Xing-Jie Ping

Morphine-induced conditioned place preference in rats is inhibited by electroacupuncture at 2 Hz: Role of enkephalin in the nucleus accumbens

Our previous studies have demonstrated that morphine-induced conditioned place preference (CPP) can be inhibited by 2 Hz electroacupuncture (EA). This inhibition can be blocked by either the opioid receptor antagonist naloxone (i.p.) or lesion in the nucleus accumbens (NAc), providing evidence that endogenous opioid system in the NAc mediates the effects of EA. Here we report that 1) A single session of 2 Hz EA produced a significant increase of the content of enkephalin in the NAc of morphine-induced CPP rats, and this effect was stronger in three consecutive sessions of EA; 2) Intracerebroventricular injection of the mu-opioid receptor antagonist CTAP or delta-opioid receptor antagonist NTI, but not kappa-opioid receptor antagonist nor-BNI, dose-dependently reversed the inhibitory effects of 2 Hz EA on the expression of morphine-induced CPP; 3) Three consecutive sessions of 2 Hz EA up-regulated the mRNA level of preproenkephalin in the NAc of morphine-induced CPP rats. The results suggest that the inhibitory effects of 2 Hz EA on the expression of the morphine CPP is mediated by mu- and delta-, but not kappa-opioid receptor, possibly via accelerating both the release and synthesis of enkephalin in the NAc. These findings support the possibility of using 2 Hz EA for the treatment of opiate addiction.

Electroacupuncture frequency-related transcriptional response in rat arcuate nucleus revealed region-distinctive changes in response to low- and high-frequency electroacupuncture.

Electroacupuncture (EA) has been clinically applied for treating different medical conditions, such as pain, strain, and immune diseases. Low‐ and high‐frequency EAs have distinct therapeutic effects in clinical practice and experimental studies. However, the molecular mechanism of this difference remains obscure. The arcuate nucleus (Arc) is a critical region of the hypothalamus and is responsible for the effect of EA stimulation to remote acupoints. Gene expression profiling provides a powerful tool with which to explore the basis of physiopathological responses to external stimulus. In this study, using cDNA microarray, we investigated gene expressions in the rat Arc region induced by low‐frequency (2‐Hz) and high‐frequency (100‐Hz) EAs to two remote acupoints, zusanli (ST36) and sanyinjiao (SP6). We have found that more genes were differentially regulated by 2‐Hz EA than 100‐Hz EA (154 vs. 66 regulated genes/ESTs) in Arc, especially those related to neurogenesis, which was confirmed by qRT‐PCR. These results demonstrate that the expression level of genes in the Arc region could be effectively regulated by low‐frequency EA, compared with high‐frequency EA, helping to uncover the mechanisms of the therapeutic effects of the low‐frequency EA. Our results also indicate different‐frequency EAs are spatially specific.

Multiple 100 Hz electroacupuncture treatments produced cumulative effect on the suppression of morphine withdrawal syndrome: Central preprodynorphin mRNA and p-CREB implicated.

Alleviating opiate withdrawal syndrome in addicts is a critical precondition to break away from drug and further to prevent reuse. Electroacupuncture (EA) was claimed to be effective for alleviating withdrawal syndrome, but the optimal protocol remained unclear. In the present study we found that (1) 100 Hz EA administered 12-24h after the last morphine injection suppressed the withdrawal syndrome in rats, multiple sessions of EA were more effective than single session, with the after-effect lasting for at least 7 days. (2) A down-regulation of preprodynorphin (PPD) mRNA level was observed in spinal cord, PAG and hypothalamus 60 h after the last morphine injection, which could be reversed by multiple sessions, but not a single session of EA. (3) Accompanied with the decrease of PPD mRNA level, there was an up-regulation of p-CREB in the three CNS regions, which was abolished by 100 Hz EA treatment. The findings suggest that down-regulation of p-CREB and acceleration of dynorphin synthesis in spinal cord, PAG and hypothalamus may be implicated in the cumulative effect of multiple 100Hz EA treatment for opioid detoxification.

