Effect of Scopolamine on Mice Motor Activity, Lick Behavior and Reversal Learning in the IntelliCage

Pro-cognitive effects of dual tacrine derivatives acting as cholinesterase inhibitors and NMDA receptor antagonists

Therapeutic options for Alzheimer's disease are limited. Dual compounds targeting two pathways concurrently may enable enhanced effect. The study focuses on tacrine derivatives inhibiting acetylcholinesterase (AChE) and simultaneously N-methyl-D-aspartate (NMDA) receptors. Compounds with balanced inhibitory potencies for the target proteins (K1578 and K1599) or increased potency for AChE (K1592 and K1594) were studied to identify the most promising pro-cognitive compound. Their effects were studied in cholinergic (scopolamine-induced) and glutamatergic (MK-801-induced) rat models of cognitive deficits in the Morris water maze. Moreover, the impacts on locomotion in the open field and AChE activity in relevant brain structures were investigated. The effect of the most promising compound on NMDA receptors was explored by in vitro electrophysiology. The cholinergic antagonist scopolamine induced a deficit in memory acquisition, however, it was unaffected by the compounds, and a deficit in reversal learning that was alleviated by K1578 and K1599. K1578 and K1599 significantly inhibited AChE in the striatum, potentially explaining the behavioral observations. The glutamatergic antagonist dizocilpine (MK-801) induced a deficit in memory acquisition, which was alleviated by K1599. K1599 also mitigated the MK-801-induced hyperlocomotion in the open field. In vitro patch-clamp corroborated the K1599-associated NMDA receptor inhibitory effect. K1599 emerged as the most promising compound, demonstrating pro-cognitive efficacy in both models, consistent with intended dual effect. We conclude that tacrine has the potential for development of derivatives with dual in vivo effects. Our findings contributed to the elucidation of the structural and functional properties of tacrine derivatives associated with optimal in vivo pro-cognitive efficacy.

Whisker trimming during infanthood modifies the development of spike-wave discharges and behavioral sequences in IntelliCage impulsivity paradigm in adult WAG/Rij rats

Whisker system in rats undergoes rapid development during the first postnatal weeks. Neonatal whisker trimming increases excitability in the somatosensory cortex and affects exploratory behavior at adult ages. WAG/Rij rats are genetically predisposed to develop absence seizures in adulthood, and whisker trimming during three postnatal weeks aggravates epileptic activity in these rats. It is assumed that behavioral performance in adult WAG/Rij rats is influenced (1) by absence epilepsy and (2) by whisker trimming during the short period around the onset of active whisker movements, PN9-16. We examined the effect of whisker trimming in WAG/Rij rats during PN9-16 on spike-wave discharges (SWD, EEG hallmark of absence epilepsy). We found that 77% of WAG/Rij rats showed pronounced SWD (epileptic phenotype), and the rest did not (non-epileptic phenotype). At the age of 5 m, epileptic trimmed rats showed more SWD than epileptic control rats. Age-related increase of SWD was found only in the control group, suggesting that whisker trimming during PN9-16 led to an earlier maturation of SWD. Goal-directed behavior was examined in all rats at the age of 4-4.5 m using IntelliCage impulsivity paradigm. In order to optimize the analysis of behavioral data, we combined several Python packages into a single processing pipeline. Early life whisker trimming altered behavioral sequences and strategy of exploration in adulthood, suggesting reduced whisker sensitivity in the trimmed rats. Epileptic WAG/Rij rats at 4-4.5 months showed only a slight learning impairment during later stages of IntelliCage impulsivity paradigm, which may be associated with the early stage of development of SWD.

Effects of chronic tramadol administration on cognitive flexibility in mice

RATIONALE

Tramadol is widely used for pain relief especially in seniors. However, long-term use of tramadol has serious adverse effects, including cognitive impairment. Besides its memory effects, already demonstrated in animals, a recent clinical report suggests that tramadol could also affect executive function in seniors. Several studies have hypothesized that the anti-muscarinic properties of tramadol could be responsible for the deleterious effects of tramadol on cognition.

OBJECTIVES

We aimed at investigating the effects of chronic administration of tramadol on cognitive flexibility in adult male mice, as assessed by a visual discrimination reversal task using a touchscreen device. The effects of tramadol were further compared to those of scopolamine, a reference muscarinic antagonist.

