Propofol ameliorates electroconvulsive shock-induced learning and memory impairment by regulation of synaptic metaplasticity via autophosphorylation of CaMKIIa at Thr 305 in stressed rats

Alteration of hyperpolarization-activated cation current-mediated metaplasticity contributes to electroconvulsive shock-induced learning and memory impairment in depressed rats

Background

Accompanied by a rapid and effective antidepressant effect, electroconvulsive shock (ECS) can also induce learning and memory impairment. Our previous research reported that metaplasticity is involved in this process. However, the mechanisms still remain unclear. This study investigated the role of I h current in the metaplastic changes and learning and memory impairment induced by ECS in depressive rats.

Methods

Depressive rats received ECS after modelling using chronic unpredictable. ZD7288, a type of I h current inhibitor was used to verify the effect of I h current. The sucrose preference test and Morris water maze were used for behavior testing. Changes in metaplasticity was assessed with the LTD/LTP threshold by stimulation at different frequencies. Spontaneous and evoked action potentials (APs) were measured to confirm difference of neuronal excitability. Additionally, the amplitude of I h current was analyzed.

Results

ECS exerts antidepressant effect, but also induce spatial learning and memory dysfunction. ECS up-regulates the LTD/LTP threshold. In rats treated with ECS, the frequency of spontaneous and evoked APs is significantly reduced. In addition, ECS induces changes in the intrinsic properties of AP, including a decrease of AP-half width and peak amplitude, and an increase in AP time to peak and post-hyperpolarization potential amplitude. In particular, ECS increases both instantaneous and steady-state I h currents. However, Inhibition of I h current with ZD7288 results in a relief of learning and memory impairment and a decrease in threshold, as well as a significant reversal of whole-cell electrophysiological changes.

Conclusion

ECS-induced learning and memory impairment is caused by neuronal hypoexcitability mediated metaplasticity, and upregulation of LTD/LTP threshold by an increase in I h current.

Ciprofol ameliorates ECS-induced learning and memory impairment by modulating aerobic glycolysis in the hippocampus of depressive-like rats

Electroconvulsive shock (ECS) is utilized to treat depression but may cause learning/memory impairments, which may be ameliorated by anesthetics through the modulation of hippocampal synaptic plasticity. Given that synaptic plasticity is governed by aerobic glycolysis, it remains unclear whether anesthetics modulate aerobic glycolysis to enhance learning and memory function. Depression-like behavior in rats was induced by chronic mild unpredictable stress (CUMS), with anhedonia assessed via sucrose preference test (SPT). Depressive-like behaviors and spatial learning/memory were assessed with forced swim test (FST), open field test (OFT), and Morris water maze (MWM) test. Changes in aerobic glycolysis and synaptic plasticity in the hippocampal region of depressive-like rats post-ECS were documented using immunofluorescence analysis, Western blot, Lactate Assay Kit and transmission electron microscopy. Both the OFT and FST indicated that ECS was effective in alleviating depressive-like behaviors. The MWM test demonstrated that anesthetics were capable of attenuating ECS-induced learning and memory deficits. Immunofluorescence analysis, Western blot, Lactate Assay Kit and transmission electron microscopy revealed that the decline in learning and memory abilities in ECS-induced depressive-like rats was correlated with decreased aerobic glycolysis, and that the additional use of ciprofol or propofol ameliorated these alterations. Adding the glycolysis inhibitor 2-DG diminished the ameliorative effects of the anesthetic. No significant difference was observed between ciprofol and propofol in enhancing aerobic glycolysis in astrocytes and synaptic plasticity after ECS. These findings may contribute to understanding the mechanisms by which anesthetic drugs modulate learning and memory impairment after ECS in depressive-like behavior rats.

