Involvement of the sigma receptor in passive-avoidance learning in the day-old chick during the second wave of neuronal activity

Revisiting the sigma-1 receptor as a biological target to treat affective and cognitive disorders

Depression and cognitive disorders are diseases with complex and not-fully understood etiology. Unfortunately, the COVID-19 pandemic dramatically increased the prevalence of both conditions. Since the current treatments are inadequate in many patients, there is a constant need for discovering new compounds, which will be more effective in ameliorating depressive symptoms and treating cognitive decline. Proteins attracting much attention as potential targets for drugs treating these conditions are sigma-1 receptors. Sigma-1 receptors are multi-functional proteins localized in endoplasmic reticulum membranes, which play a crucial role in cellular signal transduction by interacting with receptors, ion channels, lipids, and kinases. Changes in their functions and expression may lead to various diseases, including depression or memory impairments. Thus, sigma-1 receptor modulation might be useful in treating these central nervous system diseases. Importantly, two sigma-1 receptor ligands entered clinical trials, showing that this compound group possesses therapeutic potential. Therefore, based on preclinical studies, this review discusses whether the sigma-1 receptor could be a promising target for drugs treating affective and cognitive disorders.

Effects of pharmacological inhibition of dopamine receptors on memory load capacity

Memory capacity (MC) refers to the limited capacity of working memory and is defined as the number of elements that an individual can remember for a short retention interval. MC is impaired in many human pathologies, such as schizophrenia and ageing. Fronto-striatal dopamine regulates working memory, through its action on dopamine D1- and D2-like receptors. Human and rodent studies have suggested that MC is improved by D2 dopamine receptor agonists. Although D1 receptors have been crucially involved in the maintenance of working memory during delay, their role in regulating the capacity of WM remains poorly explored. In this study, we tested the effects of systemic injection of the D1-like and D2-like receptor antagonists, SCH 23390 and Haloperidol respectively, on MC in mice. For this, we used a modified version of the object recognition task, the Different/Identical Objects Task (DOT/IOT), which allows the evaluation of MC in rodents. The results showed a negative interaction between the dose of both drugs and the number of objects that could be remembered. The doses of SCH 23390 and Haloperidol that impaired novel object discrimination in the highest memory load condition were about 4 and 3 time lower, respectively, of those impairing performance in the lowest memory load condition. However, while SCH 23390 specifically impaired memory load capacity, the effects of Haloperidol were associated to impairment in exploratory behaviors. These findings may help to predict the cognitive side effects induced by Haloperidol in healthy subjects.

Sigma receptors: potential medications development target for anti-cocaine agents

The ability of cocaine to interact with sigma receptors suggests a viable target for medications development. Recently, numerous novel compounds and antisense oligodeoxynucleotides targeting sigma receptors have been synthesized and shown to prevent the behavioral toxicity and psychomotor stimulant effects of cocaine in animals. Protective doses of sigma receptor antagonists have also been shown to prevent changes in gene expression that are induced by cocaine. Together, the studies provide insight and promising future directions for the development of potential medications for the treatment of cocaine addiction and overdose.