Sertindole antagonizes morphine-, cocaine-, and methamphetamine-induced place preference in the rat

Effects of adolescent methylphenidate administration on methamphetamine conditioned place preference in an animal model of attention-deficit/hyperactivity disorder: Examination of potential sex differences

BACKGROUND

Individuals with attention-deficit/hyperactivity disorder (ADHD) are more likely to be diagnosed with a substance use disorder; however, the effects of long-term psychostimulant treatment on addiction are mixed. Preclinical studies are useful for further elucidating the relationship between ADHD and addiction-like behaviors, but these studies have focused on male subjects only. The goal of the current study was to determine if early-life administration of methylphenidate (MPH) augments methamphetamine (METH) conditioned place preference (CPP) and/or potentiates reinstatement of CPP in both male and female rats.

METHODS

Male and female spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) received either MPH (1.5mg/kg; p.o.) or vehicle (1.0ml/kg) during adolescence (postnatal day [PND] ~29-57). Two weeks after cessation of MPH treatment, rats were tested for METH CPP (1.0mg/kg or 2.0mg/kg; s.c.). Rats were then given extinction sessions. Once rats met extinction criteria, they were tested for reinstatement of CPP following a priming injection of METH (0.25mg/kg; s.c.).

RESULTS

All groups developed METH CPP, except vehicle-treated SHR males and vehicle-treated WKY females conditioned with the higher dose of METH (2.0mg/kg). Female SHRs treated with MPH showed greater reinstatement of METH CPP compared to female SHRs treated with vehicle. Adolescent MPH treatment did not augment the locomotor-stimulant effects of METH in adulthood.

CONCLUSIONS

These results demonstrate the importance of considering biological sex when prescribing psychostimulant medications for ADHD as long-term MPH administration may increase the risk of continued drug use in females with ADHD following a period of abstinence.

Place preferences induced by electrical stimulation of the external lateral parabrachial subnucleus in a sequential learning task: Place preferences induced by NLPBe stimulation

It is known that electrical stimulation of the external lateral parabrachial nucleus (NLPBe) can sustain concurrent taste and place learning. Place preferences can be learned through different procedures. Previous studies demonstrated that electrical stimulation of the PBNLe can generate aversive and preference place learning using concurrent procedures. In the concurrent procedure, the animals can move freely in the maze, and intracranial electrical stimulation is associated with their voluntary stay in one of the two maze compartments. However, the rewarding properties of most stimuli, whether natural or drugs of abuse, have usually been investigated using the sequential procedure, in which animals are confined while receiving the unconditioned stimulus and then undergo a choice test without stimulation in a later phase. This study examined whether this stimulation can sustain place preference learning in sequential tasks. Results demonstrated that place preferences can also be induced by the electrical stimulation of the NLBe using sequential procedures. These findings suggest that the NLPBe may form part of a brain reward axis that shares certain characteristics with those observed in the processing of natural rewarding agents and especially of drugs of abuse.

Effects of propofol on conditioned place preference in male rats: Involvement of nitrergic system

BACKGROUND

Drug-induced conditioned place preference (CPP) is linked to the addictive properties of the drug used. The number of studies that have investigated the effects of propofol on CPP is limited. Research findings suggest that nitric oxide (NO) might play an important role in substance use disorders.

OBJECTIVES

The present study sought to investigate the role of the nitrergic system on the rewarding effects of propofol by using the CPP protocol in rats.

METHODS

The experiment followed habituation, pre-conditioning, conditioning, and post conditioning sessions. Male Wistar albino rats weighing 240-290 g were divided into eight groups: control (saline), propofol (10, 20, and 40 mg/kg), the NO synthase (NOS) inhibitor N^G-nitro-L-arginine methyl ester (L-NAME) alone (30 and 60 mg/kg), and in combination with propofol (30 and 60 mg/kg L-NAME plus 40 mg/kg propofol) (n = 8 for each group). The CPP effects of propofol, L-NAME, saline, and their combinations were evaluated. All the drug and saline administrations were performed by intraperitoneal (ip) injections.

