Brain-derived neurotrophic factor and Bcl-2 expression in rat brain areas following chronic morphine treatment

The ventral tegmental area and the locus coeruleus are associated with psychological and physical dependence of opioid addiction. To date, very little is known about brain-derived neurotrophic factor （BDNF） and Bcl-2 gene and protein changes following morphine addiction. The present study utilized immunohistochemistry and in situ hybridization techniques, which revealed that there were increased BDNF levels, but decreased Bcl-2 levels in the prefrontal cortex, locus coeruleus, hippocampus, and the ventral tegmental area during morphine-dependence formation and abstinence. However, the levels of BDNF remained unchanged, and Bcl-2 expression was increased in the nucleus accumbens. These results showed that BDNF and Bcl-2 are involved in the development of morphine dependence, and precipitation of abstinence syndrome.

Sidiming attenuates morphine withdrawal syndrome and nitric oxide (synthase) levels in morphine-dependent rats and rhesus monkeys

The present study analyzed the effects of Sidiming, a Chinese herbal compound, on withdrawal syndrome, body weight loss, and serum levels of nitric oxide and its synthase in morphine- dependent rats and rhesus monkeys. These effects were compared with clonidine, an active control drug used for clinical treatment. Results showed that 4 and 8 g/kg Sidiming, respectively, significantly suppressed morphine withdrawal syndrome and reduced body mass loss in morphine-dependent rats. In addition, 2.4 and 4.8 g/kg Sidiming, respectively, significantly attenuated withdrawal syndrome in rhesus monkeys. High-dose Sidiming （8 g/kg in rats and 4.8 g/kg in rhesus monkeys） led to significantly inhibited serum levels of nitric oxide and its synthase in morphine-dependent rats and rhesus monkeys, which were greater than clonidine. These findings suggested that Sidiming treatment attenuated withdrawal syndrome in morphine-dependent rats and rhesus monkeys by inhibiting serum nitric oxide and its synthase.

Brain regional changes of guanine nucleotide binding protein-inhabitant 2 in acute and chronic morphine-tolerant and-dependent rats

BACKGROUND： Drug addiction involves two main central nervous systems, namely the dopamine and noradrenaline systems. These systems are primarily distributed in five brain regions： the ventral tegmental area, the nucleus accumbens, the prefrontal cortex, the hippocampus, and the locus coeruleus. OBJECTIVE： To investigate regional changes of guanine nucleotide binding protein-inhabitant 2 （Gi2） in dopaminergic and noradrenergic neurons in brains of morphine-tolerant and -dependent rats. DESIGN, TIME, AND SETTING： A randomized control study was performed at the Department of Neurobiology in the Second Military Medical University of Chinese PLA （Shanghai, China） between September 2002 and March 2004. MATERIALS： Thirty-six, healthy, male, Sprague-Dawley （SD） rats were used to establish morphine-dependent models. Morphine hydrochloride was a product of Shenyang First Pharmaceutical Factory （China）; naloxone hydrochloride was a product of Beijing Four-Ring Pharmaceutical Factory （China）; and α subunit of Gi2 antibody was offered by Santa Cruz Biotechnology, lnc （USA）. METHODS： Thirty-six SD rats were randomly divided into six groups （n = 6）： （1） acute morphine-dependent group, （2） acute abstinent group, （3） acute control group, （4） chronic morphine-dependent group, （5） chronic abstinent group, and （6） chronic control group. Rats in the acute morphine-dependent and the acute groups were injected with morphine （5 mg/kg）, one injection every two hours, for a total of eight injections. In the acute and chronic morphine-dependent rat models, morphine withdrawal syndrome was precipitated by an injection of naloxone （5 mg/kg）. Rats in the acute control group were given a peritoneal injection of physiological saline at the same administration time as the above two groups. Rats in the chronic morphine-dependent and chronic abstinent groups were injected with morphine three times per day. The administration dose on day 1 was initially 5 mg/kg at 20：00, which increased by 5 mg/kg at 8：00, 12：00, and 20：00 until day 7. On day 13, the dose continuously increased by 10 mg/kg until a chronic morphine-dependent rat model was successfully induced. Afterwards, the rats presented with withdrawal syndromes on naloxone （5 mg/kg） at 8：00 on the same day. Rats in the chronic control group were injected with physiological saline at the same time of the two chronic groups. MAIN OUTCOME MEASURES： The concentration of Gi2 protein in the five brain regions （ventral tegmental area, nucleus accumbens, prefrontal cortex, locus coeruleus, and hippocampus） was detected by immunohistochemistry. RESULTS： In the acute morphine-dependent and acute abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, compared to the acute control group （P 〈 0.01）, while no obvious changes were detected in other brain regions. In the chronic morphine-dependent and chronic abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, but significantly increased in the locus coeruleus （P 〈 0.01 ） compared to the chronic control group. CONCLUSION： Morphine dependence and tolerance may induce obvious reductions of Gi2 protein levels in the nucleus accumbens of rats. Chronic morphine dependence desensitizes the homologous neurons.

