Comparison of the neuropsychological mechanisms of 2,6-diisopropylphenol and N-methyl-D-aspartate receptor antagonist against electroconvulsive therapy-induced learning and memory impairment in depressed rats

Shared effects of electroconvulsive shocks and ketamine on neuroplasticity: A systematic review of animal models of depression

Electroconvulsive shocks (ECS) and ketamine are antidepressant treatments with a relatively fast onset of therapeutic effects compared to conventional medication and psychotherapy. While the exact neurobiological mechanisms underlying the antidepressant response of ECS and ketamine are unknown, both interventions are associated with neuroplasticity. Restoration of neuroplasticity may be a shared mechanism underlying the antidepressant efficacy of these interventions. In this systematic review, literature of animal models of depression is summarized to examine the possible role of neuroplasticity in ECS and ketamine on a molecular, neuronal, synaptic and functional level, and specifically to what extent these mechanisms are shared between both interventions. The results highlight that hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) levels are consistently increased after ECS and ketamine. Moreover, both interventions positively affect glutamatergic neurotransmission, astrocyte and neuronal morphology, synaptic density, vasculature and functional plasticity. However, a small number of studies investigated these processes after ECS. Understanding the shared fundamental mechanisms of fast-acting antidepressants can contribute to the development of novel therapeutic approaches for patients with severe depression.

The effect of erythropoietin on electroconvulsive stimulation induced cognitive impairment in rats

Electroconvulsive therapy (ECT) is the most effective and fast-acting treatment for severe depression but associated with troublesome cognitive side-effects. Systemically administered erythropoietin (EPO) crosses the blood-brain-barrier and is a promising treatment for cognitive dysfunction in a wide array of neuropsychiatric and neurological disorders. In this study we trained rats to locate a submerged platform in a water maze and then subjected them to electroconvulsive stimulations (ECS, the rodent equivalent to ECT) and EPO treatment. We then analysed their ability to remember and relearn the location of the platform. In addition, we examined "wall-clinging" (thigmotaxis), a behavioural indicator of stress. ECS caused significant deficit in a probe trial administered after three weeks (nine stimulations) as well as one week (six stimulations) of treatment, indicative of induction of retrograde amnesia. ECS had no effect on relearning of the water maze task or performance in a subsequent probe trial. EPO treatment did not ameliorate the ECS-induced retrograde amnesia, but after nine ECS stimulations the animals that had received EPO relearned the position of the hidden platform faster than the animals that had not. We also found EPO to decrease "wall-clinging" behaviour, suggesting an effect of EPO on the stress response in rats. Thus, we establish the Morris Water Maze as a suitable model for ECS-induced memory loss in rats and provide some evidence for potential beneficial effects of EPO.

Lychee seed extract protects against neuronal injury and improves cognitive function in rats with type II diabetes mellitus with cognitive impairment

Lychee seed is a traditional Chinese medicine and has many beneficial effects such as modulation of blood sugar and lipids, antioxidation, antivirus and antitumor. Studies have indicated that type II diabetes mellitus (T2DM) and Alzheimer's disease (AD) share common biological mechanisms including insulin resistance, impaired glucose metabolism, β-amyloid (Aβ) formation, oxidative stress and presence of advanced glycation end products (AGEs). The present study investigated the effects of lychee seed extract (LSE) on neuroprotection, cognitive function improvement and possible underlying mechanisms in a rat model of T2DM with cognitive impairment. We analyzed the chemical profile of LSE using a UHPLC-SPD chromatogram and evaluated its effect on the improvement of spatial learning and memory of rats by a Morris water maze. The levels of glucose, insulin, Aβ, AGEs, Tau protein and acetylcholinesterase in the blood and/or hippocampus of rats were determined by blood-glucose meter, radioimmunoassay, chemical chromatometry, enzyme-linked immunosorbent assay (ELISA) and immunohistochemical analysis, respectively. Results demonstrated that LSE consists of eight major and around 20 minor ingredients, and it remarkably prevents neuronal injury and improves cognitive functions in T2DM rats. The levels of glucose, insulin, Aβ, AGEs and Tau protein were significantly increased in the blood and/or hippocampus of T2DM rats, while LSE remarkably decreased their levels compared to vehicle treatment (P<0.01). The possible mechanisms may be associated with IR improvement and decreased formations of Aβ, AGEs and Tau protein in the hippocampus of T2DM rats. LSE may be developed as the agent for the treatment of T2DM and/or AD clinically.

Biflorin Ameliorates Memory Impairments Induced by Cholinergic Blockade in Mice

To examine the effect of biflorin, a component of Syzygium aromaticum, on memory deficit, we introduced a scopolamine-induced cognitive deficit mouse model. A single administration of biflorin increased latency time in the passive avoidance task, ameliorated alternation behavior in the Y-maze, and increased exploration time in the Morris water maze task, indicating the improvement of cognitive behaviors against cholinergic dysfunction. The biflorin-induced reverse of latency in the scopolamine-treated group was attenuated by MK-801, an NMDA receptor antagonist. Biflorin also enhanced cognitive function in a naïve mouse model. To understand the mechanism of biflorin for memory amelioration, we performed Western blot. Biflorin increased the activation of protein kinase C-ζ and its downstream signaling molecules in the hippocampus. These results suggest that biflorin ameliorates drug-induced memory impairment by modulation of protein kinase C-ζ signaling in mice, implying that biflorin could function as a possible therapeutic agent for the treatment of cognitive problems.