Cannabidiol promotes neurogenesis in the dentate gyrus during an abstinence period in rats following chronic exposure to methamphetamine

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Abstract
Chronic methamphetamine (meth) abuse can lead to certain deficits in the hippocampal function by affecting the hippocampal neurogenesis and plasticity. To determine whether cannabidiol (CBD) can promote proliferation and maturation of neuronal progenitor cells, this study investigated the CBD effect on neurogenesis in the hippocampal dentate gyrus (DG) following chronic exposure to meth in rats. The rats received 2 mg/kg of meth twice a day for ten days. Next, immunofluorescence was performed to evaluate the effect of intracerebroventricular (ICV) administration of CBD (50 μg/5 μL) over an abstinence period (ten days) on the expression levels of neurogenesis markers, such as Ki67, NeuN, and doublecortin (DCX). Moreover, neuronal degeneration in the hippocampus was assessed using Nissl staining. According to our findings, repeated ICV administration of CBD improved cell proliferation and neurogenesis and increased the number of Ki-67 and DCX-positive cells in the abstinence period. Meanwhile, meth treatment subjects caused a significant decrease in the number of neurogenesis makers, as compared to the control group. The neurogenesis markers (Ki-67 and DCX) could be somewhat reversed, while NeuN did not show any significant increase in the CBD group. Our findings demonstrated that CBD can induce neuroprotective effects by modulating neurogenesis. Therefore, it can provide a promising therapeutic approach to improve cognitive performance following chronic exposure to psychostimulant drugs, including meth.