The possible involvement of endogenous ligands for mu-, delta-and kappa-opioid receptors in modulating morphine-induced CPP expression in rats

Previous studies suggested that electroacupuncture (EA) can suppress opioid dependence by the release of endogenous opioid peptides. To explore the site of action and the receptors involved, we tried to inject highly specific agonists for mu-, delta- and kappa-opioid receptors into the CNS to test whether it can suppress morphine-induced conditioned place preference (CPP) in the rat. Male Sprague-Dawley rats were trained with 4 mg/kg morphine, i.p. for 4 days to establish the CPP model. This CPP can be prevented by (a) i.p. injection of 3 mg/kg dose of morphine, (b) intracerebroventricular (i.c.v.) injection of micrograms doses of the selective mu-opioid receptor agonist DAMGO, delta-agonist DPDPE or kappa-agonist U-50,488H or (c) microinjection of DAMGO, DPDPE or U50488H into the shell of the nucleus accumbens (NAc). The results suggest that the release of endogenous mu-, delta- and kappa-opioid agonists in the NAc shell may play a role for EA suppression of opiate addiction.

Transcriptome profiling analysis reveals region-distinctive changes of gene expression in the CNS in response to different moderate restraint stress

J. Neurochem. (2010) 113, 1436–1446.

Differences in neural-immune gene expression response in rat spinal dorsal horn correlates with variations in electroacupuncture analgesia.

Background Electroacupuncture (EA) has been widely used to alleviate diverse pains. Accumulated clinical experiences and experimental observations indicated that significant differences exist in sensitivity to EA analgesia for individuals of patients and model animals. However, the molecular mechanism accounting for this difference remains obscure. Methodology/Principal Findings We classified model male rats into high-responder (HR; TFL changes >150) and non-responder (NR; TFL changes ≤0) groups based on changes of their pain threshold detected by tail-flick latency (TFL) before and after 2 Hz or 100 Hz EA treatment. Gene expression analysis of spinal dorsal horn (DH) revealed divergent expression in HR and NR after 2 Hz/100 Hz EA. The expression of the neurotransmitter system related genes was significantly highly regulated in the HR animals while the proinflammation cytokines related genes were up-regulated more significantly in NR than that in HR after 2 Hz and 100 Hz EA stimulation, especially in the case of 2 Hz stimulation. Conclusions/Significance Our results suggested that differential regulation and coordination of neural-immune related genes might play an important role for individual variations in analgesic effects responding to EA in DH. It also provided new candidate genes related to EA responsiveness for future investigation.

Genomewide Analysis of Rat Periaqueductal Gray-Dorsal Horn Reveals Time-, Region- and Frequency-Specific mRNA Expression Changes in Response to Electroacupuncture Stimulation

Electroacupuncture (EA) has been widely applied for illness prevention, treatment or rehabilitation in the clinic, especially for pain management. However, the molecular events that induce these changes remain largely uncharacterized. The periaqueductal gray (PAG) and the spinal dorsal horn (DH) have been verified as two critical regions in the response to EA stimulation in EA analgesia. In this study, a genetic screen was conducted to delineate the gene expression profile in the PAG-DH regions of rats to explore the molecular events of the analgesic effect induced by low-frequency (2-Hz) and high-frequency (100-Hz) EAs. Microarray analysis at two different time points after EA stimulation revealed time-, region- and frequency-specific gene expression changes. These expression differences suggested that modulation of neural-immune interaction in the central nervous system played an important role during EA analgesia. Furthermore, low-frequency EA could regulate gene expression to a greater degree than high-frequency EA. Altogether, the present study offers, for the first time, a characterized transcriptional response pattern in the PAG-DH regions followed by EA stimulation and, thus, provides a solid experimental framework for future in-depth analysis of the mechanisms underlying EA-induced effects.

