Novel Antimuscarinic Antidepressant-like Compounds with Reduced Effects on Cognition

Chronic ecologically relevant stress effects on reverse-translated touchscreen assays of reward responsivity and attentional processes in male rats: Implications for depression

Stagnation in the development of novel therapeutic strategies for treatment-resistant depression has encouraged continued interest in improving preclinical methods. One tactic prioritizes the reverse translation of behavioral tasks developed to objectively quantify depressive phenotypes in patient populations for their use in laboratory animals via touchscreen technology. After cross-species concordance in task outcomes under healthy conditions is confirmed, construct validity can be further enhanced by identifying environmental stressors that reliably produce deficits in task performance that resemble those in depressive participants. The present studies characterized in male rats the ability of two chronic ecologically relevant stressors, inescapable ice water or isolated restraint, to produce depressive-like behavioral phenotypes in the Probabilistic Reward Task (PRT) and Psychomotor Vigilance Task (PVT). These tasks previously have been reverse-translated using touchscreen technology for rodents and nonhuman primates to objectively quantify, respectively, reward responsivity (anhedonia) and attentional processes (impaired cognitive function), each of which are core features of major depressive disorder. In the PRT, both inescapable ice water and isolated restraint produced persistent anhedonic phenotypes compared to non-stressed control performance (i.e., significantly blunted response bias for the richly rewarded stimulus). In the PVT, both chronic stressors impaired attentional processing, revealed by increases in titrated reaction times; however, these deficits largely subsided by the end of the chronic condition. Taken together, these findings confirm the ability of reverse-translated touchscreen tasks to effectively generate behavioral phenotypes that exhibit expected deficits in performance outcomes following exposure to chronic ecologically relevant stress. In turn, this approach is well positioned to appraise the ability of candidate therapeutics to attenuate or reverse such behavioral deficits and, thereby, contribute to preclinical medications development for treatment-resistant depression.

Open science and data sharing in cognitive neuroscience with MouseBytes and MouseBytes

Open access to rodent cognitive data has lagged behind the rapid generation of large open-access datasets in other areas of neuroscience, such as neuroimaging and genomics. One contributing factor has been the absence of uniform standardization in experiments and data output, an issue that has particularly plagued studies in animal models. Touchscreen-automated cognitive testing of animal models allows standardized outputs that are compatible with open-access sharing. Touchscreen datasets can be combined with different neuro-technologies such as fiber photometry, miniscopes, optogenetics, and MRI to evaluate the relationship between neural activity and behavior. Here we describe a platform that allows deposition of these data into an open-access repository. This platform, called MouseBytes, is a web-based repository that enables researchers to store, share, visualize, and analyze cognitive data. Here we present the architecture, structure, and the essential infrastructure behind MouseBytes. In addition, we describe MouseBytes+, a database that allows data from complementary neuro-technologies such as imaging and photometry to be easily integrated with behavioral data in MouseBytes to support multi-modal behavioral analysis.

Drug Design Targeting the Muscarinic Receptors and the Implications in Central Nervous System Disorders

There is substantial evidence that cholinergic system function impairment plays a significant role in many central nervous system (CNS) disorders. During the past three decades, muscarinic receptors (mAChRs) have been implicated in various pathologies and have been prominent targets of drug-design efforts. However, due to the high sequence homology of the orthosteric binding site, many drug candidates resulted in limited clinical success. Although several advances in treating peripheral pathologies have been achieved, targeting CNS pathologies remains challenging for researchers. Nevertheless, significant progress has been made in recent years to develop functionally selective orthosteric and allosteric ligands targeting the mAChRs with limited side effect profiles. This review highlights past efforts and focuses on recent advances in drug design targeting these receptors for Alzheimer’s disease (AD), schizophrenia (SZ), and depression.

Nicotinic aspects of the discriminative stimulus effects of arecoline

Despite the evidence that the muscarinic agonist arecoline is a drug of abuse throughout Southeast Asia, its stimulus characteristics have not been well studied. The goal of this work was to understand more about the mediation of discriminative stimulus effects of arecoline. Arecoline (1.0 mg/kg s.c.) was trained as a discriminative stimulus in a group of eight rats. The ability of various cholinergic agonists and antagonists to mimic or antagonize the discriminative stimulus effects of arecoline and to modify its rate-suppressing effects was evaluated. A muscarinic antagonist, but neither of two nicotinic antagonists, was able to modify the discriminative stimulus effects of arecoline, suggesting a predominant muscarinic basis of arecoline's discriminative stimulus effects in this assay. However, both nicotine itself and two nicotine agonists with selective affinity for the α4β2* receptor (ispronicline and metanicotine) produced full arecoline-like discriminative stimulus effects in these rats. The discriminative stimulus effects of the selective nicotine agonists were blocked by both the general nicotine antagonist mecamylamine and by the selective α4β2* antagonist, dihydro-beta-erythroidine (DHβE). Surprisingly, only DHβE antagonized the rate-suppressing effects of the selective nicotine agonists. These data indicate a selective α4β2* nicotine receptor component to the behavioral effects of arecoline. Although the nicotinic aspects of arecoline's behavior effects could suggest that abuse of arecoline-containing material (e.g. betel nut chewing) is mediated through nicotinic rather than muscarinic actions, further research, specifically on the reinforcing effects of arecoline, is necessary before this conclusion can be supported.