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Radiation-induced brain injury is a serious complication after cranio-cerebral radiotherapy, which affects the patient's quality of life and survival. A large number of studies have shown that various mechanisms such as neuronal apoptosis, blood-brain barrier damage, and synaptic dysfunction may be related to radiation-induced brain injury. Acupuncture has an important role in clinical rehabilitation of various brain injuries. As a new type of acupuncture, electroacupuncture has the characteristics of strong control ability, uniform and long-lasting stimulation, and is widely used in clinic. This article reviews the effects and mechanisms of electroacupuncture on radiation-induced brain injury, in order to provide a theoretical basis and experimental support for reasonable clinical application.

The aim of the present study was to investigate the effects of different courses of electroacupuncture on synaptic structure and synaptic function-related proteins expression in the hippocampal CA1 region of radiation-induced brain injury mice. Sixty C57BL/6J male mice were randomly divided into control group, radiation-induced brain injury model group, 1-week electroacupuncture group (EA1), 2-week electroacupuncture group (EA2), 3-week electroacupuncture group (EA3), and electroacupuncture-control (EA-Ctrl) group. The mice in model group were exposed to X-ray irradiation (8 Gy, 10 min) to establish radiation-induced brain injury model. The mice in EA groups were acupunctured at electroacupuncture points (Baihui, Fengfu and bilateral Shenshu) for 1 week, 2 weeks and 3 weeks respectively after radiation. Immunohistochemistry was used to observe synaptic structure in hippocampal CA1 region. The expressions of brain-derived neurotrophic factor (BDNF), synapsin-1 and postsynaptic density 95 (PSD95) in the hippocampal CA1 region of each group were detected by RT-PCR and Western blotting. The results showed that the nuclear gap in model and EA-Ctrl groups was significantly decreased compared to control group, however nucleus to cytoplasm ratio was significantly increased. The synaptic cleft, postsynaptic density (PSD) thickness, the mitochondrial surface density, volume density and specific surface area were significantly reduced. Compared with model group, the nucleus to cytoplasm ratio of EA2 group was significantly decreased, the PSD thickness and mitochondrial volume density were significantly increased; the nuclear gap of EA3 group was significantly increased, nucleus to cytoplasm ratio was significantly decreased, synaptic cleft and PSD thickness were significantly increased, and the mitochondrial surface density and specific surface area were all increased significantly. In addition, compared with the control group, the gene and protein expressions of BDNF, synapsin-1 and PSD95 in the hippocampal CA1 region of the model group and EA-Ctrl group were significantly decreased. However, compared with the model group, the gene expression of synapsin-1 in EA groups was significantly up-regulated, the gene expression of BDNF in EA1 and EA2 groups was significantly up-regulated, and the gene expression of PSD95 in EA2 group was significantly up-regulated. Moreover, the protein expressions of BDNF, synapsin-1 and PSD95 of EA groups were significantly up-regulated compared with the model group. These results indicate that the synaptic structure and the expression of synaptic function-related proteins in hippocampal CA1 region were injured by radiation exposure, whereas electroacupuncture intervention can significantly improve the synaptic structure and function damage caused by radiation.

Calcitonin gene-related peptide (CGRP) is a neuropeptide coded by the calcitonin gene and divided into α and β subtypes. CGRP is widely distributed throughout the human body and highly expressed in the peripheral and central nervous system. Studies have shown that CGRP plays a role in a variety of physiological and pathophysiological activities, such as the formation and transmission of nociceptive signal, as well as the regulation of cardiovascular function. Recently, more and more researches have shown that CGRP is involved in the regulation of synaptic plasticity, cognitive function and learning memory in the central nervous system. This paper reviews the role of CGRP in regulation of synaptic plasticity and process of emotional memory, hoping to provide a new molecular target and theoretical basis for clinical treatment of neurological diseases.

The purpose of this study was to explore the effects of calcitonin gene-related peptide (CGRP) on the long-term depression (LTD) of hippocampus in mice. Sixty C57BL/6J mice (30 days old) were randomly divided into control group, three CGRP (50, 100, and 200 nmol/L) groups, CGRP + CGRP 8-37 group and CGRP + APV group (10 mice for each group). The effects of exogenous application of different concentrations of CGRP on synaptic plasticity and LTD in hippocampus of mice were detected by in vitro recording of local field potential. The results showed that higher doses (100 and 200 nmol/L) of CGRP significantly enhanced the induction of LTD in the hippocampus. Moreover, CGRP increased the magnitude of N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents. The above-mentioned effects of CGRP were blocked by either CGRP selective antagonist CGRP 8-37 or NMDA receptor antagonist APV. These results suggest that CGRP can dose-dependently enhance the induction of LTD in hippocampus of mice, and the underlying mechanism involves the mediation of NMDA receptor function.

