Effects of Oxysophoridine on Rat Hippocampal Neurons Sustained Oxygen–Glucose Deprivation and Reperfusion

Cerebral ischemia caused by a blood supply deficiency triggers various pathophysiological changes. Many factors are involved in the development of ischemia injury. For example the longer ischemia time is more prone to ischemia injury, and the brain is very susceptible to energy-depriving injuries due to its characteristics of low fuel reserves, high aerobic metabolism and low concentrations of oxygen radicals–scavenging enzymes. Rapid reperfusion is the most effective treatment for ischemia, minimizing both structural and functional injuries [1]. Many signaling molecules have been postulated to contribute to ischemia, including both excitotoxicity and oxidative stress [2]. Glutamate emerges as the major excitatory neurotransmitter stimulating energy production in the central nervous system (CNS) that is involved in many neurophysiological functions. A disruption of its homeostasis can damage neurons, which may eventually lead to neural cell death [3]. This neuropathological process, designated excitotoxicity, can induce degeneration of neural cells following an excessive action on its specific ionotropic glutamate receptor, N-methyl-d-aspartate (NMDA) [4]. The activation of NMDA receptor (NMDAR) usually triggers intracellular transduction pathways associated with changes in [Ca]i levels, resulting in neural Ca influx and a cascade of events involving free radical production, and mitochondrial dysfunction can mediate excitotoxicity, resulting in damage to the cell membrane, cytoskeleton, and DNA [5]. Thus, modulating the glutamate pathway is a new concept and therapeutic option to attenuate cerebral ischemia [6]. Oxysophoridine (OSR) is an alkaloid extracted from Siphocampylus verticillatus. Its chemical structure is made of two piperidine rings. The report in the literature has shown that the hydroalcoholic extract of Siphocampylus verticillatus has significant and longlasting antinociception when assessed against both neurogenic and inflammatory models of nociception in mice [7]. Previous work in our laboratory has demonstrated that OSR has an antinociceptive effect and such protection may be mediated by GABA and GABAA receptor up-regulation after OSR pretreatment [8]. In the present study, we tested the hypothesis that the protective effect of OSR was through regulating the glutamate pathway. The hippocampal neurons are cultured using primary rat cells [6]. Sprague-Dawley rats were purchased from the Animal Center of Ningxia medical university, Ningxia, China. All procedures were approved by the Institutional Ethics Committee, and we analyzed the neuroprotective effect of OSR (Ningxia Institute of Materia Medica, Ningxia, China). The purity of OSR was determined to be 99% on the hippocampal neurons sustained oxygen– glucose deprivation/reperfusion (OGD/Rep) in vitro [9]. The cells were randomly divided into six groups: control group; vehicle group (injury by OGD 2 h/Rep 24 h); positive nimodipine control group (12 lM NIM), and different OSR dosage group (5, 20, 80 lM OSR). All the data obtained in the experiments were expressed as mean standard deviation (SD). A one-way analysis of variance (ANOVA) was used to compare the means of six groups. The Student Newman–Keuls’ (SNK)/least significant difference (LSD) test was performed to compare all pair means. All statistical analyses were run with the SPSS 16.0 statistical software package (SPSS, Chicago, IL, USA). P values of <0.05 and 0.01 were considered statistically significant.