7 
The authors provide initial documentation that juvenile rats emit short, high-frequency ultrasonic vocalizations (high USVs, ?55 kHz) during rough-and-tumble play. In an observational study, they further observe that these vocalizations both correlate with and predict appetitive components of the play behavioral repertoire. Additional experiments characterized eliciting conditions for high USVs. Without prior play exposure, rats […]
6 
Juvenile social interactions have been shown to influence the dendritic complexity of neurons in the prefrontal cortex (PFC). In particular, social play induces pruning of the cells in the medial prefrontal cortex (mPFC), whereas interacting with multiple partners, whether those interactions involve play or not, increases the complexity of cells in the orbital frontal cortex […]
9 
1st paragraph of this short essay: In the beginning was the word…but was the word funny? Research suggests that the capacity for human laughter preceded the capacity for speech during evolution of the brain. Indeed, neural circuits for laughter exist in very ancient regions of the brain (1), and ancestral forms of play and laughter existed in other animals […]
9 When rats engage in playful interactions, they emit appetitive 50-kHz ultrasonic vocalizations (USVs). We investigated the role of 50-kHz USVs in the playful behavior of both juvenile and adult rats. A cohort of juvenile rats was surgically devocalized and allowed to interact with either devocalized or intact partners as juveniles and again as adults. A […]
7 
play fighting is a highly rewarding behavior that helps individuals to develop social skills. Early-life stress has been shown to alter play fighting in rats and hamsters as well as to increase aggressive behaviors at adulthood. However, it is not known whether individual differences in stress-induced play fighting are related to differential developmental trajectories towards […]
4 
Deficits in social approach behavior, rough-and-tumble play, and speech abnormalities are core features of autism that can be modeled in laboratory rats. Human twin studies show that autism has a strong genetic component, and a recent review has identified 99 genes that are dysregulated in human autism. Bioinformatic analysis of these 99 genes identified the […]
5 Play is an important part of normal childhood development and seen in many mammals, including rats. To better understand the interplay between genotype and postnatal experiences, the effects of neonatal handling on play were assessed in Lewis (LEW) and Fischer 344 (F344) rats. Handled litters experienced brief periods of separation during the first two postnatal […]
7 Rats selectively bred for susceptibility to amygdala kindling (FAST) have been shown to retain neural and behavioral features of the juvenile phase into adulthood. In contrast, rats selectively bred for resistance to amygdala kindling (SLOW) are neurobehaviorally more typically adult. The development of play fighting in male and female rats of both selected lines was […]
4 
Summary Social grooming and rough-and-tumble play, along with caressing and hand-shaking, have something important in common, touching. Physical contact with another can be an essential ingredient of social communication – gentle touching can place the other animal at ease, whereas rough contact can do the opposite. Although the underlying neurobiology is still to be fully […]
8 
This chapter examines play and fighting behavior in rats. It begins with a discussion of serious fighting of adults, which is then contrasted with the playful fighting of juveniles. It shows that serious and playful fighting are distinct behaviors in rats, with play derived from sex, not aggression. Rats have modified the sexual content of […]
7 
Potentiating social, cognitive, and sensorimotor stimulations the Environmental Enrichment (EE) increases levels of novelty and complexity experienced by individuals. Growing evidence demonstrates that parental EE experience, even occurring in the pre-reproductive phase, affects behavioral and neural developmental trajectories of the offspring. To discover how the accumulation of early maternal complex experiences may inform and shape […]
6 
Catalepsy, a symptom of Parkinson’s disease and related disorders can be produced in rats and other laboratory animals by the blockade of nigrostriatal dopamine using dopaminergic antagonists such as haloperidol. When haloperidol-induced cataleptic rats are placed facing downward on an inclined plane, they will brace against the resulting downward force by pushing backwards, and if […]
4 
Rats protect food by dodging horizontally away from a conspecific. Females and males use different movement and stepping patterns to execute a dodge. An unresolved question is whether exposure to ovarian steroids in females is necessary for the development of the female-typical pattern. Females ovariectomized neonatally and prior to puberty use a combination of male […]
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In rats, hedonic ultrasonic vocalizations (USVs) is a validated model of positive affect and is best elicited by rough-and-tumble play. Here we report that modulation of GluN2B-containing NMDA receptors (NMDAR) in the medial prefrontal cortex (MPFC) is involved in positive emotional learning. Rough and tumble play increased both GluN1 and GluN2B NMDAR subunit mRNA and […]
6 
Juvenile social play contributes to the development of adult social and emotional skills in humans and non-human animals, and is therefore a useful endpoint to study the effects of endocrine disrupters on behavior in animal models. Ethinylestradiol (EE2) is a widely produced, powerful synthetic estrogen that is widespread in the environment mainly because is a […]
7 
Rat 22-kHz ultrasonic vocalizations (USVs) are exhibited in response to a wide variety of stimuli. Recently, we have shown that, depending on the internal state of the animal, a given stimulus can either trigger aversive 22-kHz USVs or hedonic 50-kHz USVs. Notably, preexposure to reward/stress shifts this response of rats; we can selectively breed in […]
6 
play fighting is most commonly associated with juvenile animals, but in some species, including rats, it can continue into adulthood. Post-pubertal engagement in play fighting is often rougher and has an increased chance of escalation to aggression, making the use of play signals to regulate the encounter more critical. During play, both juvenile and adult […]
8
Ultrasonic vocalizations of around 50 kHz are emitted extensively during the play fighting of rats, reflecting a positive affective state. Some of these calls are associated with facilitating playóat an emotional level they appear to promote the playful mood of both the emitter and the recipient and at a tactical level they appear to coordinate […]
8 
Studies on laboratory rats (Rattus norvegicus) have revealed that experience with social play in the juvenile period is important for the development of improved social skills, an improvement that appears to be mediated by the prefrontal cortex. But there is much variation in both the frequency with which play occurs and in the complexity of […]
4
Evidence for the hypothesis that brain-opioids mediate social affect and social attachments is summarized. Opiates and opioids are very effective in reducing social separation-induced distress vocalizations (DVs), in puppies, young guinea pigs and chicks, while opiate antagonists can increase DVs. In studies of specific social behaviors in rodents, morphine (at doses 1 mg/kg and below) […]
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