Dopamine Receptors Differentially Control Binge Alcohol Drinking-Mediated Synaptic Plasticity of the Core Nucleus Accumbens Direct and Indirect Pathways.

Binge alcohol drinking, a behavior characterized by rapid repeated alcohol intake, is most prevalent in young adults and is a risk factor for excessive alcohol consumption and alcohol dependence. Although the alteration of synaptic plasticity is thought to contribute to this behavior, there is currently little evidence that this is the case. We used drinking in the dark (DID) as a model of binge alcohol drinking to assess its effects on spike timing-dependent plasticity (STDP) in medium spiny neurons (MSNs) of the core nucleus accumbens (NAc) by combining patch-clamp recordings with calcium imaging and optogenetics. After 2 weeks of daily alcohol binges, synaptic plasticity was profoundly altered. STDP in MSNs expressing dopamine D1 receptors shifted from spike-timing-dependent long-term depression (tLTD), the predominant form of plasticity in naive male mice, to spike-timing-dependent long-term potentiation (tLTP) in DID mice, an effect that was totally reversed in the presence of 4 µm SCH23390, a dopamine D1 receptor antagonist. In MSNs presumably expressing dopamine D2 receptors, tLTP, the main form of plasticity in naive mice, was inhibited in DID mice. Interestingly, 1 µm sulpiride, a D2 receptor antagonist, restored tLTP. Although we observed no alterations of AMPA and NMDA receptor properties, we found that the AMPA/NMDA ratio increased at cortical and amygdaloid inputs but not at hippocampal inputs. Also, DID effects on STDP were accompanied by lower dendritic calcium transients. These data suggest that the role of dopamine in mediating the effects of binge alcohol drinking on synaptic plasticity of NAc MSNs differs markedly whether these neurons belong to the direct or indirect pathways.SIGNIFICANCE STATEMENT We examined the relationship between binge alcohol drinking and spike timing-dependent plasticity in nucleus accumbens (NAc) neurons. We found that repeated drinking bouts modulate differently synaptic plasticity in medium spiny neurons of the accumbens direct and indirect pathways. While timing-dependent long-term depression switches to long-term potentiation (LTP) in the former, timing-dependent LTP is inhibited in the latter. These effects are not accompanied by changes in AMPA and NMDA receptor properties at cortical, amygdaloid, and hippocampal synapses. Interestingly, dopamine D1 and D2 receptor antagonists have opposite effects on plasticity. Our data show that whether core NAc medium spiny neurons belong to the direct or indirect pathways determines the form of spike timing-dependent plasticity (STDP), the manner by which STDP responds to binge alcohol drinking, and its sensitivity to dopamine receptor antagonists.

The Sub1 nuclear protein protects DNA from oxidative damage.

Reactive oxygen species are a by-product of aerobic metabolism that can damage lipid, proteins, and nucleic acids. Oxidative damage to DNA is especially critical, because it can lead to cell death or mutagenesis. Previously we reported that the yeast sub1 deletion mutant is sensitive to hydrogen peroxide treatment and that the human SUB1 can complement the sensitivity of the yeast sub1 mutant. In this study, we find that Sub1 protects DNA from oxidative damage in vivo and in vitro. We demonstrate that transcription of SUB1 mRNA is induced by oxidative stress and that the sub1Δ mutant has an increased number of chromosomal DNA strand breaks after peroxide treatment. We further demonstrate that purified Sub1 protein can protect DNA from oxidative damage in vitro, using the metal ion catalyzed oxidation assay.

Machine learning was used to predict risk factors for distant metastasis of pancreatic cancer and prognosis analysis.

BACKGROUND: The mechanisms of distant metastasis in pancreatic cancer (PC) have not been elucidated, and this study aimed to explore the risk factors affecting the metastasis and prognosis of metastatic patients and to develop a predictive model. METHOD: Clinical data from patients meeting criteria from 1990 to 2019 were obtained from the Surveillance, Epidemiology, and End Results (SEER) database, and two machine learning methods, random forest and support vector machine, combined with logistic regression, were used to explore risk factors influencing distant metastasis and to create nomograms. The performance of the model was validated using calibration curves and ROC curves based on the Shaanxi Provincial People's Hospital cohort. LASSO regression and Cox regression models were used to explore the independent risk factors affecting the prognosis of patients with distant PC metastases. RESULTS: We found that independent risk factors affecting PC distant metastasis were: age, radiotherapy, chemotherapy, T and N; the independent risk factors for patient prognosis were: age, grade, bone metastasis, brain metastasis, lung metastasis, radiotherapy and chemotherapy. CONCLUSION: Together, our study provides a method for risk factors and prognostic assessment for patients with distant PC metastases. The nomogram we developed can be used as a convenient individualized tool to facilitate aid in clinical decision making.

