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Background: Muscarinic acetylcholine receptor 4 (M 4 ) modulates dopaminergic neurotransmission and is a target for novel treatments of schizophrenia, cognitive deficits, and addiction. Impulsive and compulsive behaviors are key traits of addiction, yet the importance of M 4 receptor signaling to these traits is poorly understood. We investigated impulsive action and compulsivity by measuring premature and perseverative responses in the five choice serial reaction time task (5CSRTT). Furthermore, we hypothesized that inter-trial interval (ITI) initiation settings affected training durations and test performances in these experiments., Methods: M 4 -/- and wildtype mice were trained and tested on two versions of the 5CSRTT with different ITI initiation settings. One setting, the head-in condition, allowed the ITI to start while the mouse's head remained in the reward receptacle (magazine). The other setting, the head-out condition, required the mouse to remove its head from the magazine to initiate the ITI., Results and Discussion: We did not observe differences in premature or perseverative responses in M 4 -/- mice in either condition, but found evidence of reward-related compulsive behavior in M 4 -/- mice. In the head-in condition, M 4 -/- mice were slower to acquire the 5CSRTT, had more omissions, and had longer correct response latencies than wildtype mice. In the head-out condition, genotypes did not differ in training, but M 4 -/- mice showed small decreases in accuracy. Our findings demonstrate that ITI initiation settings contribute to different training durations and tested behaviors in M 4 -/- mice, suggesting ITI initiation settings are an important consideration for the general use of the 5CSRTT., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The potential of abused drugs to induce addiction and compulsive drug-related behavior is associated with their ability to alter dopamine signaling. Dopamine plays a key role in reward signaling and it has been of great interest to investigate how various drugs of abuse alter reward-related behavior., Comparison With Existing Methods: In rodents, the rewarding effects of drugs have often been assessed in self-administration or place preference paradigms; both involving repeated drug exposure and weeks of training and testing., New Method: Our investigation describes a valid approach to assess the initial rewarding effects of cocaine in mice with a single exposure place preference (sePP) paradigm, avoiding repeated drug injections., Results: We present the sePP paradigm with a 3-day protocol to assess the initial rewarding effects of cocaine. Interestingly, only male mice exhibit sePP to cocaine. To assess subsequent drug-related behavior, the protocol was extended by 3days of extinction followed by reinstatement on day 10., Conclusion: The sePP paradigm provides a reliable and convenient approach to assess the initial rewarding effects of cocaine, circumventing the need for repeated drug injections. The sePP protocol allows further dissection of the mechanism and influence of initial cocaine exposure on subsequent drug-related behaviors by including extinction and reinstatement. The lack of sePP in female mice may reflect a biologically relevant sex difference in the initial subjective perception of cocaine-induced reward. This could relate to and explain why males and females have been reported to respond differently to cocaine and cocaine-associated cues., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Retigabine is a novel compound with anticonvulsant efficacy. Preclinical studies have indicated that the compound, like other anticonvulsants may also have antimanic efficacy. Bipolar disorder is characterized by episodes of depression and mania, which show a progressively faster recurrence and an increase in severity with time. Recurrence of episodes in bipolar disorders is suggested to reflect a process of sensitization. Repeated intermittent administration of amphetamine in rodents gives rise to a behavioral sensitization phenomena argued to have similarities to the sensitization found in humans. The aims were therefore to explore the predictive validity of the amphetamine sensitization model as a behavioral model of mania by testing the effect of a range of antimanic drugs and to evaluate the effect of retigabine on the sensitized amphetamine response. Furthermore, since withdrawal from prolonged use of amphetamine in humans can result in depression symptoms it was explored if a state of anhedonia could be assessed by testing saccharine preference before and during the withdrawal period of the model. The tested antimanic drugs (lithium, valproate, carbamazepine and lamotrigine) all attenuated the sensitized locomotor activity induced and with the exception of valproate the found effects seemed not to be due to sedation. Interestingly, retigabine also attenuated the induced locomotor activity with a lowest effective dose at 1.0mg/kg, whereas basal locomotor activity was only reduced at 8.0mg/kg, suggesting a genuine calming and antimanic-like efficacy of the compound. In addition, saccharine preference data suggest that withdrawal from the d-amphetamine pre-treatment regimen may induce depression-like behavior indicating that both manic and depression-like behavior is expressed in this mouse model.