RESULTS

Propofol (10-40 mg/kg) produced CPP that was statistically significant relative to saline. Propofol-induced CPP was significantly reversed by pretreatment with L-NAME. When administered alone, L-NAME did not produce CPP and also did not produce any significant change on locomotor activity of naïve rats.

CONCLUSION

Our results suggest that propofol produces CPP effects in rats and that NO-related mechanisms may be responsible for propofol-induced CPP. Thus, propofol might have the potential to be addictive, and this possibility should be considered during clinical applications of this drug.

Blockade of patch-based μ opioid receptors in the striatum attenuates methamphetamine-induced conditioned place preference and reduces activation of the patch compartment

The behavioral effects of methamphetamine (METH) are mediated by the striatum, which is divided into the patch compartment, which mediates limbic and reward functions, and the matrix compartment, which mediates sensorimotor tasks. METH treatment results in repetitive behavior that is related to enhanced relative activation of the patch versus the matrix compartment. The patch, but not the matrix compartment contains a high density of μ opioid receptors, and localized blockade of patch-based μ opioid receptors attenuates METH-induced patch-enhanced activity and repetitive behaviors. Numerous studies have examined patch-enhanced activity and the contribution of patch-associated μ opioid receptors to METH-induced repetitive behavior, but it is not known whether patch-enhanced activity occurs during METH-mediated reward, nor is it known if patch-based μ opioid receptors contribute to METH reward. The goals of this study were to determine if blockade of patch-based μ opioid receptors alters METH-induced conditioned place preference (CPP), as well activation of the patch and matrix compartments following METH-mediated CPP. A biased conditioning paradigm was used to assess CPP, and conditioning occurred over an 8-d period. Animals were bilaterally infused in the striatum with the μ-specific antagonist CTAP or vehicle prior to conditioning. Animals were tested for preference 24h after the last day of conditioning, sacrificed and the brains processed for immunohistochemistry. Blockade of patch-based μ opioid receptors reduced METH-induced CPP, and reduced patch-enhanced c-Fos expression in the striatum following METH-mediated CPP. These data indicate that patch-enhanced activity is associated with METH-mediated reward and patch-based μ opioid receptors contribute to this phenomenon.

Mephedrone, methylone and 3,4-methylenedioxypyrovalerone (MDPV) induce conditioned place preference in mice

During the last decade, there has been a worldwide increase in popularity and abuse of synthetic cathinones. Common ingredients of the so-called bath salts include mephedrone, methylone and 3,4-methylenedioxypyrovalerone (MDPV). Relatively little information about the pharmacology and addiction potential of these drugs is available. We used the conditioned place preference (CPP) paradigm to explore the reinforcing effects of three different synthetic cathinones. The primary aim of this study was to investigate whether mephedrone, methylone and MDPV induce CPP in mice. The secondary aims were to investigate a possible dose-response CPP and whether the synthetic cathinones induce higher CPP than amphetamine at equal dose. C57BL/6 mice were conditioned to mephedrone, methylone, MDPV and amphetamine at doses of 0.5, 2, 5, 10 or 20 mg/kg (i.p.). During the conditioning, the mice received two training sessions per day for 4 days. All four tested drugs showed a significant place preference compared with controls. Mice conditioned with MDPV (5 and 10 mg/kg) displayed a greater preference score compared to mice conditioned with amphetamine (5 and 10 mg/kg). Our findings show that mephedrone, methylone and MDPV produce CPP equal or higher than amphetamine strongly suggesting addictive properties. Given the public health concern of abuse, future pharmacological studies are necessary to fully understand the effects of these drugs.

