Acute pentobarbital treatment impairs spatial learning and memory and hippocampal long-term potentiation in rats

Electroacupuncture Attenuates Anxiety-Like Behaviors in a Rat Model of Post-traumatic Stress Disorder: The Role of the Ventromedial Prefrontal Cortex

Electroacupuncture (EA) is a promising clinical approach to treating posttraumatic stress disorder (PTSD), yet the mechanisms whereby EA can alleviate anxiety and other PTSD symptoms have yet to be clarified. In the present report, rats underwent EA for 14 consecutive days following modified single prolonged stress (MSPS) exposure. These animals were then evaluated in open field and elevated plus maze tests (OFT and EPM), while Fos immunohistochemical staining was performed to assess ventromedial prefrontal cortex (vmPFC) functional activation. In addition, an extracellular recording and stimulation system was used to analyze vmPFC inputs into the ventral tegmental area (VTA) in these rats. Temporary vmPFC inactivation was further performed to assess whether this was sufficient to reverse the anxiolytic effects of EA. Overall, rats that underwent EA treatment spent more time in the central region (OFT) and the open arm (EPM) relative to MSPS model animals (P < 0.05). These MSPS model animals also exhibited significantly fewer activated Fos-positive nuclei in the vmPFC following behavioral testing, while EA was associated with a significant relative increase in c-Fos expression in this region. The transient inactivation of the vmPFC was sufficient to reverse the effects of EA treatment on anxiety-like behaviors in MSPS model rats. MSPS and SEA rats exhibiting no differences in bursting activity between baseline and vmPFC stimulation, whereas bursting activity rose relative to baseline upon ventral mPFC stimulation in EA treated and control rats. Together, these findings indicate that the vmPFC and its inputs into the VTA are functionally linked to the anxiolytic activity of EA, implicating this pathway in the EA-mediated treatment of PTSD.

Localized anesthesia of a specific brain region using ultrasound-responsive barbiturate nanodroplets

Background: Targeted neuromodulation is a valuable technique for the study and treatment of the brain. Using focused ultrasound to target the local delivery of anesthetics in the brain offers a safe and reproducible option for suppressing neuronal activity. Objective: To develop a potential new tool for localized neuromodulation through the triggered release of pentobarbital from ultrasound-responsive nanodroplets. Method: The commercial microbubble contrast agent, Definity, was filled with decafluorobutane gas and loaded with a lipophilic anesthetic drug, before being condensed into liquid-filled nanodroplets of 210 ± 80 nm. Focused ultrasound at 0.58 MHz was found to convert nanodroplets into microbubbles, simultaneously releasing the drug and inducing local anesthesia in the motor cortex of rats (n=8). Results: Behavioral analysis indicated a 19.1 ± 13% motor deficit on the contralateral side of treated animals, assessed through the cylinder test and gait analysis, illustrating successful local anesthesia, without compromising the blood-brain barrier. Conclusion: Pentobarbital-loaded decafluorobutane-core Definity-based nanodroplets are a potential agent for ultrasound-triggered and targeted neuromodulation.

Electroacupuncture reduces astrocyte number and oxidative stress in aged rats with surgery-induced cognitive dysfunction

Objectives

To investigate the effects of electroacupuncture in regulating astrocytes and oxidative stress in a rat model of postoperative cognitive dysfunction (POCD).

Methods

Male aged Sprague-Dawley rats were randomized to undergo left hepatic lobe resection to induce POCD, followed by either electroacupuncture or no treatment; or similar surgery without left lobe resection or electroacupuncture (sham). Postsurgical cognitive function, hippocampal astrocyte number and oxidative stress indicators were measured.

Results

At days 1, 3 and 7 following surgery, escape latency was significantly shorter and platform crossing frequency was increased with electroacupuncture versus other groups. At postoperative day 1, the electroacupuncture group showed significantly fewer glial fibrillary acidic protein (GFAP)-positive hippocampal astrocytes versus the POCD model group. In POCD rats, electroacupuncture significantly decreased serum S100 calcium binding protein B and neuron-specific enolase levels, and increased brain-derived neurotrophic factor and glial cell-derived neurotrophic factor levels, at days 1, 3 and 7. Electroacupuncture significantly attenuated the hippocampal POCD-induced increase in malondialdehyde and decreased superoxide dismutase levels at day 1 following surgery.

Conclusion

Electroacupuncture may improve cognitive function in rats with POCD by reducing hippocampal GFAP-positive astrocyte number and suppressing oxidative stress.