New rules governing synaptic plasticity in core nucleus accumbens medium spiny neurons.

The nucleus accumbens is a forebrain region responsible for drug reward and goal-directed behaviors. It has long been believed that drugs of abuse exert their addictive properties on behavior by altering the strength of synaptic communication over long periods of time. To date, attempts at understanding the relationship between drugs of abuse and synaptic plasticity have relied on the high-frequency long-term potentiation model of T.V. Bliss & T. Lømo [(1973) Journal of Physiology, 232, 331-356]. We examined synaptic plasticity using spike-timing-dependent plasticity, a stimulation paradigm that reflects more closely the in vivo firing patterns of mouse core nucleus accumbens medium spiny neurons and their afferents. In contrast to other brain regions, the same stimulation paradigm evoked bidirectional long-term plasticity. The magnitude of spike-timing-dependent long-term potentiation (tLTP) changed with the delay between action potentials and excitatory post-synaptic potentials, and frequency, whereas that of spike-timing-dependent long-term depression (tLTD) remained unchanged. We showed that tLTP depended on N-methyl-d-aspartate receptors, whereas tLTD relied on action potentials. Importantly, the intracellular calcium signaling pathways mobilised during tLTP and tLTD were different. Thus, calcium-induced calcium release underlies tLTD but not tLTP. Finally, we found that the firing pattern of a subset of medium spiny neurons was strongly inhibited by dopamine receptor agonists. Surprisingly, these neurons were exclusively associated with tLTP but not with tLTD. Taken together, these data point to the existence of two subgroups of medium spiny neurons with distinct properties, each displaying unique abilities to undergo synaptic plasticity.

Silicon functionalization expands the repertoire of Si-rhodamine fluorescent probes.

Fluorescent dyes such as rhodamines are widely used to assay the activity and image the location of otherwise invisible molecules. Si-rhodamines, in which the bridging oxygen of rhodamines is replaced with a dimethyl silyl group, are increasingly the dye scaffold of choice for biological applications, as fluorescence is shifted into the near-infrared while maintaining high brightness. Despite intense interest in Si-rhodamines, there has been no exploration of the scope of silicon functionalization in these dyes, a potential site of modification that does not exist in conventional rhodamines. Here we report a broad range of silyl modifications that enable brighter dyes, further red-shifting, new ways to modulate fluorescence, and the introduction of handles for dye attachment, including fluorogenic labeling agents for nuclear DNA, SNAP-tag and HaloTag labeling. Modifications to the bridging silicon are therefore of broad utility to improve and expand the applications of all Si-dyes.

Novel neuroprotectant chiral 3-n-butylphthalide inhibits tandem-pore-domain potassium channel TREK-1.

AIM: To study the effects of 3-n-butylphthalide (NBP) on the TREK-1 channel expressed in Chinese hamster ovary (CHO) cells. METHODS: Whole-cell patch-clamp recording was used to record TREK-1 channel currents. The effects of varying doses of l-NBP on TREK-1 currents were also observed. Current-clamp recordings were performed to measure the resting membrane potential in TREK-1-transfected CHO (TREK-1/CHO) and wild-type CHO (Wt/CHO) cells. RESULTS: l-NBP (0.01-10 µmol/L) showed concentration-dependent inhibition on TREK-1 currents (IC(50)=0.06±0.03 µmol/L), with a maximum current reduction of 70% at a concentration of 10 µmol/L. l-NBP showed a more potent inhibition on TREK-1 current than d-NBP or dl-NBP. This effect was partially reversed upon washout and was not voltage-dependent. l-NBP 10 µmol/L elevated the membrane potential in TREK-1/CHO cells from -55.3 mV to -42.9 mV. However, it had no effect on the membrane potential of Wt/CHO cells. CONCLUSION: 1-NBP potently inhibited TREK-1 current and elevated the membrane potential, which may contribute to its neuroprotective activity.

