Conditioned place aversion produced by dopamine release inhibition

Distinct signals in medial and lateral VTA dopamine neurons modulate fear extinction at different times

Dopamine (DA) neurons are thought to encode reward prediction error (RPE), in addition to other signals, such as salience. While RPE is known to support learning, the role of salience in learning remains less clear. To address this, we recorded and manipulated VTA DA neurons in mice during fear extinction. We applied deep learning to classify mouse freezing behavior, eliminating the need for human scoring. Our fiber photometry recordings showed DA neurons in medial and lateral VTA have distinct activity profiles during fear extinction: medial VTA activity more closely reflected RPE, while lateral VTA activity more closely reflected a salience-like signal. Optogenetic inhibition of DA neurons in either region slowed fear extinction, with the relevant time period for inhibition differing across regions. Our results indicate salience-like signals can have similar downstream consequences to RPE-like signals, although with different temporal dependencies.

Increased dopamine receptor activity in the nucleus accumbens shell ameliorates anxiety during drug withdrawal

A number of lines of evidence suggest that negative emotional symptoms of withdrawal involve reduced activity in the mesolimbic dopamine system. This study examined the contribution of dopaminergic signaling in structures downstream of the ventral tegmental area to withdrawal from acute morphine exposure, measured as potentiation of the acoustic startle reflex. Systemic administration of the general dopamine receptor agonist apomorphine or a cocktail of the D1-like receptor agonist SKF82958 and the D2-like receptor agonist quinpirole attenuated potentiated startle during morphine withdrawal. This effect was replicated by apomorphine infusion into the nucleus accumbens shell. Finally, apomorphine injection was shown to relieve startle potentiation during nicotine withdrawal and conditioned place aversion to morphine withdrawal. These results suggest that transient activation of the ventral tegmental area mesolimbic dopamine system triggers the expression of anxiety and aversion during withdrawal from multiple classes of abused drugs.

Dual role of medial A10 dopamine neurons in affective encoding

Increasing evidence suggests that the activation of medial A10 neurons mediates positive affective encoding. However, little is known about the functions of the inhibition of midbrain dopamine neurons. Here we show evidence suggesting that the inhibition of medial A10 neurons mediates a negative affective state, leading to negative affective encoding, whereas blunting the activation of medial A10 neurons disrupts positive affective encoding involving food reward. We used a microinjection procedure, in which the D(2) dopamine receptor agonist quinpirole was administered into the cell body region of the dopamine neurons, a procedure that reduces dopamine cell firing. Microinjections of quinpirole into the posteromedial ventral tegmental area, but not its more lateral counterparts, led to conditioned place aversion. Quinpirole administration to this site also decreased food intake and basal dopamine concentration in the ventromedial striatum, a major projection area of medial A10 neurons. In addition, moderate quinpirole doses that did not lead to conditioned place aversion or disrupt food intake abolished food-conditioned place preference, suggesting that blunting dopamine impulse activity in response to food reward disrupts positive affective encoding in associated external stimuli. Our data support the hypothesis that activation of medial A10 dopamine neurons mediates a positive affective state, leading to positive affective encoding, while their inhibition mediates a negative affective state, leading to negative affective encoding. Together with previous findings, we propose that medial A10 neurons are an important component of the mechanism via which animals learn to avoid negative incentive stimuli.

Monoamine oxidase inhibition dramatically prolongs the duration of nicotine withdrawal-induced place aversion

BACKGROUND

Long-lasting effects of withdrawal from nicotine are hypothesized to contribute to relapse and persistence of tobacco habits, and significant evidence supports a role of monoamine oxidase inhibitors (MAOI) contained in cigarette smoke as potent modulators of the rewarding effects of tobacco.

METHODS

With quantification of somatic signs of withdrawal and the place aversion conditioning paradigm, we assessed the effects of MAOI pretreatment on both somatic and aversive motivational components of mecamylamine-induced nicotine withdrawal in rats rendered dependent on nicotine by the subcutaneous implantation of osmotic minipumps (vehicle or nicotine tartrate 9 mg/kg/day).

RESULTS

In nicotine-infused rats, mecamylamine induced a place aversion that lasted 6 weeks. When nicotine-infused rats were also treated with a MAOI, mecamylamine-induced conditioned place aversion persisted for at least 8 months of abstinence. The MAOI treatment slightly decreased ratings of somatic signs induced by mecamylamine administration but had no effect on the threshold or the magnitude of mecamylamine-induced conditioned place aversion.