Capsaicin Attenuates Amyloid-β-Induced Synapse Loss and Cognitive Impairments in Mice

Alzheimer's disease (AD) is the most common cause of progressive cognitive impairment in the aged. The aggregation of the amyloid β-protein (Aβ) is a hallmark of AD and is linked to synapse loss and cognitive impairment. Capsaicin, a specific agonist of the transient receptor potential vanilloid 1 (TRPV1), has been proven to ameliorate stress-induced AD-like pathological and cognitive impairments, but it is unclear whether TRPV1 activation can affect cognitive and synaptic functions in Aβ-induced mouse model of AD. In this study, we investigated the effects of TRPV1 activation on spatial memory and synaptic plasticity in mice treated with Aβ. To induce AD-like pathological and cognitive impairments, adult C57Bl/6 mice were microinjected with Aβ42 (100 μM, 2.5 μl/mouse, i.c.v.). Two weeks after Aβ42 microinjection, spatial learning and memory as well as hippocampal long-term potentiation (LTP) were examined. The results showed that Aβ42 microinjection significantly impaired spatial learning and memory in the Morris water maze and novel object recognition tests compared with controls. These behavioral changes were accompanied by synapse loss and impaired LTP in the CA1 area of hippocampus. More importantly, daily capsaicin (1 mg/kg, i.p.) treatment throughout the experiment dramatically improved spatial learning and memory and synaptic function, as reflected by enhanced hippocampal LTP and reduced synapse loss, whereas the TRPV1 antagonist capsazepine (1 mg/kg, i.p.) treatment had no effects on cognitive and synaptic function in Aβ42-treated mice. These results indicate that TRPV1 activation by capsaicin rescues cognitive deficit in the Aβ42-induced mouse model of AD both structurely and functionally.

Inhibition of AMPAR endocytosis alleviates pentobarbital-induced spatial memory deficits and synaptic depression

Our previous study has shown that pentobarbital causes memory deficits and impairs hippocampal synaptic plasticity. The Tat-GluA2_3Y peptide (GluA2_3Y) prevents activity-dependent α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) endocytosis. It enables early-phase long-term potentiation (LTP) to proceed to late-phase LTP allowing short-term memory to convert to long-term memory. The purpose of this study is to explore the potential effects of GluA2_3Y on pentobarbital-induced memory deficits through behavioral and electrophysiological paradigms. We found that in vivo intrahippocampal infusion of GluA2_3Y (100μM, 1μl per hippocampus) 30min prior to pentobarbital administration (8mM, 1μl per hippocampus) significantly rescued the pentobarbital-induced deficit of memory retrieval in rats during the Morris water maze test. Pre-incubation of GluA2_3Y (10μM) partially rescued bath application of pentobarbital-induced synaptic transmission of the CA3-CA1 pathway in hippocampal slices. More importantly, GluA2_3Y selectively upregulated the synaptic GluA2 expression that was suppressed by pentobarbital. Together, these results suggest that inhibition of GluA2-containing AMPAR endocytosis by GluA2_3Y increases the pentobarbital-suppressed basal synaptic transmission by upregulating the synaptic GluA2, and then subsequently alleviates spatial memory deficits. Therefore, inhibition of AMPAR endocytosis may be a potential therapeutic way to treat memory disorders caused by anesthetics.

Maternal sleep deprivation at different stages of pregnancy impairs the emotional and cognitive functions, and suppresses hippocampal long-term potentiation in the offspring rats

Background

Sleep deprivation during pregnancy is a serious public health problem as it can affect the health of pregnant women and newborns. However, it is not well studied whether sleep deprivation at different stages of pregnancy has similar effects on emotional and cognitive functions of the offspring, and if so, the potential cellular mechanisms also remain poorly understood.

Methods

In the present study, the pregnant rats were subjected to sleep deprivation for 6 h per day by gentle handling during the first (gestational days 1–7), second (gestational days 8–14) and third trimester (gestational days 15–21) of pregnancy, respectively. The emotional and cognitive functions as well as hippocampal long-term potentiation (LTP) were tested in the offspring rats (postnatal days 42-56).

Results

The offspring displayed impaired hippocampal-dependent spatial learning and memory, and increased depressive- and anxiety-like behaviors. Quantification of BrdU-positive cells revealed that adult hippocampal neurogenesis was significantly reduced compared to control. Electrophysiological recording showed that maternal sleep deprivation impaired hippocampal CA1 LTP and reduced basal synaptic transmission, as reflected by a decrease in the frequency and amplitude of miniature excitatory postsynaptic current in the hippocampal CA1 pyramidal neurons.

Conclusions

Taken together, these results suggest that maternal sleep deprivation at different stages of pregnancy disrupts the emotional and cognitive functions of the offspring that might be attributable to the suppression of hippocampal LTP and basal synaptic transmission.