Bioluminescence imaging in mice with synthetic luciferin analogues.

Luciferase enzymes from bioluminescent organisms can be expressed in mice, enabling these rodents to glow when treated with a corresponding luciferin substrate. Light emission occurs where the expression of the genetically-encoded luciferase overlaps with the biodistribution of the administered small molecule luciferin. Here we discuss differences between firefly luciferin analogues for bioluminescence imaging, focusing on transgenic and adeno-associated virus (AAV)-transduced mice.

The Sodium Channel ß4 Auxiliary Subunit Selectively Controls Long-Term Depression in Core Nucleus Accumbens Medium Spiny Neurons.

Voltage-gated sodium channels are essential for generating the initial rapid depolarization of neuronal membrane potential during action potentials (APs) that enable cell-to-cell communication, the propagation of signals throughout the brain, and the induction of synaptic plasticity. Although all brain neurons express one or several variants coding for the core pore-forming sodium channel α subunit, the expression of the ß (ß1-4) auxiliary subunits varies greatly. Of particular interest is the ß4 subunit, encoded by the Scn4b gene, that is highly expressed in dorsal and ventral (i.e., nucleus accumbens - NAc) striata compared to other brain regions, and that endows sodium channels with unique gating properties. However, its role on neuronal activity, synaptic plasticity, and behaviors related to drugs of abuse remains poorly understood. Combining whole-cell patch-clamp recordings with two-photon calcium imaging in Scn4b knockout (KO) and knockdown mice, we found that Scn4b altered the properties of APs in core accumbens medium spiny neurons (MSNs). These alterations are associated with a reduction of the probability of MSNs to evoke spike-timing-dependent long-term depression (tLTD) and a reduced ability of backpropagating APs to evoke dendritic calcium transients. In contrast, long-term potentiation (tLTP) remained unaffected. Interestingly, we also showed that amphetamine-induced locomotor activity was significantly reduced in male Scn4b KO mice compared to wild-type controls. Taken together, these data indicate that the Scn4b subunit selectively controls tLTD by modulating dendritic calcium transients evoked by backpropagating APs.

The origin of glutamatergic synaptic inputs controls synaptic plasticity and its modulation by alcohol in mice nucleus accumbens.

It is widely accepted that long-lasting changes of synaptic strength in the nucleus accumbens (NAc), a brain region involved in drug reward, mediate acute and chronic effects of alcohol. However, our understanding of the mechanisms underlying the effects of alcohol on synaptic plasticity is limited by the fact that the NAc receives glutamatergic inputs from distinct brain regions (e.g., the prefrontal cortex (PFCx), the amygdala and the hippocampus), each region providing different information (e.g., spatial, emotional and cognitive). Combining whole-cell patch-clamp recordings and the optogenetic technique, we examined synaptic plasticity, and its regulation by alcohol, at cortical, hippocampal and amygdala inputs in fresh slices of mouse tissue. We showed that the origin of synaptic inputs determines the basic properties of glutamatergic synaptic transmission, the expression of spike-timing dependent long-term depression (tLTD) and long-term potentiation (LTP) and long-term potentiation (tLTP) and their regulation by alcohol. While we observed both tLTP and tLTD at amygadala and hippocampal synapses, we showed that cortical inputs only undergo tLTD. Functionally, we provide evidence that acute Ethyl Alcohol (EtOH) has little effects on higher order information coming from the PFCx, while severely impacting the ability of emotional and contextual information to induce long-lasting changes of synaptic strength.

BK channels mediate dopamine inhibition of firing in a subpopulation of core nucleus accumbens medium spiny neurons.