Metabolic profiling of urine and blood plasma in rat models of drug addiction on the basis of morphine, methamphetamine, and cocaine-induced conditioned place preference

The metabolic profiles of urine and blood plasma in drug-addicted rat models based on morphine (MOR), methamphetamine (MA), and cocaine (COC)-induced conditioned place preference (CPP) were investigated. Rewarding effects induced by each drug were assessed by use of the CPP model. A mass spectrometry (MS)-based metabolomics approach was applied to urine and plasma of MOR, MA, and COC-addicted rats. In total, 57 metabolites in plasma and 70 metabolites in urine were identified by gas chromatography-MS. The metabolomics approach revealed that amounts of some metabolites, including tricarboxylic acid cycle intermediates, significantly changed in the urine of MOR-addicted rats. This result indicated that disruption of energy metabolism is deeply relevant to MOR addiction. In addition, 3-hydroxybutyric acid, L-tryptophan, cystine, and n-propylamine levels were significantly changed in the plasma of MOR-addicted rats. Lactose, spermidine, and stearic acid levels were significantly changed in the urine of MA-addicted rats. Threonine, cystine, and spermidine levels were significantly increased in the plasma of COC-addicted rats. In conclusion, differences in the metabolic profiles were suggestive of different biological states of MOR, MA, and COC addiction; these may be attributed to the different actions of the drugs on the brain reward circuitry and the resulting adaptation. In addition, the results showed possibility of predict the extent of MOR addiction by metabolic profiling. This is the first study to apply metabolomics to CPP models of drug addiction, and we demonstrated that metabolomics can be a multilateral approach to investigating the mechanism of drug addiction.

Differential effects of the ascorbyl and tocopheryl derivative on the methamphetamine-induced toxic behavior and toxicity

A previous study showed that high doses of methamphetamine induce self-injurious behavior (SIB) in rodents. Furthermore, the combination of methamphetamine and morphine increased lethality in mice. We recently surmised that the rise in SIB and mortality induced by methamphetamine and/or morphine may be related to oxidative stress. The present study was designed to determine whether an antioxidant could inhibit SIB or mortality directly induced by methamphetamine and/or morphine. The SIB induced by 20mg/kg of methamphetamine was abolished by the administration of Na L-ascorbyl-2-phosphate (APS: 300 mg/kg), but not Na DL-alpha-tocopheryl phosphate (TPNa: 200mg/kg). In contrast, APS (300 mg/kg) and TPNa (200mg/kg) each significantly attenuated the lethality induced by methamphetamine and morphine. The present study showed that the signal intensity of superoxide adduct was increased by 20mg/kg of methamphetamine in the heart and lungs, and methamphetamine plus morphine tended to increase superoxide adduct in all of the tissues measured by ESR spin trap methods. Adduct signal induced in brain by methamphetamine administration increased in significance, but in mouse administrated methamphetamine plus morphine. There are differential effects of administration of methamphetamine and coadministration of methamphetamine plus morphine on adduct signal. These results suggest that APS and TPNa are effective for reducing methamphetamine-induced toxicity and/or toxicological behavior. While APS and TPNa each affected methamphetamine- and/or morphine-induced toxicology and/or toxicological behavior, indicating that both drugs have antioxidative effects, their effects differed.

The effect of l-stepholidine, a novel extract of Chinese herb, on the acquisition, expression, maintenance, and re-acquisition of morphine conditioned place preference in rats

The effect of L-stepholidine (SPD), a novel alkaloid extract of the Chinese herb Stephania with partial dopamine D1 receptor agonistic and D2 receptor antagonistic dual actions, on morphine conditioned place preference (CPP) was studied. Daily injection of morphine (10 mg/kg, i.p.) for 6 days induced CPP in rats, and daily treatment with SPD at 10 or 20 mg/kg before morphine injection dose-dependently attenuated morphine-induced CPP. On the day following acquisition of morphine CPP, a single administration of SPD at 10 or 20 mg/kg failed to block the expression of CPP. However, daily administration of SPD at 20 mg/kg for 7 days attenuated the maintenance of CPP. Morphine-induced CPP extinguished after a 21-day saline training and then a single injection of morphine (3 mg/kg, i.p.) induced re-acquisition of morphine CPP; however, pretreatment with SPD at 10 or 20 mg/kg 30 min before morphine injection dose-dependently blocked morphine (3 mg/kg, i.p.)-induced re-acquisition of morphine CPP. Furthermore, our data indicate that SPD had no effect on food-induced CPP or state-dependent learning, suggesting that the observed effect of SPD does not result from an inhibition of general learning ability. These results demonstrate that SPD can inhibit acquisition, maintenance, and re-acquisition of morphine conditioned place preference and suggest its potential for treatment of opioid addiction.

