Nicotine-motivated behavior in Caenorhabditis elegans requires the nicotinic acetylcholine receptor subunits acr-5 and acr-15.

Signaling at nicotinic acetylcholine receptors in Caenorhabditis elegans controls many behaviors, including egg-laying and locomotor activity. Here, we show that C. elegans approaches a point source of nicotine in a time-, concentration- and age-dependent manner.

Research of the Holiday kind: Tabulating Ingestion of Mocha Solution (TIMS): a longitudinal prospective cohort study.

The annual "Roll Up the Rim to Win" contest at Tim Hortons restaurants provides customers the opportunity to win prizes. This study investigated win ratios, prize types and patterns of coffee consumption.

Adenosine A1 and A2A receptors are not upstream of caffeine's dopamine D2 receptor-dependent aversive effects and dopamine-independent rewarding effects.

Caffeine is widely consumed throughout the world, but little is known about the mechanisms underlying its rewarding and aversive properties. We show that pharmacological antagonism of dopamine not only blocks conditioned place aversion to caffeine, but also reveals dopamine blockade-induced conditioned place preferences. These aversive effects are mediated by the dopamine D(2) receptor, as knockout mice showed conditioned place preferences in response to doses of caffeine that C57Bl/6 mice found aversive.

Insulin signaling plays a dual role in Caenorhabditis elegans memory acquisition and memory retrieval.

Insulin signaling plays a prominent role in regulation of dauer formation and longevity in Caenorhabditis elegans. Here, we show that insulin signaling also is required in benzaldehyde-starvation associative plasticity, in which worms pre-exposed to the odor attractant benzaldehyde in the absence of food subsequently demonstrate a conditioned aversion response toward the odorant. Animals with mutations in insulin-related 1 (ins-1), abnormal dauer formation 2 (daf-2), and aging alteration 1 (age-1), which encode the homolog of human insulin, insulin/IGF-1 receptor, and PIP3 kinase, respectively, demonstrated significant deficits in benzaldehyde-starvation associative plasticity.

A diacetyl-induced quiescence in young Caenorhabditis elegans.

Many organisms enter quiescence in response to adverse environmental factors. Here, we show that L1 stage C. elegans entered a quiescent state after 3hours exposure to diacetyl in which movement and growth stopped for hours to days after odorant removal.

Dopaminergic signaling mediates the motivational response underlying the opponent process to chronic but not acute nicotine.

The mesolimbic dopamine (DA) system is implicated in the processing of the positive reinforcing effect of all drugs of abuse, including nicotine. It has been suggested that the dopaminergic system is also involved in the aversive motivational response to drug withdrawal, particularly for opiates, however, the role for dopaminergic signaling in the processing of the negative motivational properties of nicotine withdrawal is largely unknown. We hypothesized that signaling at dopaminergic receptors mediates chronic nicotine withdrawal aversions and that dopaminergic signaling would differentially mediate acute vs dependent nicotine motivation.

Social dominance rank influences wheel running behavior in mice.

Dominance hierarchies within social groups determine resource distribution. Resources, such as food and access to mating partners, can act as reinforcers. The present study examined the effect of social rank on access to wheel running-a reinforcing behavior performed by laboratory animals.

Reinforcement of wheel running in BALB/c mice: role of motor activity and endogenous opioids.

The authors investigated the effect of the opioid antagonist naloxone on wheel-running behavior in Balb/c mice. Naloxone delayed the acquisition of wheel-running behavior, but did not reduce the expression of this behavior once acquired. Delayed acquisition was not likely a result of reduced locomotor activity, as naloxone-treated mice did not exhibit reduced wheel running after the behavior was acquired, and they performed normally on the rotarod test.

Rewarding and aversive effects of nicotine are segregated within the nucleus accumbens.

Forebrain dopamine plays a critical role in motivated behavior. According to the classic view, mesolimbic dopamine selectively guides behavior motivated by positive reinforcers. However, this has been challenged in favor of a wider role encompassing aversively motivated behavior.

Evidence for multiple sites within rat ventral striatum mediating cocaine-conditioned place preference and locomotor activation.

Considerable evidence suggests that psychostimulants can exert rewarding and locomotor-stimulating effects via increased dopamine transmission in the ventral striatum. However, the relative contributions of ventral striatal subregions to each of these effects have been little investigated. In the present study, we examined the contribution of different ventral striatal sites to the rewarding and locomotor-activating effects of cocaine.

6-Hydroxydopamine lesions of nucleus accumbens core abolish amphetamine-induced conditioned activity.

Environmental cues associated with drug experiences appear to play a critical role in drug dependence. We have previously reported that dopamine-depleting lesions of the nucleus accumbens medial shell inhibit amphetamine-conditioned place preference. Here, we examined the effects of analogous lesions on amphetamine-conditioned locomotor activity.

Segregation of amphetamine reward and locomotor stimulation between nucleus accumbens medial shell and core.

Convergent evidence suggests that amphetamine (AMPH) exerts its rewarding and locomotor stimulating effects via release of dopamine in the nucleus accumbens. However, there is no consensus as to the relative contributions of core and medial shell subregions to these effects. Moreover, the literature is based primarily on intracranial administration, which cannot fully mimic the drug distribution achieved by systemic administration.