CONCLUSIONS

These results show that MAOI pretreatment induces a long-lasting conditioned placed aversion associated with nicotine withdrawal, possibly through a potentiation of learning and memory process, and provides some indications on protracted abstinence that might be useful for delineating the neurobiological substrate of relapse.

Delta9-tetrahydrocannabinol decreases somatic and motivational manifestations of nicotine withdrawal in mice

The possible interactions between Delta9-tetrahydrocannabinol (Delta9-THC) and nicotine remain unclear in spite of the current association of cannabis and tobacco in humans. The aim of the present study was to explore the interactions between these two drugs of abuse by evaluating the consequences of Delta9-THC administration on the somatic manifestations and the aversive motivational state associated with nicotine withdrawal in mice. Acute Delta9-THC administration significantly decreased the incidence of several nicotine withdrawal signs precipitated by mecamylamine or naloxone, such as wet-dog-shakes, paw tremor and scratches. In both experimental conditions, the global withdrawal score was also significantly attenuated by acute Delta9-THC administration. This effect of Delta9-THC was not due to possible adaptive changes induced by chronic nicotine on CB1 cannabinoid receptors, as the density and functional activity of these receptors were not modified by chronic nicotine administration in the different brain structures investigated. We also evaluated the consequences of Delta9-THC administration on c-Fos expression in several brain structures after chronic nicotine administration and withdrawal. c-Fos was decreased in the caudate putamen and the dentate gyrus after mecamylamine precipitated nicotine withdrawal. However, acute Delta9-THC administration did not modify c-Fos expression under these experimental conditions. Finally, Delta9-THC also reversed conditioned place aversion associated to naloxone precipitated nicotine withdrawal. Taken together, these results indicate that Delta9-THC administration attenuated somatic signs of nicotine withdrawal and this effect was not associated with compensatory changes on CB1 cannabinoid receptors during chronic nicotine administration. In addition, Delta9-THC also ameliorated the aversive motivational consequences of nicotine withdrawal.

Involvement of dopamine D1 receptors of the central amygdala on the acquisition and expression of morphine-induced place preference in rat

In the present study, the effects of intra-central amygdala (CeA) injection of dopamine D1 receptor agonist and antagonist on morphine-induced conditioned place preference (CPP) were investigated in male Wistar rats. Our data showed that subcutaneous (s.c.) injection of morphine sulphate (0.5-10 mg/kg) significantly increased the time spent in the drug-paired compartment in a dose-dependent manner. Intra-CeA administration of the dopamine D1 receptor agonist, SKF 38393 (2 and 4 micro g/rat) with an ineffective dose of morphine (0.5 mg/kg), elicited a significant conditioned place preference. On the other hand, a single dose of SKF 38393 (2 micro g/rat, intra-CeA) in combination with the lower doses (0.5 and 2.5 mg/kg), but not with the higher doses of morphine potentiated morphine-induced CPP. Furthermore, intra-CeA administration of the dopamine D1 receptor antagonist, SCH 23390 (0.5-1 micro g/rat) decreased the acquisition of conditioned place preference induced by morphine (7.5 mg/kg). The response of SKF 38393 was decreased by SCH 23390 (0.75 micro g/rat). SKF 38393 or SCH 23390 by themselves did not elicit any effect on place conditioning. On the other hand, intra-CeA administration of SKF 38393 or SCH 23390 significantly decreased the expression of morphine (7.5 mg/kg)-induced place preference. SKF 38393 or SCH 23390 injections into the CeA had no effects on the locomotor activity on the test sessions. The results indicate that the dopamine D1 receptors in the CeA may be involved in the acquisition and expression of morphine-induced place preference.

Mecamylamine-precipitated nicotine-withdrawal aversion in Lewis and Fischer 344 inbred rat strains

Many studies have indicated that Lewis and Fischer 344 inbred rat strains show marked differences in behavioral responses to abused drugs. In the present study, we sought to determine whether these two strains of rats show different responses in mecamylamine-precipitated nicotine-withdrawal aversion using the conditioned place preference paradigm. Rats were treated subcutaneously with 10 mg/kg/day nicotine for 7 days using an osmotic minipump. After chronic nicotine infusion, the nicotinic receptor antagonist mecamylamine produced a significant place aversion in Lewis, but not in Fischer 344 rats. These results suggest that mecamylamine-precipitated nicotine-withdrawal aversion is strongly regulated by genetic factors.