Morphine-conditioned single-trial place preference: role of nucleus accumbens shell dopamine receptors in acquisition, but not expression

RATIONALE

A large body of evidence indicates an involvement of the mesolimbic dopamine (DA) pathway innervating the ventral striatum in the motivational effects of drug abuse.

OBJECTIVE

The goal of the study is to clarify the role of DA D1 and D2 receptors of the rat nucleus accumbens (NAc) shell and core in the motivational effects of morphine as studied by conditioned place preference (CPP).

METHODS

The effect of the intracerebral infusion of DA antagonists specific for DA D1 (SCH 39166) and D2 receptors (L-sulpiride) was studied in a single-trial place conditioning paradigm with fixed assignment of the drug to the unpreferred compartment.

RESULTS

Morphine induced significant CPP at all the doses tested (0.5, 1.0, and 2.0 mg/kg, subcutaneously). A dose of 1.0 mg/kg was selected for further studies. Intra-NAc shell infusion of SCH 39166 and L-sulpiride at doses of 25 and 50 ng/1 microl per side impaired the acquisition of CPP by morphine. No effect was observed at 12.5 ng/1 microl per side. Intra-NAc core infusion of SCH 39166 (12.5, 25, and 50 ng/1 microl per side) did not affect the acquisition of morphine-induced CPP, while L-sulpiride (12.5, 25, and 50 ng/1 microl per side) impaired CPP acquisition only at the dose of 50 ng/1 microl per side. No effect on morphine-induced CPP was observed when the DA antagonists were infused into the NAc shell or core 10 min before the test session.

CONCLUSION

These results indicate that DA D1 and D2 receptors in the NAc shell are involved in the acquisition of morphine-induced CPP.

Effects of oxazepam on methamphetamine-induced conditioned place preference

Our laboratory has been investigating the role for the hypothalamo-pituitary-adrenal (HPA) axis and benzodiazepines in the behavioral effects of cocaine for several years now. The following represents our initial investigation of the influence of benzodiazepines on methamphetamine reward using conditioned place preference. In these experiments, methamphetamine (0.5 mg/kg ip) resulted in a robust conditioned place preference that was attenuated when the rats were pretreated with oxazepam (10 mg/kg ip) on the day of preference testing. These data suggest a potential role for benzodiazepines in the behavioral effects of methamphetamine. Additional research will be necessary to determine if the nature of these effects is similar with what has been observed with cocaine.

Suppression of morphine-induced conditioned place preference by l-12-chloroscoulerine, a novel dopamine receptor ligand

The effect of l-12-chloroscoulerine (l-CSL), a novel ligand with dual dopamine D1 receptor agonistic and D2 receptor antagonistic actions, on the development of morphine-induced conditioned place preference (CPP) was investigated in mice. Morphine (10 mg/kg)-induced place preference was dose dependently suppressed by coadministration of l-CSL (5, 10 and 20 mg/kg), which induced neither place preference nor place aversion when administered alone at a dose of 20 mg/kg. The D1 receptor antagonist SCH23390 (0.1 mg/kg) suppressed, whereas the D2 receptor agonist (+/-)-2-(N-phenylethyl-N-propyl)-amino-5-hydroxytetralin (PPHT) (0.5 mg/kg) had no influence on the development of morphine-induced place preference. However, SCH23390 (0.1 mg/kg) did not affect, whereas PPHT (0.5 mg/kg) reversed the suppressive effect of l-CSL on the development of morphine-induced place preference. These results indicate that l-CSL suppresses the development of place preference of morphine by blocking D2 receptors.

Drug dependence: neuropharmacology and management

This overview has attempted to highlight the brain regions associated with reward, and the pathways and neurotransmitters responsible for communication between these regions. Work conducted in this field has shown that stimulants and opioids, despite interactions with different receptor types and different neurotransmitter reuptake transporters, appear to share a common action on brain reward pathways. Their effects on these pathways (the distinct brain regions making up the mesocorticolimbic dopaminergic system) are predominantly mediated through changes in dopamine neurotransmission, and compounds aimed at selectively modulating these effects may form the basis of drugs to treat addiction. Other transmitters such as GABA, acetylcholine and serotonin inevitably have a role to play in reward, although at present the exact nature of their effects remains unclear. Diverging from manipulating the CNS directly as a management strategy for dependence, it might be possible to exploit the immune system to prevent administered psychostimulants penetrating the brain, but antibody saturation and specificity are problematic.