S-Ketamine Exerts Antidepressant Effects by Regulating Rac1 GTPase Mediated Synaptic Plasticity in the Hippocampus of Stressed Rats

Clinical studies have found that ketamine has a rapid and lasting antidepressant effect, especially in the case of patients with major depressive disorder (MDD). The molecular mechanisms, however, remain unclear. In this study, we observe the effects of S-Ketamine on the expression of Rac1, neuronal morphology, and synaptic transmission function in the hippocampus of stressed rats. Chronic unpredictable mild stress (CUMS) was used to construct stressed rats. The rats were given a different regimen of ketamine (20 mg/kg, i.p.) and Rac1 inhibitor NSC23766 (50 µg, ICV) treatment. The depression-like behavior of rats was evaluated by sucrose preference test and open-field test. The protein expression of Rac1, GluA1, synapsin1, and PSD95 in the hippocampus was detected by Western blot. Pull-down analysis was used to examine the activity of Rac1. Golgi staining and electrophysiological study were used to observe the neuronal morphology and long-term potentiation (LTP). Our results showed that ketamine can up-regulate the expression and activity of Rac1; increase the spine density and the expression of synaptic-related proteins such as GluA1, Synapsin1, and PSD95 in the hippocampus of stressed rats; reduce the CUMS-induced LTP impairments; and consequently improve depression-like behavior. However, Rac1 inhibitor NSC23766 could have effectively reversed ketamine-mediated changes in the hippocampus of rats and counteracted its antidepressant effects. The specific mechanism of S-Ketamine's antidepressant effect may be related to the up-regulation of the expression and activity of Rac1 in the hippocampus of stressed rats, thus enhancing synaptic plasticity.

Effects of N-Methyl-D-aspartate receptor (NMDAR) and Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) on learning and memory impairment in depressed rats with different charge by modified electroconvulsive shock

Background

With the development of modified electroshock therapy (MECT), it has become necessary to increase the electric quantity in order to achieve a good antidepressant effect, but this increase will lead to more serious learning and memory impairment. The purpose of this study was to investigate the intrinsic mechanism of cognitive impairment induced by high-energy electroconvulsive shock (MECS, an animal model of MECT).

Methods

Rats were randomly divided into 6 groups: control (C, n=6), M0, M60, M120, M180, and M240 groups (MECS at 0, 60, 120, 180, and 240 mC stimulation intensity after 80 mg/kg propofol, with 12 rats in each group). Their depression-like behavior and learning and memory ability were evaluated by sucrose preference test (SPT), open field test (OFT), and Morris water maze test (MWM). The expression of phospho-NMDA receptor 1 (GluN1), GluN2A, GluN2B, Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα), p-T305-CaMKII, and postsynaptic densities-95 (PSD-95) in hippocampus were detected by western blot. The co-expression of CaMKIIα and GluN2B subunit was detected by co-immunoprecipitation (CO-IP).

Results

The chronic unpredictable mild stresses (CUMS) procedure successfully induced depression-like behavior in rats, which was improved in varying degrees after MECS. The results showed that the expression of GluN1, GluN2A, GluN2B, and PSD-95 decreased with the increase of charge, while p-T305-CaMKII increased, which led to the deterioration of learning and memory ability, but the expression change of CaMKIIα was not statistically significant.

Conclusions

Increase in the MECS charge adjusts the synaptic plasticity by changing the binding amount of CaMKIIα and its subunit GluN2B and the level of CaMKII autophosphorylation, thereby impairing learning and memory functions.

Inhibition of CB1 receptor alleviates electroconvulsive shock-induced memory impairment by regulating hippocampal synaptic plasticity in depressive rats

Electroconvulsive therapy (ECT) is one of the most effective treatments for depression, but it can cause cognitive deficit. Unfortunately, effective preventive measures are still lacking. The endocannabinoid system is thought to play a key role in regulation of cognitive process. Whether the endocannabinoid system is involved in the learning and memory impairment caused by ECS remain unclear. In this work, we first found that cannabinoid receptor type 1 (CB1R) and 2-arachidonoylglycerol (2-AG) were strongly expressed in hippocampus by electroconvulsive shock (ECS) in a rat depression model established by chronic mild stress (CMS). Pharmacological inhibition of CB1R using AM251 in vivo resulted in a pronounced relief in ECS-induced spatial learning and memory impairment as well as in a marked reversal of impaired hippocampal long-term potentiation (LTP), and reduced synapse-related proteins expression. Furthermore, results of sucrose preference test (SPT) and open-field test (OFT) showed that AM251 had no significant impact on the therapeutic effects of ECS on pleasure and psychomotor activity. Taken together, we identified that CB1R is involved in the ECS-induced spatial learning and memory impairment and Inhibition of CB1R facilitates the recovery of memory impairment and hippocampal synaptic plasticity, without interfering with the therapeutic effects of ECS in depressed rats.