Transcutaneous Electrical Acupoint Stimulation for the Treatment of Withdrawal Syndrome in Heroin Addicts

OBJECTIVE To assess the therapeutic effect of transcutaneous electric acupoint stimulation (TEAS) for the treatment of withdrawal syndrome in heroin addicts. METHODS A total of 63 male heroin addicts with withdrawal score higher than 20 were recruited in the Detoxification Center of Zhongshan city, Guangdong province, China. They were randomly distributed into two groups: TEAS group (n = 31) received TEAS by using a Hans acupoint nerve stimulator (HANS) model 200A with two output channels, 2-3 sessions per day, 30 minutes per session for 10 consecutive days. Electrical stimulation of alternating frequencies of 2- and 100-Hz with 3 second each, and with intensity of 10-15 mA was applied on Hegu (LI-4) and Laogong (PC-8) points on one hand, and Neiguan (PC-6) and Waiguan (SJ-5) points on the other forearm via electroconductive skin pads of 4 cm × 4 cm in size. The control group (n = 32) was treated with similar procedure except that the leads of the output of the stimulator was disconnected. Assessments of the severity of the withdrawal syndrome were conducted one day before and on each day during the whole treatment period of 10 days. Buprenorphin of 1 mg per day sublingually was provided to all subjects in the first two days, and then to those with withdrawal score over 20 in the following days. RESULTS The TEAS treatment dramatically alleviated the withdrawal syndrome during heroin detoxification. No significant difference was found in withdrawal scores between the two groups at the beginning of the observation. Withdrawal scores showed a more marked drop in TEAS group than the control starting from the second day, and maintained at a lower level for the whole course of treatment. The area under the curve of withdrawal score in TEAS group was only 40% of that in the control (P < 0.001, two way repeated measures analysis of variance), and the requirement of buprenorphine was only 10% of that in the control. No adverse effects were observed in either group. CONCLUSION TEAS of 2/100 Hz for 10 days in abrupt abstinence of the heroin addicts resulted in a marked reduction of the withdrawal syndrome as well as a reduced requirement for rescue opioids.

Re-exposure to morphine-associated context facilitated long-term potentiation in the vSUB-NAc glutamatergic pathway via GluN2B-containing receptor activation.

The glutamatergic projection from the ventral subiculum of the hippocampus (vSUB) to the nucleus accumbens (NAc) shell has been reported to play a key role in drug‐related behavior. The GluN2B subunit of N‐methyl‐D‐aspartate receptors (NMDARs) in the NAc can be selectively elevated after the retrieval of drug‐conditioned memory. However, whether the increased GluN2B‐containing NMDARs (GluN2B‐NMDARs) are able to alter the synaptic plasticity of the vSUB‐NAc glutamatergic pathway remains unclear. Here, we found that the long‐term potentiation (LTP) in the vSUB‐NAc pathway was facilitated and the GluN2B subunit protein level was elevated in synaptoneurosomes of the NAc shell, but not in the core, following morphine‐induced conditioned place preference (CPP) expression in rats. The facilitated LTP was prevented by the GluN2B‐NMDAR antagonist RO25‐6981. Also, a neurochemical disconnection following microinjection of RO25‐6981 into the NAc shell, plus microinfusion of GABA agonist baclofen and muscimol into the contralateral vSUB prevented the expression of morphine‐induced CPP. These findings suggest that the retrieval of drug‐associated memory potentiated synaptic plasticity in the vSUB‐NAc pathway, which was dependent on GluN2B‐NMDAR activation in the NAc shell. These findings provide a new explanation for the mechanisms that underlie the morphine‐associated‐context memory. The GluN2B‐NMDARs may be regarded as a potential target for erasing morphine‐related memory.

Erratum to “The possible involvement of endogenous ligands for mu-, delta- and kappa-opioid receptors in modulating morphine-induced CPP expression in rats” [Peptides 27 (12) (2006) 3307–3314]

Jing Liang , Yijing Li , Xingjie Ping , Peng Yu , Yanfang Zuo , Liuzhen Wu, Ji-Sheng Han , Cailian Cui * Neuroscience Research Institute and Department of Neurobiology, Peking University Health Science Center, Key Laboratory of Neuroscience, The Ministry of Education and Ministry of Public Health, 38 Xueyuan Road, Beijing 100083, PR China Bioorganic and Natural Products Laboratory, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA avai lable at www.sc iencedi rec t .com