 Hz induced LTD and 100 Hz induced LTP. LTD induction in the presence of insulin required low frequency synaptic stimulation (0.033 Hz) and blockade of GABAergic transmission. The LTD or LTP induced in the presence of insulin was N-methyl-d-aspartate (NMDA) receptor specific as it could be inhibited by alpha-amino-5-phosphonopentanoic acid (APV), a specific NMDA receptor antagonist. LTD induction was also facilitated by lowering the extracellular Mg(2+) concentration, indicating an involvement of NMDA receptors. Inhibition of PI3K signalling or discontinuing synaptic stimulation also prevented this LTD. These results show that insulin modulates activity-dependent synaptic plasticity, which requires activation of NMDA receptors and the PI3K pathway. The results obtained provide a mechanistic link between insulin and synaptic plasticity, and explain how insulin functions as a neuromodulator.     

Leptin excites basolateral amygdala principal neurons and reduces food intake by LepRb-JAK2-PI3K-dependent depression of GIRK channels

Leptin is an adipocyte-derived hormone that modulates food intake, energy balance, neuroendocrine status, thermogenesis, and cognition. Whereas a high density of leptin receptors has been detected in the basolateral amygdala (BLA) neurons, the physiological functions of leptin in the BLA have not been determined yet. We found that application of leptin excited BLA principal neurons by activation of the long form leptin receptor, LepRb. The LepRb-elicited excitation of BLA neurons was mediated by depression of the G protein-activated inwardly rectifying potassium (GIRK) channels. Janus Kinase 2 (JAK2) and phosphoinositide 3-kinase (PI3K) were required for leptin-induced excitation of BLA neurons and depression of GIRK channels. Microinjection of leptin into the BLA reduced food intake via activation of LepRb, JAK2, and PI3K. Our results may provide a cellular and molecular mechanism to explain the physiological roles of leptin in vivo.     

Leptin and its role in hippocampal synaptic plasticity

It is well documented that the hormone leptin plays a pivotal role in regulating food intake and body weight via its hypothalamic actions. However, leptin receptors are expressed throughout the brain with high levels found in the hippocampus. Evidence is accumulating that leptin has widespread actions on CNS function and in particular learning and memory. Recent studies have demonstrated that leptin-deficient or-insensitive rodents have impairments in hippocampal synaptic plasticity and in spatial memory tasks performed in the Morris water maze. Moreover, direct administration of leptin into the brain facilitates hippocampal long-term potentiation (LTP), and improves memory performance in mice. There is also evidence that, at the cellular level, leptin has the capacity to convert hippocampal short-term potentiation (STP) into LTP, via enhancing NMDA receptor function. Recent data indicates that leptin can also induce a novel form of NMDA receptor-dependent hippocampal long-term depression. Here, we review the evidence implicating a key role for the hormone leptin in modulating hippocampal synaptic plasticity and discuss the role of lipid signaling cascades in this process.     

Chronic Intermittent Ethanol Treatment in Rats Increases GABAA Receptor α4-Subunit Expression: Possible Relevance to Alcohol Dependence

Abstract: Chronic administration of ethanol to rats on an intermittent regimen, for 60 repeated intoxicating doses and repeated withdrawal episodes, results in a long-lasting kindling phenomenon. This involves an increasing severity of withdrawal, including a reduced threshold to seizures produced by the GABA_A antagonist, pentylenetetrazol. We have shown previously that muscimol-evoked ³⁶Cl⁻ efflux and paired-pulse inhibition (involving GABA_A-mediated recurrent inhibition) were decreased persistently in the CA1 region of hippocampal slices from chronic intermittent ethanol (CIE)-treated rats. We now report elevated levels of mRNA in forebrain for the α4 subunit of the GABA_A receptor (GABAR), considered to be a constituent of pharmacologically and physiologically novel subtypes of GABARs. Using in situ hybridization with digoxigenin-labeled RNA probes, we show that at 2 days withdrawal, 60-dose CIE leads to a significant 30% increase in α4 subunit mRNA levels in the dentate gyrus, 46% increase in the CA3, and 26% increase in the CA1 regions. In contrast, there was no significant change in the mRNAs for the α5 subunit or glutamic acid decarboxylase 67 in the same regions. This study suggests that GABAR subunit-selective alterations occur after CIE treatment, possibly resulting in the alteration of the subunit composition of GABARs, with presumably altered physiological functions. This plasticity of GABARs may contribute to the increased withdrawal severity, reduced hippocampal inhibition, and increased seizure susceptibility of this animal model of human alcohol dependence.     

Inhibition of Neuroblastoma Cell Phosphatidylinositol 3-Kinase by CDP-Diacylglycerol and Phosphatidate

Abstract: Phosphatidylinositol (PI) 3-kinase is activated by a variety of agents, including various growth factors, and has been proposed to play a role in initiation of cell growth, proliferation, and differentiation. We here investigate the effect of various membrane lipids on PI 3-kinase immunopurified from human SH-SY5Y neuroblastoma cells. CDP-diacylglycerol (CDP-DAG) inhibited PI 3-kinase activity with an IC₅₀ of 6 µ M . Phosphatidate (PA) was also inhibitory (IC₅₀ = 38 µ M ) as was lysophosphatidate. Neither DAG nor any of the other phospholipids examined affected PI 3-kinase activity. The results offer the possibility that CDP-DAG or PA at critical membrane sites may exert functionally significant metabolic regulation at the point of convergence of the PI 3-kinase-directed and the PI 4-kinase-directed phosphoinositide signal transduction pathways.     

青蒿素经PI3K/Akt通路改善突触可塑性减轻糖尿病小鼠认知障碍

目的 本研究旨在阐明青蒿素对II型糖尿病（T2DM）小鼠认知功能障碍的改善作用及其机制。方法 C57BL/6J小鼠单次腹腔注射STZ（100 mg/kg）后联合高脂饲料喂养建立T2DM模型。T2DM小鼠随后腹腔注射青蒿素（40 mg/kg/d）或等体积溶剂。干预4周后，新物体识别、Y迷宫和Morris水迷宫实验检测小鼠的学习和记忆能力。蛋白质印迹法（Western blot）检测海马PI3K、Akt、磷酸化Akt、SYN和PSD-95蛋白的表达。透射电镜观察海马CA1区突触密度和突触超微结构改变。结果 与模型组相比，青蒿素干预组T2DM小鼠的认知功能显著改善，海马中PI3K和磷酸化Akt水平升高，SYN和PSD-95蛋白表达增加，CA1区神经元丢失减少。此外，青蒿素干预组小鼠CA1区的突触密度、PSD-95和突触界面曲率增加，突触间隙宽度减小。结论 青蒿素可能通过激活海马PI3K/Akt途径增强突触可塑性，从而减轻T2DM小鼠认知功能障碍；青蒿素有望成为治疗糖尿病性认知功能障碍的新型药物。