Reduced Synaptic Plasticity Contributes to Resistance Against Constant-Stimulus Electroconvulsive Treatment in a Rat Model of Stress-Induced Depression

PURPOSE

Depression is a common mood disorder in humans worldwide. Electroconvulsive therapy (ECT) remains the most effective treatment for patients with drug-resistant or severe depression; however, during ECT, electrical resistance can occur, antagonizing ECT efficacy. We aimed to investigate how depressed patients develop resistance to electric shocks during ECT.

METHODS

Rats exposed to chronic unpredictable stress exert similar impairments in hippocampal synaptic plasticity as those in depressed humans, including hippocampal neuronal atrophy and reduced synaptic function and synapse-related proteins. Therefore, a rat model was used to model depressive-like behaviors in the current study. Depression-like behavior was stimulated in Sprague Dawley (SD) rats that were then randomized into six groups: control group (C); a rat model of stress-induced depression group (D); and four groups in which a rat model of stress-induced depression received one, three, five, or seven electroconvulsive shocks (ECS; DE1, DE3, DE5, and DE7). The sucrose preference test (SPT) and Morris water maze (MWM) were utilized to evaluate anhedonia and spatial learning and memory in rats, respectively. Synaptic plasticity was recorded electrophysiologically in terms of field excitatory postsynaptic potential (fEPSP) and long-term potentiation (LTP).

RESULTS

The rat model of stress-induced depression triggered a decrease in the sucrose preference percentage (SPP) and the baseline fEPSP slope relative to those observed for the C group, and these changes were significantly rescued by ECT in a shock number-dependent manner within five shocks. However, the rat model of stress-induced depression displayed an increase in the escape latency and a decrease in space exploration time, in addition to decreased LTP relative to those in the C group, which was further augmented by ECT in a shock number-dependent manner within five shocks.

CONCLUSION

Changes in synaptic plasticity might be responsible for the development of resistance against constant-stimulus ECT in a rat model of stress-induced depression.

Effects of electroconvulsive shock on neuro-immune responses: Does neuro-damage occur?

Electroconvulsive therapy (ECT) is one of the most effective treatments for treatment-resistant depression. However, this treatment may produce memory impairment. The mechanisms of the cognitive adverse effects are not known. Neuroimmune response is related to the cognitive deficits. By reviewing the available animal literature, we examined the glia activation, inflammatory cytokines, neuron oxidative stress responses, and neural morphological changes following electroconvulsive shock (ECS) treatment. The studies showed that ECS activates microglia, upregulates neuro-inflammatory cytokines, and increases oxidative stress responses. But these effects are rapid and may be transient. They normalize as ECS treatment continues, suggesting endogenous neuroprotection may be mobilized. The transient changes are well in line with the clinical observations that ECT usually does not cause significant long-lasting retrograde amnesia. The longitudinal studies will be particularly important to explore the dynamic changes of neuroplasticity following ECT (Jonckheere et al., 2018). Investigating the neuroplasticity changes in animals that suffered chronic stress may also be crucial to giving support to the translation of preclinical research.

Effect of different charges of modified electroconvulsive seizure on the cognitive behavior in stressed rats: Effects of GluR1 phosphorylation and CaMKIIα activity