Dopamine, a key neurotransmitter mediating the rewarding properties of drugs of abuse, is widely believed to exert some of its effects by modulating neuronal activity of nucleus accumbens (NAcc) medium spiny neurons (MSNs). Although its effects on synaptic transmission have been well documented, its regulation of intrinsic neuronal excitability is less understood. In this study, we examined the cellular mechanisms of acute dopamine effects on core accumbens MSNs evoked firing. We found that 0.5 µM A-77636 and 10 µM quinpirole, dopamine D1 (DR1s) and D2 receptor (D2Rs) agonists, respectively, markedly inhibited MSN evoked action potentials. This effect, observed only in about 25% of all neurons, was associated with spike-timing-dependent (STDP) long-term potentiation (tLTP), but not long-term depression (tLTD). Dopamine inhibits evoked firing by compromising subthreshold depolarization, not by altering action potentials themselves. Recordings in voltage-clamp mode revealed that all MSNs expressed fast (IA), slowly inactivating delayed rectifier (Idr), and large conductance voltage- and calcium-activated potassium (BKs) channels. Although A-77636 and quinpirole enhanced IA, its selective blockade by 0.5 µM phrixotoxin-1 had no effect on evoked firing. In contrast, exposing tissue to low TEA concentrations and to 10 µM paxilline, a selective BK channel blocker, prevented D1R agonist from inhibiting MSN firing. This result indicates that dopamine inhibits MSN firing through BK channels in a subpopulation of core accumbens MSNs exclusively associated with spike-timing-dependent long-term potentiation.

Potassium 2-(1-hydroxypentyl)-benzoate improves learning and memory deficits in chronic cerebral hypoperfused rats.

Potassium 2-(1-hydroxypentyl)-benzoate (dl-PHPB), the pre-drug of 3-n-butylphthalide (dl-NBP), had the significantly therapeutic effect on the acute cerebral ischemia. The present study was to investigate the effect of dl-PHPB on the cognitive deficits induced by chronic cerebral hypoperfusion. Rats were orally administered three doses of dl-PHPB (13, 39 and 129mg/kg), dl-NBP 100mg/kg, and piracetam 600mg/kg daily for 21 days after the bilateral permanent occlusion of the common carotid arteries. The results showed that dl-PHPB, dl-NBP and piracetam significantly improved the spatial learning and memory deficits, and the effectiveness of dl-PHPB at dose of 39mg/kg was strongest. Meanwhile, the drugs decreased superoxide dismutase activity, reduced lipid peroxide and astrocyte activation in the cortex of the hypoperfused rats. Furthermore, dl-PHPB markedly reduced white matter rarefaction. The results indicated that preventing neuropathological alterations, inhibiting oxidative damage and inflammatory reaction might contribute to the improvement of dl-PHPB on hypoperfusion-induced cognitive deficits. Therefore, dl-PHPB has therapeutic potential for the treatment of dementia caused by decrease of cerebral blood flow.

[Effects of ginkgo biloba extracts on NMDA-activated currents in acutely isolated rat hippocampal neurons].

AIM: To investigate effect of ginkgo biloba extract (GBE) on N-methyl-D-aspartate (NMDA)-activated currents (I(NMDA)) and evaluate further the modulatory effects of Micro-GBE/Nano-GBE. METHODS: By means of whole-cell patch clamp technique, NMDA-activated currents from acutely isolated rat hippocampal neurons were recored. RESULTS: The majority of the neurons examined (81.8%, 90/110) were sensitive to NMDA (1 mmol/L) and its co-agonist Gly (10 micromol/L). NMDA activated an inward current, which manifested apparent desensitization and could be blocked by its specific antagonist MK-801. After the neurons were treated with Micro/Nano GBE (0.1 mg/ml) followed by the application of NMDA (1 mmol/L) and Gly (10 micromol/L) for 30 s, it was show that NMDA-activated currents were obviously inhibited (P < 0.01, n = 8). The inhibitory rate were 40% +/- 17% and 64% +/- 15% respectively. It showed that the modulatory effect of Nano-GBE (dissolved in the stander extracellular solution) on NMDA-activated current was significantly higher than that of Micro-GBE (dissolved in DMSO) (P < 0.05). CONCLUSION: The inward currents activated by NMDA could be depressed by Micro-GBE and Nano-GBE. The modulatory effects of GBE on NMDA-activated current are expected to contribute to the neuroprotective effects of ginkgo biloba extracts. In addition, at the same concentration, the modulatory effect of Nano-GBE on NMDA-activated current is better than that of Micro-GBE.