Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.

Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade.

Glutamate receptor function in learning and memory

https://boerenlandvogels.nl/sites/default/files/Dwyer%20et%20al_%20Pharmacol%20Ther_2009.pdf

The Dynamic Effects of Nicotine on the Developing Brain

BACKGROUND AND OBJECTIVE: Currently, the US Food and Drug Administration does not regulate electronic cigarette (e-cigarette) marketing unless it is advertised as a smoking cessation aid. To date, the extent to which youth and young adults are exposed to e-cigarette television advertisements is unknown. The objective of this study was to analyze trends in youth and young adult exposure to e-cigarette television advertisements in the United States. METHODS: Nielsen data on television household audiences’ exposure to e-cigarette advertising across US markets were examined by calendar quarter, year, and sponsor. RESULTS: Youth exposure to television e-cigarette advertisements, measured by target rating points, increased 256% from 2011 to 2013. Young adult exposure increased 321% over the same period. More than 76% of all youth e-cigarette advertising exposure occurred on cable networks and was driven primarily by an advertising campaign for 1 e-cigarette brand. CONCLUSIONS: E-cigarette companies currently advertise their products to a broad audience that includes 24 million youth. The dramatic increase in youth and young adult television exposure between 2011 and 2013 was driven primarily by a large advertising campaign on national cable networks. In the absence of evidence-based public health messaging, the current e-cigarette television advertising may be promoting beliefs and behaviors that pose harm to the public health. If current trends in e-cigarette television advertising continue, awareness and use of e-cigarettes are likely to increase among youth and young adults.

https://pediatrics.aappublications.org/content/pediatrics/134/1/e29.full.pdf

Exposure to Electronic Cigarette Television Advertisements Among Youth and Young Adults

The Gateway Hypothesis describes how tobacco or alcohol use precedes marijuana and other illicit drug use. We review the epidemiological data, explore the underlying molecular mechanisms in mice and discuss the societal implications of the hypothesis, including the use of e-cigarettes by young people.

Conclusion
Our mouse model identifies biological processes underlying the hypothesis, showing that nicotine is a gateway drug that exerts a priming effect on cocaine through increased global acetylation in the striatum.

The Gateway Hypothesis of substance abuse: developmental, biological and societal perspectives.

Long-term, low-level adolescent nicotine exposure produces dose-dependent changes in cocaine sensitivity and reward in adult mice.

In 3 experiments, rats and humans learned serial patterns composed of 24, 30, or 36 items. Patterns had a 2-, 3-, or 4-level hierarchical rule structure. In Experiments 1 and 2, patterns had either perfect hierarchical structure or 2 modified chunks that violated hierarchical structure, thus producing linear structure (i.e., nonhierarchical structure). For both rats and humans, pattern structure predicted pattern learning difficulty and also the nature and relative frequency of errors. Both treated chunks that were inconsistent with hierarchical structure as violation chunks, that is, they made errors that reflected their "tendency to regularize the perception of an irregular pattern" (F. Restle & B. L. Burnside, 1972). The results support the view that rats can abstract and encode a representation of multilevel hierarchical structure in serial patterns in much the same way as humans do in analogous tasks.

Coding of hierarchical versus linear pattern structure in rats and humans.

Rats learned serial patterns composed of either "run" chunks (e.g., 123 234 ...) or "trill" chunks (e.g., 121 232 ...). For each type of pattern, 1 group of rats encountered an element at the end of the pattern that violated the run or trill structure. In both run and trill patterns, violations were unusually difficult for rats to learn, whereas corresponding elements in "perfect" patterns that did not violate pattern structure were easy. Additionally, rats' errors on violation elements conformed to the structure of the patterns in which they were embedded. Thus, rats were sensitive to the run or trill organization of their patterns and mastered the rules governing the pattern before learning "exceptions to the rule."

Sensitivity to violations of "run" and "trill" structures in rat serial-pattern learning.

In the present study investigating the effects of adolescent nicotine exposure on adult serial pattern learning, adolescent rats received daily i.p. injections of either 1.0 mg/kg nicotine or saline for 5 days per week for 5 weeks beginning on postnatal day 25 (P25), then were allowed 35 days drug free. Rats then began training on P95 as adults on a 24-element serial pattern composed of eight 3-element chunks. Adolescent exposure to 1.0 mg/kg nicotine produced persistent retardation of learning for the first element of each 3-element chunk of the pattern, that is, for chunk boundary elements, and transient retardation of learning for elements 2 and 3 of each chunk of the pattern, that is, for the within-chunk elements. Deficits at chunk boundaries were interpreted as deficits of phrasing cue discrimination learning whereas deficits for learning responses for elements within-chunks (elements 2 and 3 of chunks) were interpreted as deficits of rule learning. These results indicate that the effects of adolescent nicotine exposure on adult learning and cognitive capacity deserve further scrutiny.

Adolescent exposure to nicotine impairs adult serial pattern learning in rats

Three experiments investigated the role of NMDA receptor dependent systems in sequential learning and memory. Rats tracked serial patterns after systemic administration of MK-801, an NMDA receptor antagonist that blocks plasticity in the hippocampus and other structures. Experiments 1 and 2 sought to describe the effects of MK-801 on acquisition and retention of serial patterns. Patterns were 24 elements long and highly organized, with some groups receiving a “violation” element that did not fit the organization of the rest of the pattern. Experiment 3 evaluated MK-801’s effects on the integration of new information that was either consistent or inconsistent with a previously learned pattern structure. The results of these experiments indicated that MK-801 interfered with serial pattern learning and, to a lesser degree, retention. Learning about structure was relatively spared, whereas learning about interruptions or violations of pattern structure was impaired. The latter differential effects are consistent with the contention in earlier literature that serial pattern learning is subserved by at least two learning/memory systems.

/pdf/differential-impairments-of-rat-serial-pattern-learning-and-2cdpo6kg5t.pdf

James D. Rowan

Papers

Long-term, low-level adolescent nicotine exposure produces dose-dependent changes in cocaine sensitivity and reward in adult mice.

Coding of hierarchical versus linear pattern structure in rats and humans.

Sensitivity to violations of "run" and "trill" structures in rat serial-pattern learning.

Adolescent exposure to nicotine impairs adult serial pattern learning in rats

Differential impairments of rat serial pattern learning and retention induced by MK-801, an NMDA receptor antagonist