Electroconvulsive therapy (ECT) is an efficient therapy for major depression and modern ECT requires anesthesia to enhance safety. However, the commonly used anesthetic, propofol, may weaken the treatment efficacy. A recent study confirmed that ketamine rapidly reduced the symptoms of depression in affected patients. A previous study found that electroconvulsive seizure (ECS), the animal model for ECT, under anesthesia of low-dose ketamine combined with propofol could enhance the antidepressant efficacy and improve the cognitive performance. The present study aimed to investigate the responses to different charges (0, 60, 120, 180 or 240 mC) of ECS under compound anesthetics, ketamine combined with propofol, in stressed rats and the underlying mechanisms to aid in optimization of treatment regimens. The results indicated that ECS exhibited an improved antidepressant effects at 120 mC compared with 60 mC, however, no significant differences in antidepressant effects were identified among the 120, 180 and 240 mC groups. Furthermore, rats subjected to ECS at 120 mC exhibited the best cognitive performance. The phosphorylation levels of calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) at Thr286, glutamate receptor 1 (GluR1) at Ser831 and cAMP-response element-binding protein (CREB) at the Ser133 were higher in the 120-mC group compared with all other groups. These results indicated that the ECS at medium intensity (120 mC) with administration of compound anesthetics may exert an improved therapeutic effect on depression compared with other intensities (0, 60, 180 and 240 mC). The results also suggested that the improvement in cognitive function in stressed rats may be attributed to the phosphorylation of CaMKIIα (Thr286), GluR1 (Ser831) and CREB (Ser133).

Changes in synaptic plasticity are associated with electroconvulsive shock-induced learning and memory impairment in rats with depression-like behavior

BACKGROUND

Accompanied with the effective antidepressant effect, electroconvulsive shock (ECS) can induce cognitive impairment, but the mechanism is unclear. Synaptic plasticity is the fundamental mechanism of learning and memory. This study aimed to investigate the effect of ECS on synaptic plasticity changes in rats with depression-like behavior.

METHODS

Chronic unpredictable mild stress procedure was conducted to establish a model of depression-like behavior. Rats were randomly divided into the following three groups: control group with healthy rats (group C), rats with depression-like behavior (group D), and rats with depression-like behavior undergoing ECS (group DE). Depression-like behavior and spatial learning and memory function were assessed by sucrose preference test and Morris water test, respectively. Synaptic plasticity changes in long-term potentiation (LTP), long-term depression (LTD), depotentiation, and post-tetanic potentiation (PTP) were tested by electrophysiological experiment.

RESULTS

ECS could exert antidepressant effect and also induced spatial learning and memory impairment in rats with depression-like behavior. And, data on electrophysiological experiment showed that ECS induced lower magnitude of LTP, higher magnitude of LTD, higher magnitude of depotentiation, and lower magnitude of PTP.

CONCLUSION

ECS-induced learning and memory impairment may be attributed to postsynaptic mechanism of LTP impairment, LTD and depotentiation enhancement, and presynaptic mechanism of PTP impairment.

Anesthetics alleviate learning and memory impairment induced by electroconvulsive shock by regulation of NMDA receptor-mediated metaplasticity in depressive rats

Along with its outstanding antidepressant effect, electroconvulsive shock (ECS) can induce learning and memory impairment. Propofol and ketamine have shown to be useful in alleviating the learning and memory impairment. Nevertheless, the mechanism still remains unclear. This study investigated the role of NMDA receptor (NMDAR)-mediated metaplasticity in the learning and memory impairment induced by ECS, as well as the neuroprotective effect of propofol and ketamine in depressive rats. Rats received ECS or ECS under anesthetics after chronic unpredictable mild stress procedure. Long-term potentiation (LTP) was tested by extracellular recording. LTD/LTP threshold was assessed by stimulation of different frequencies. Additionally, NMDAR-mediated field excitatory postsynaptic potential (fEPSP) and NMDAR input/output relationship were detected under hippocampal slice perfusion. Results showed that propofol or low-dose ketamine could partially alleviate ECS-induced LTP impairment, while propofol combined with low-dose ketamine almost reversed the LTP impairment. LTP under ECS was increased by stronger stimulation. ECS could up-regulated LTD/LTP threshold, while propofol or ketamine could down-regulate it. Moreover, ECS activated NMDAR, while propofol and ketamine could inhibit the activation of NMDAR. NMDAR input/output relationship decrease was induced by preconditioning (an analog of ECS in hippocampal slice), however, NMDAR input/output relationship increased by propofol or ketamine. In conclusion, ECS-induced cognitive impairment is caused by NMDAR-mediated metaplasticity via up-regulation of LTD/LTP threshold. Propofol or ketamine alleviates the cognitive impairment, possibly by down-regulating the threshold via inhibition of NMDAR activation induced by ECS.