Continuous infusion versus intermittent bolus dosing of morphine: a comparison of analgesia, tolerance, and subsequent voluntary morphine intake.

Improved utilization of continuous or intermittent opioid administration in pain treatment necessitates a comparison of the antinociceptive effect and tolerance of these two treatment methods. More importantly, the effect of treatment method on subsequent opioid consumption has not been directly compared, although it is widely assumed that continuous opioid treatment may produce lower addictive liability relative to intermittent opioid treatment. In this study, we compared the antinociceptive effect and tolerance of morphine in rats that received repeated injection (10 mg/kg twice daily for 7 days) or continuous infusion (20 mg/kg daily for 7 days) subcutaneously and the self-administration of intravenous morphine in these rats after 7 days of withdrawal.

DBS of nucleus accumbens on heroin seeking behaviors in self-administering rats.

Background: Surgical ablation of select brain areas has been frequently used to alleviate psychological dependence on opiate drugs in certain countries. However, ablative brain surgery was stopped in China in 2004 due to the related ethical controversy and possible side effects. Deep brain stimulation (DBS), a less invasive, reversible and adjustable process of neuromodulation, was adopted to attenuate relapses in studies of drug addiction.

Lack of effect of habenula lesion on heroin self-administration in rats.

We examined the effects of bilateral electric lesion of the habenula (Hb) on the acquisition and maintenance of heroin self-administration. The rats were trained to self-administer heroin (0.05 mg/kg/infusion) under FR1 schedule in daily 4h sessions.

[Effect of electroacupuncture on drug-seeking behaviors induced by heroin priming and FosB expression in relevant brain regions].

Objective: To explore the effect of electroacupuncture on heroin seeking behavior and FosB expression in relevant brain regions.

Methods: Rat model of heroin relapse behaviors was developed with progressive fixed ratio program,and model rats were randomly divided into 3 groups: a restraint group, a needle retention group, and a electroacupuncture group. The heroin seeking behavior was elicited by a small dose of heroin.

Increased c-Fos expression in the medial part of the lateral habenula during cue-evoked heroin-seeking in rats.

Conditioned environmental stimuli are known to be important determinants of drug seeking behavior. c-Fos, the protein product of the protooncogene c-Fos, is expressed in neurons when there are drug-associated cue-induced drug-seeking behaviour. Therefore, its expression could serve as a marker of regional neuronal activation.

The dissociation of heroin-seeking patterns induced by contextual, discriminative, or discrete conditioned cues in a model of relapse to heroin in rats.

Rationale: The role of heroin-related stimuli in motivating the resumption of heroin use is not fully understood.

Objectives: The objective was to characterize the relative importance of drug-related contextual stimuli, discriminative stimuli (DS), or discrete conditioned stimuli (CSs) on drug seeking when rats were reintroduced into the operant context after withdrawal.

Methods: Nose-poke responding by male rats was reinforced with intravenous heroin (0.

Motivation of heroin-seeking elicited by drug-associated cues is related to total amount of heroin exposure during self-administration in rats.

Conditioned stimuli (CSs) previously associated with heroin are critically involved in activating long-lasting relapse and compulsive drug seeking. This study examined the magnitude of heroin seeking induced by drug-related cues in relation to the total amount of drug exposure during training. Five groups of male Sprague-Dawley rats (n=6/group) were trained by the nose-poking response to self-administer different doses of heroin (0, 0.

Low dose of heroin inhibits drug-seeking elicited by cues after prolonged withdrawal from heroin self-administration in rats.

Environmental stimuli and conditioned cues associated with heroin can induce drug-seeking behavior, but how heroin lapse interacts with cues is unclear. Rats were trained to nose-poke for i.v.

[mRNA expression of muscarinic receptors in spinal cord and brainstem in morphine dependent rats].

Aim: To observe mRNA expression of muscarinic acetylcholine receptors in spinal cord and brainstem in morphine dependent or withdrawal rats.

Methods: The mRNA expression level of m1, m2, m3, m4 and m5 were determined by RT-PCR, the beta-actin mRNA expression was used as internal control.

Results: The mRNA level of m1, m2, m3, m4 and m5 in spinal cord and m1 and m2 in brainstem were increased significantly during morphine dependence, and the levels of m1, m2, m3 and m4 in spinal cord and m1 in brainstem were decreased 1 h after the injection of naloxone (4 mg.