Effects of amphetamine, methylphenidate, atomoxetine, and morphine in rats responding under an adjusting stop signal reaction time task

Methadone maintenance treatment and impulsivity: premature responding

INTRODUCTION

Previous research showed that methadone maintenance treatment (MMT) is linked to impulsivity, with higher impulsivity levels being associated with for example, increased drug use. One aspect of impulsivity, most commonly studied in rodent research, is premature responding, the failure to wait for a starting signal. Premature responding is of high translational significance since it predicts the development of addiction-like behaviors in rodents.

METHODS

We assessed 45 MMT patients and 46 demographically matched (age, sex, education, and handedness) healthy volunteers (HVs) on premature responding alongside action and inhibition of instructed and intentional trials using the Intentional Hand Task (IHT).

RESULTS

The results showed markedly enhanced premature responses in the MMT vs. the HV group, which correlated positively with methadone dosage in the MMT patients. Throughout the task, MMT patients were faster across all trial parts and less accurate in response to instructed trials compared to HVs.

CONCLUSIONS

The increase in premature motor reactions during variable waiting periods alongside increased motion speed and lower accuracy might reflect a specific motor inhibition deficit in MMT, a subcomponent of impulsivity not previously assessed in MMT. Incorporating an experimentally defined measure of impulsivity, such as premature responding, into existing test batteries used by clinicians might enable more tailored treatments addressing the increased impulsivity levels and associated dysfunctional behaviors in MMT.

Effectiveness of Response Inhibition Training and Its Long-Term Effects in Healthy Adults: A Systematic Review and Meta-Analysis

Objective

This study aims to evaluate the effectiveness and long-term effects of response inhibition training as a therapeutic approach in healthy adults.

Methods

The PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang, and China Science and Technology Journal Database (VIP) were searched for studies. Data on the improvement of Cognitive function and its long-term effect were extracted by two authors independently. The pooled data were meta-analyzed using a random-effects model, and the quality of each eligible study was assessed by The Cochrane Collaboration’s tool.

Results

Nine articles were included. 1 of the articles included 2 trials, so 10 eligible trials (response inhibition training group vs. control group) were identified. A total of 490 patients were included. Response inhibition training has beneficial effects on improving cognitive function in healthy adults compared to control treatment (SMD, −0.93; 95% CI, −1.56 to −0.30; Z = 2.88, P = 0.004), the subgroup analysis results showed that either GNG training alone (SMD, −2.27; 95% CI, −3.33 to −1.21; Z = 4.18, P < 0.0001) or the combination of both SST and GNG significantly improved cognitive function in healthy adults (SMD, −0.94; 95% CI, −1.33 to −0.56; Z = 4.80, P < 0.0001), whereas SST training alone did not have such an effect (SMD, −0.15; 95% CI, −0.76 to 0.47; Z = 0.47, P = 0.64). But its long-term effects are not significant (SMD, −0.29; 95% CI, −0.68 to 0.10; Z = 1.45, P = 0.15). The subgroup analysis results showed that neither GNG training alone (SMD, −0.25; 95% CI, −0.75 to 0.24; Z = 0.99, P = 0.32) nor SST training alone (SMD, 0.03; 95% CI, −0.42 to 0.48; Z = 0.14, P = 0.89) could improve the cognitive function of healthy adults in the long term. In contrast, the combination of both training (SMD, −0.95; 95% CI, −1.46 to −0.45; Z = 3.68, P = 0.0002) can have long-term effects on the improvement of cognitive function in healthy adults.

Conclusion

The findings of our study indicate that response inhibition training can improve the cognitive function of healthy adults and that more RCTs need to be conducted to validate their usefulness in clinical cases.

The Effects of Drug Treatments for ADHD in Measures of Cognitive Performance

Based on core symptoms of inattention and deficient impulse control, and the identification of effective pharmacotherapies such as amphetamine (AMP; Adderall^®), methylphenidate (MPH; Ritalin^®), and atomoxetine (ATX; Strattera^®), ADHD is a clinical condition which provides opportunity for translational research. Neuropsychological tests such as the 5-Choice and Continuous Performance Tasks, which measure aspects of attention and impulse control in animals and humans, provide scope for both forward (animal to human) and reverse (human to animal) translation. Rodent studies support pro-attentive effects of AMP and MPH and effectiveness in controlling some forms of impulsive behavior. In contrast, any pro-attentive effects of ATX appear to be less consistent, the most reliable effects of ATX are recorded in tests of impulsivity. These differences may account for AMP and MPH being recognized as first-line treatments for ADHD with a higher efficacy relative to ATX. DSM-5 classifies three "presentations" of ADHD: predominantly inattentive type (ADHD-I), predominantly hyperactive/impulsive type (ADHD-HI), or combined (ADHD-C). Presently, it is unclear whether AMP, MPH, or ATX has differential levels of efficacy across these presentation types. Nonetheless, these studies encourage confidence for the forward translation of NCEs in efforts to identify newer pharmacotherapies for ADHD.

Examining the effects of psychoactive drugs on complex behavioral processes in laboratory animals

Behavioral pharmacology has been aided significantly by the development of innovative cognitive tasks designed to examine complex behavioral processes in laboratory animals. Performance outcomes under these conditions have provided key metrics of drug action which serve to supplement traditional in vivo assays of physiologic and behavioral effects of psychoactive drugs. This chapter provides a primer of cognitive tasks designed to assay different aspects of complex behavior, including learning, cognitive flexibility, memory, attention, motivation, and impulsivity. Both capstone studies and recent publications are highlighted throughout to illustrate task value for two distinct but often interconnected translational strategies. First, task performance in laboratory animals can be utilized to elucidate how drugs of abuse affect complex behavioral processes. Here, the expectation is that adverse effects on such processes will have predictive relevance to consequences that will be experienced by humans. Second, these same task outcomes can be used to evaluate candidate therapeutics. In this case, the extent to which drug doses with medicinal value perturb task performance can contribute critical information for a more complete safety profile appraisal and advance the process of medications development. Methodological and theoretical considerations are discussed and include an emphasis on determining selectivity in drug action on complex behavioral processes.

Contrasting effects of d-amphetamine and atomoxetine on measures of impulsive action and choice

Amphetamine (AMP) and atomoxetine (ATX) represent two of the most widely studied drug treatments used in the investigation of impulsive behaviour. While both drugs have relatively well defined effects in tests designed to investigate impulsive action (e.g. 5-choice task; 5-CSRTT), the effects of both drugs in tests of impulsive choice (e.g. delay discounting) are less consistent. In the present study both AMP and ATX were tested in a rodent gambling task (rGT) and delay discounting in rats separately trained to either an ascending or descending delay schedule. Effects of both drugs were compared to measures of impulsive action (premature (PREM) responses) and perseverative (PSV) responses measured in the 5-choice and rGT tasks. Consistent with previous studies, AMP (0.1-1 mg/kg) increased both PREM and PSV responses, and ATX (0.5-2 mg/kg) reduced both measures in the 5-choice and rGT tasks. At equivalent doses ATX had no reliable effect on choice behaviour in either the rGT or delay discounting suggesting a null effect of this drug on impulsive choice and risky decision making. The effects of AMP were more complex, with a subtle shift in preference to a low risk (P1) choice in the rGT, and an effect on discounting that was unrelated to reinforcer value, but instead dependent on delay sequence and baseline choice preference. One aspect to these outcomes is to highlight the importance of multiple methodological factors when assessing drug effects on complex behaviours such as impulsive choice, and question what are the most appropriate test conditions under which to examine these drugs on discounting.