RESULTS

We found that, during the early phase of the reversal task, when cognitive flexibility is most in demand, both tramadol-treated mice (20 mg/kg, s.c., twice a day) and scopolamine-treated mice (0.5 mg/kg, s.c., twice a day) needed more correction trials and showed a higher perseveration index than saline-treated mice. Therefore, tramadol affects cognitive flexibility, and its anticholinergic properties could be at least partly involved in these deficits.

CONCLUSIONS

In view of these deleterious cognitive effects of tramadol, physicians should be cautious when prescribing this analgesic, especially in seniors who are more vulnerable to adverse drug events and in which alternative prescription should be preferred whenever possible.

Kamikihito Enhances Cognitive Functions and Reward-Related Behaviors of Aged C57BL/6J Mice in an Automated Behavioral Assay System

The cognitive and psychological domains of frailty in the elderly have drawn increasing attention given the aging of society. However, therapeutics to treat minor deficits in cognition and mental state in the elderly remain an unmet need. Kamikihito (KKT), a traditional Japanese Kampo medicine indicated for neuroses, anxiety, and insomnia, is effective for treating cognitive dysfunction and depressive-like behaviors in animal models, suggesting that it may have therapeutic potential for treating cognitive and/or mental frailty. In this study, we first validated the known anxiolytic effects of KKT in a conventional maze test. We then introduced an automated behavioral assay system, IntelliCage, to evaluate the therapeutic potential of KKT for age-related and diverse central functions by performing sequential behavioral tasks in young and aged mice to assess basal activities, cognitive functions, perseveration, and hedonic-related behaviors. Although young mice treated with KKT did not exhibit changes in diurnal variation, KKT-administered aged mice exhibited an accelerated decline in voluntary activity during the early part of the light period, implying that KKT may promote sleep onset in aged mice. Neither place learning acquisition for gaining rewards nor subsequent behavioral flexibility performance was altered by KKT in the young group, whereas the aged KKT group exhibited significantly enhanced performance in both phases of learning relative to age-matched controls. Conversely, perseverative nose-pokes (NPs) to gain rewards observed during place learning, indicative of compulsivity, were attenuated by KKT in both age groups. Regarding hedonic processing, aged mice exhibited a decreased preference for sweet solutions compared to young mice, which was effectively reversed by KKT treatment. Furthermore, KKT elevated high-effort choices for high-value reward in an effort-based decision-making paradigm in both age groups, implying augmentation of motivational behaviors by KKT. Collectively, KKT exerted various beneficial effects in cognitive and emotional domains, several of which were more evident in aged mice than in young mice, suggesting the potential of KKT for treating cognitive and mental frailty.

IntelliCage as a tool for measuring mouse behavior - 20 years perspective

Since the 1980s, we have witnessed the rapid development of genetically modified mouse models of human diseases. A large number of transgenic and knockout mice have been utilized in basic and applied research, including models of neurodegenerative and neuropsychiatric disorders. To assess the biological function of mutated genes, modern techniques are critical to detect changes in behavioral phenotypes. We review the IntelliCage, a high-throughput system that is used for behavioral screening and detailed analyses of complex behaviors in mice. The IntelliCage was introduced almost two decades ago and has been used in over 150 studies to assess both spontaneous and cognitive behaviors. We present a critical analysis of experimental data that have been generated using this device.

Comparison of conventional and rapid-acting antidepressants in a rodent probabilistic reversal learning task

Deficits in reward processing are a central feature of major depressive disorder with patients exhibiting decreased reward learning and altered feedback sensitivity in probabilistic reversal learning tasks. Methods to quantify probabilistic learning in both rodents and humans have been developed, providing translational paradigms for depression research. We have utilised a probabilistic reversal learning task to investigate potential differences between conventional and rapid-acting antidepressants on reward learning and feedback sensitivity. We trained 12 rats in a touchscreen probabilistic reversal learning task before investigating the effect of acute administration of citalopram, venlafaxine, reboxetine, ketamine or scopolamine. Data were also analysed using a Q-learning reinforcement learning model to understand the effects of antidepressant treatment on underlying reward processing parameters. Citalopram administration decreased trials taken to learn the first rule and increased win-stay probability. Reboxetine decreased win-stay behaviour while also decreasing the number of rule changes animals performed in a session. Venlafaxine had no effect. Ketamine and scopolamine both decreased win-stay probability, number of rule changes performed and motivation in the task. Insights from the reinforcement learning model suggested that reboxetine led animals to choose a less optimal strategy, while ketamine decreased the model-free learning rate. These results suggest that reward learning and feedback sensitivity are not differentially modulated by conventional and rapid-acting antidepressant treatment in the probabilistic reversal learning task.