The present study was aimed to investigate the effects and mechanisms of electro-acupuncture (EA) on proliferation and differentiation of neural stem cells in the hippocampus of C57 mice exposed to different doses of X-ray radiation. Thirty-day-old C57BL/6J mice were randomly divided into control, irradiation, and EA groups. The control group was not treated with irradiation. The irradiation groups were exposed to different doses of X-ray (4, 8 or 16 Gy) for 10 min. The EA groups were electro-acupunctured at Baihui, Fengfu and bilateral Shenyu for 3 courses of treatment after X-ray radiation. Immunohistochemistry was used to evaluate proliferation and differentiation of the hippocampal neural stem cell. RT-PCR and Western blot were used to detect mRNA and protein expressions of Notch1 and Mash1 in the hippocampus, respectively. The results showed that, compared with the control group, the numbers of BrdU positive cells (4, 8 Gy subgroup) and BrdU/NeuN double-labeling positive cells (3 dose subgroups) were decreased significantly in the irradiation group, but the above changes could be reversed by EA. Compared with the control group, the number of BrdU/GFAP double-labeling positive cells in each dose subgroup of irradiation group was decreased significantly, while EA could reverse the change of 4 and 8 Gy dose subgroups. In addition, compared with the control group, the expression levels of Notch1 mRNA and protein in hippocampus were up-regulated, and the expression levels of Mash1 mRNA and protein were significantly decreased in each dose subgroup of irradiation group. Compared with irradiation group, the expression levels of Notch1 mRNA and protein in hippocampus of EA group were decreased significantly in each dose subgroup, and the expression levels of Mash1 mRNA and protein were increased significantly in 4 and 8 Gy subgroups. These results suggest that irradiation affects the proliferation and differentiation of neural stem cells in hippocampus of mice, whereas EA may significantly increase the proliferation and differentiation of hippocampal neural stem cells via the regulation of Notch signaling pathway.

The purpose of this study was to explore the effects of different concentrations of calcitonin gene-related peptide (CGRP) on long-term potentiation (LTP) in the hippocampus of mice. C57BL/6J mice (30 days old) were randomly divided into control group, three CGRP groups, and CGRP + CGRP 8-37 group (10 mice for each group). Different concentrations of CGRP (50, 100 and 200 nmol/L) were given to the hippocampal slices of mice. The presynaptic release of neurotransmitters and the induction of LTP were measured by extracellular field recording techniques. The result showed that different concentrations of CGRP did not affect the presynaptic release of neurotransmitters, but 100 and 200 nmol/L CGRP increased the amplitude of LTP induced in the hippocampus of mice. This facilitation effect of CGRP was blocked by its specific antagonist CGRP 8-37 . These results suggest that CGRP dose-dependently facilitates the induction of LTP in the hippocampus of mice through its specific receptor.

Aquaporin-4 (AQP-4) is the predominant water channel in the central nervous system (CNS) and primarily expressed in astrocytes. Astrocytes have been generally believed to play important roles in regulating synaptic plasticity and information processing. However, the role of AQP-4 in regulating synaptic plasticity, learning and memory, cognitive function is only beginning to be investigated. It is well known that synaptic plasticity is the prime candidate for mediating of learning and memory. Long term potentiation (LTP) and long term depression (LTD) are two forms of synaptic plasticity, and they share some but not all the properties and mechanisms. Hippocampus is a part of limbic system that is particularly important in regulation of learning and memory. This article is to review some research progresses of the function of AQP-4 in synaptic plasticity, learning and memory, and propose the possible role of AQP-4 as a new target in the treatment of cognitive dysfunction.

The aim of the present study was to explore the effects of different doses of calcitonin gene-related peptide (CGRP) injected into the central nucleus of amygdala on cognitive function, learning and memory of mice. C57BL/6J mice (30 days old) were randomly divided into control, sham, and three CGRP groups (10 mice for each group). Three doses of CGRP (200, 400 and 800 ng) were bilaterally administered into the central nucleus of the amygdala. Open field test was used to assess cognitive function. Novel object recognition and Morris water maze test were used to evaluate learning and memory of the mice. The results of open field test showed that 800 ng CGRP significantly increased the locomotive score. The results of novel objective recognition test showed that 400 ng CGRP significantly increased the recognition index. Compared with control group, 400 and 800 ng CGRP groups showed significantly shortened latency period and increased crossing times. Simultaneously, the latency periods of 400 and 800 ng CGRP groups were shorter than that of 200 ng CGRP group. These results suggest that bilateral injection of CGRP into amygdala dose-dependently enhances the learning and memory function of mice.

The spatial distribution of the hippocampus-cerebellar projection and the connection between the projection area of hippocampus in the cerebellum and cerebellar nuclei were studied by means of electrophysiological and HRP labelling techniques. Polysynaptic responses of Purkinje cell's simple and complex spike in the lobule VI could be evoked by stimulation of the area CA1/CA3 of the dorsal hippocampus. These results suggest that there are polysynaptic projections from CA1 and CA3 areas of dorsal hippocampus to the lobule VI of cerebellar cortex, and the last relay fibers for these projections are mossy fiber and/or climbing fiber. It is also shown that this hippocampus-cerebellar projection predominantly terminates at the lobule VI of cerebellar cortex, 0.8-1.4 mm lateral to the midline. The projection from CA1 area is mainly contralateral, whereas the projection from CA3 area is mainly ipsilateral. The results with HRP labelling indicate that the projection area of hippocampus is an interpositus zone of the lobule VI. Reciprocal connections may exist between this cortical area and the interpositus nucleus.