Effect of reward alteration following acupuncture for morphine withdrawal rats on neuronal discharges in the ventral medial prefrontal cortex

Objective：To observe the effect of reward alteration following acupuncture for morphine withdrawal rats on the behavior and neuronal discharges in the medial prefrontal cortex （mPFC）. Methods：The Sprague-Dawley （SD） rats were randomly allocated into a model group, a confinement group, an electroacupuncture （EA） group, and a control group. Rats with morphine addiction were made by intraperitoneal injection of naloxone （same dose injection of saline for rats in the control group）, followed by a 2-week morphine withdrawal. Acupuncture and confinement were completed during the morphine withdrawal period. Upon withdrawal, the rats received conditioned place preference （CPP） training and open field test. The multi-channel neural signal processor was used in the electrophysiological experiment to measure the neuronal discharges in different subareas of prefrontal cortex in CPP box and aversion box. Results：Rats in the model group and the confinement group spent longer period of time in CPP box than those in the EA group and the control group （allP〈0.01）; there was no statistically significant difference between the EA group and the control group. The total distances of movement by rats in the model group and the confinement group were longer than those in the EA group and the control group （allP〈0.01）. The mPFC neuronal discharge frequencies were compared between morphine preference box and aversion box. The mPFC neuronal discharge frequencies in the model group and the confinement group were higher than those in the EA group and the control group （allP〈0.05）; there was no statistically significant difference between the EA group and the control group. Conclusion：Acupuncture can effectively interfere with the reward alteration following morphine withdrawal, possibly because of its involvement with the mPFC neuronal discharges.

Changes of Adenylate Cyclase and Guanylate Cyclase in the Frontal Cortex,Lenticula,Corpus Amygdaloideum,and Hippocampus in Morphine‑dependent Rats

To detect the changes of adenylate cyclase(AC)and guanylate cyclase(GC)in the four cerebral regions that are concerned with psychogenic dependence of morphine in rats,including the frontal cortex,lenticula,corpus amygdaloideum,and hippocampus.To discuss the relation between the expressions of AC and GC with the psychogenic dependence on morphine.Different periods of morphine‑dependent rat models were established,and enzyme histochemistry was used to detect the variations of AC and GC in four cerebral regions.Compared with the control group,AC and GC in all the morphine‑dependent groups increased.The data indicated that the amounts of AC and GC were significantly different between the morphine‑dependent groups and the control group when tested at periods of 1 week,2 weeks,4 weeks,and 8 weeks(P<0.05 or P<0.01).There were significant differences when comparing the 1‑week group with the 2‑week,4‑week,and 8‑week groups(P<0.05 or P<0.01).There were significant differences when comparing the 2‑week dependent group with the 4‑week dependent group or the 8‑week dependent group(P<0.05 or P<0.01).The activities of AC and GC increased in four cerebral regions of morphine‑dependent rats.The psychogenic dependence on morphine appears to be closely linked to the upgrade of AC and GC.

Inhibition of the reinstatement of morphine-induced place preference in rats by high-frequency stimulation of the bilateral nucleus accumbens

Background Opiate addiction remains intractable in a large percentage of patients, and relapse is the biggest hurdle to recovery. Many studies have identified a central role of the nucleus accumbens （NAc） in addiction. Deep brain stimulation （DBS） has the advantages of being reversible, adjustable, and minimally invasive, and it has become a potential neurobiological intervention for addiction. The purpose of our study was to investigate whether high-frequency DBS in the NAc effectively attenuates the reinstatement of morphine seeking in morphine-primed rats. Methods A morphine-dependent group of rats was given increasing doses of morphine during conditioned place preference training. A control group of rats was given equal volumes of saline. After the establishment of this model, withdrawal syndromes were precipitated in these two groups by administering naloxone, and the differences in withdrawal symptoms between the groups were analyzed. Electrodes for DBS were implanted in the bilateral shell of the NAc in the experimental group. The rats were stimulated daily in the NAc for 5 hours per day over 30 days. Changes in the conditioned place preference test and withdrawal symptoms in the rats were investigated and place navigation studies were performed using the Morris water maze. The data were assessed statistically with one-way analysis of variance （ANOVA） followed by Tukey＇s tests for multiple post hoc comparisons. Results High-frequency stimulation of the bilateral NAc prevented the morphine-induced reinstatement of morphine seeking in the conditioned place preference test. The time spent in the white compartment by rats following 30 days of DBS （（268.25±25.07） seconds） was not significantly different compared with the time spent in the white compartment after relapse was induced by morphine administration （（303.29±34.22） seconds）. High-frequency stimulation of the bilateral NAc accelerated the innate decay of drug craving in morphine-dependent rats without significantly influencing learning and memory. Conclusion Bilateral high-frequency stimulation of the shell of the NAc may be useful as a novel therapeutic modality for the treatment of severe morphine addiction.