Effects of dopamine antagonists with different receptor blockade profiles on morphine-induced place preference in male mice

The effects of dopamine (DA) antagonists with different selectivity for the DA receptors (SCH 23390, 0.5, 0.25, 0.125 mg/kg; haloperidol, 0.2, 0.1 mg/kg; raclopride, 1.2, 0.6, 0.3 mg/kg; risperidone, 0.4, 0.2, 0.1 mg/kg; U-99194A maleate, 40, 20 mg/kg; clozapine, 2.5, 1.25, 0.625 mg/kg) on the acquisition of place conditioning and morphine-induced conditioned place preference (CPP) were explored in male mice. Morphine (40 mg/kg) produced CPP while SCH 23390, haloperidol and clozapine (highest dose) and risperidone (lowest dose) produced conditioned place aversion (CPA). Raclopride and U-99194A maleate did not produce CPP or CPA. Morphine-induced CPP was reversed by the administration of SCH 23390 and risperidone (all doses), haloperidol (highest dose) and raclopride and clozapine (intermediate and lowest doses). U-99194A maleate did not reverse morphine-induced CPP. These results suggest that the conditioned rewarding effects of morphine are mediated by the different subtypes of DA receptors.

Measuring reward with the conditioned place preference paradigm: a comprehensive review of drug effects, recent progress and new issues

This review gives an overview of recent findings and developments in research on brain mechanisms of reward and reinforcement from studies using the place preference conditioning paradigm, with emphasis on those studies that have been published within the last decade. Methodological issues of the paradigm (such as design of the conditioning apparatus, biased vs unbiased conditioning, state dependency effects) are discussed. Results from studies using systemic and local (intracranial) drug administration, natural reinforcers, and non-drug treatments and from studies examining the effects of lesions are presented. Papers reporting on conditioned place aversion (CPA) experiments are also included. A special emphasis is put on the issue of tolerance and sensitization to the rewarding properties of drugs. Transmitter systems that have been investigated with respect to their involvement in brain reward mechanisms include dopamine, opioids, acetylcholine, GABA, serotonin, glutamate, substance P, and cholecystokinin, the motivational significance of which has been examined either directly, by using respective agonist or antagonist drugs, or indirectly, by studying the effects of these drugs on the reward induced by other drugs. For a number of these transmitters, detailed studies have been conducted to delineate the receptor subtype(s) responsible for the mediation of the observed drug effects, particularly in the case of dopamine, the opioids, serotonin and glutamate. Brain sites that have been implicated in the mediation of drug-induced place conditioning include the 'traditional' brain reward sites, ventral tegmental area and nucleus accumbens, but the medial prefrontal cortex, ventral pallidum, amygdala and the pedunculopontine tegmental nucleus have also been shown to play important roles in the mediation of place conditioning induced by drugs or natural reinforcers. Thus, although the paradigm has also been criticized because of some inherent methodological problems, it is clear that during the past decade place preference conditioning has become a valuable and firmly established and very widely used tool in behavioural pharmacology and addiction research.

Continued trends in the conditioned place preference literature from 1992 to 1996, inclusive, with a cross-indexed bibliography

In light of the overwhelming response to the previous publication in Neuroscience and Biobehavioral Reviews (1993, 17, 21-41) regarding trends in place conditioning (either preference or aversion), the present work constitutes a five-year follow-up to review the empirical research in this behavioral paradigm from 1992 to 1996, inclusively. The behavioral technique has grown as indicated by the number of publications over the last five years which equals those authored over the 35 years covered by our last survey. The previous work used descriptive statistics to explore topical issues, whereas the present work discusses trends since that time and hopes to provide an exhaustive bibliography of the CPP literature, including articles, published abstracts, book chapters and reviews, as well as providing a cross-index of identified key words/drugs tested.