Abstract
Background: In light of therapeutic limitations in Alzheimer's disease (AD), recent alternative or add-on treatment approaches such as non-invasive brain stimulation through transcranial electrical stimulation (tES) have gained attention. Translational studies have postulated that transcranial direct current stimulation (tDCS) is potentially a novel therapeutic option to reverse or stablize cognitive impairments. The aim of this study was to comparatively evaluate the effects of the four main paradigms of tES, including tDCS, transcranial alternative current stimulation (tACS), transcranial random noise stimulation (tRNS), and transcranial pulse current stimulation (tPCS) on beta amyloid 25-35 (Aβ 25-35)-induced memory impairment in male rats submitted to the Morris water maze (MWM) task. Method: To develop AD model in Sprague-Dawley male rats weighing 250-270, the cannula was implanted bilaterally into the hippocampi. Aβ 25-35 (5 μg/2.5 ml/ day) was microinjected bilaterally for 4 days. Then, tES was applied to the animals for 6 days. Subsequently, rats’ learning and memory function was evaluated on day 11-14 in MWM task. Results: Our findings indicated that tDCS, tACS, tRNS reduced escape latency, while such an effect was not observed in tPCS paradigm. In terms of the duration of animals’ presence in the platform quadrant, tDCS and tACS increased the outcome measure. Conclusion: We conclude that tDCS and tACS are more effective than the other two examined paradigms of tES in ameliorating learning and memory impairments.
Highlights
Alzheimer's disease (AD) is a progressive disorder characterized by the loss of neurons and synapses, especially in the hippocampus, which eventually leads to forgetfulness
Our findings revealed that different paradigms of transcranial electrical stimulation (tES) prevented Aβ-induced memory deficit in Morris water maze (MWM) task
In a study conducted in 2014, it was shown that injection of Aβ 25-35 into the hippocampus caused memory impairment in MWM task [30], which was in agreement to our findings
Summary
Alzheimer's disease (AD) is a progressive disorder characterized by the loss of neurons and synapses, especially in the hippocampus, which eventually leads to forgetfulness. The stimulation is done by applying direct current (DC) over the scalp using electrodes which are encapsulated by sponge embedded in saline or rubber electrodes with guiding gels [5]. This technique can induce long-term and polarityspecific changes in the excitability of the motor cortex in humans [6]. The aim of this study was to comparatively evaluate the effects of the four main paradigms of tES, including tDCS, transcranial alternative current stimulation (tACS), transcranial random noise stimulation (tRNS), and transcranial pulse current stimulation (tPCS) on beta amyloid 25-35 (Aβ 25-35)-induced memory impairment in male rats submitted to the Morris water maze (MWM) task. In terms of the duration of animals’ presence in the platform quadrant, tDCS and tACS increased the outcome measure
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