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.

Effects of diabetes on methamphetamine-induced place preference in mice

The effects of diabetes on methamphetamine-induced place preference in mice were examined. Methamphetamine caused a dose-dependent place preference in both diabetic and non-diabetic mice. Methamphetamine preferentially induced place preference in diabetic mice as compared to those in non-diabetic mice. Indeed, methamphetamine-induced place preference at a dose of 0.3 mg/kg in diabetic mice was similar to that at 3 mg/kg in non-diabetic mice. Furthermore, methamphetamine-induced place preference in both diabetic and non-diabetic mice was significantly antagonized by pretreatment with quinpirole, a dopamine D2/D3 receptor agonist. Methamphetamine-induced place preference was also antagonized by pretreatment with 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT), a selective dopamine D3 receptor agonist. On the other hand, 7-OH-DPAT produced significant place aversion in non-diabetic mice. 7-OH-DPAT produced neither place preference nor place aversion in diabetic mice. These results suggest that methamphetamine-induced place preference may be modulated by dopamine D3 receptors. Furthermore, increased dopamine neurotransmission associated with the down-regulation of presynaptic dopamine D3 receptor-mediated functions may account for the enhancement of methamphetamine's reinforcing effect in diabetic mice.

Dopamine receptor antagonists attenuate conditioned place preference following sexual behavior in female Syrian hamsters

We assessed the effects of the dopamine D2 receptor antagonists, sulpiride and raclopride, on conditioned place preference produced by sexual behavior in female Syrian hamsters. Female hamsters treated with sulpiride or raclopride showed high levels of sexual behavior (lordosis) that were equivalent to control females receiving vehicle injections. The degree of place preference conditioning for sulpiride-treated females was marginally reduced, whereas females treated with raclopride showed no evidence of conditioning. These results indicate that conditioned place preference is a useful means for probing the appetitive components of female sexual behavior, and that dopamine D2 receptors are involved in this appetitive process.

Discriminative stimulus properties of CGS 10746B: similarity to dopamine D1 receptor antagonists

CGS 10746B is an imidazole-derivative related to the atypical antipsychotic clozapine which produces a decrease in dopamine release without altering dopamine metabolism or occupying D2 receptors. Rats were trained on an appetitively-motivated, two-choice, operant task to discriminate 20.0 mg/kg CGS 10746B from its vehicle. CGS 10746B was highly discriminable, producing rapid acquisition of the discrimination, and its effects were dose-responsive allowing generation of an ED50 value of 6.16 mg/kg. Substitution tests were conducted with other typical and atypical antipsychotic compounds: haloperidol, chlorpromazine, clozapine and SCH 23390. Additional tests examined generalization from the CGS 10746B stimulus properties to the calcium channel blocker isradipine, as well as to the anticholinergics atropine, scopolamine and methylscopolamine, as well as to the serotonergic agonist DOI. Clozapine and SCH 23390 were the only substances to substitute for the CGS 10746B stimulus cue. Results are discussed in terms of potential D1 receptor selectivity of CGS 10746B.

Blockade of cocaine-induced conditioned place preference: relevance to cocaine abuse therapeutics

Conditioned place preference/aversion testing is a behavioral method believed capable of measuring the affective (positive, neutral or negative) properties of psychoactive drugs. Cocaine injections in rats reliably produces a positive place preference. Drugs that attenuate or block this effect of cocaine have obvious potential for developing treatments to address cocaine addiction as well as to add to the scientific understanding of the mechanism of cocaine's action at the cellular level. To date, six drugs have been reported to block the expression of a cocaine-induced conditioned place preference (CPP) and this review evidences the cocaine-induced CPP blockage by the two potent L-type calcium channel blockers, isradipine and nifedipine, the two serotonin-3 receptor antagonists, MDL72222 and ICS205-930, the delta opioid receptor selective antagonist naltrindole, and lastly, a mixed opioid agonist-antagonist buprenorphine. Additional evidence relating to the blockade of other cocaine behavioral effects by these putative blockers is addressed, where appropriate, from studies employing other procedures such as drug stimulus discrimination, self-administration, electrical brain stimulation and increases in locomotor activity. The significance of these findings is discussed in the context of their relevance to the development of treatment regimens to allow for cessation of cocaine abuse.