Exogenous SO2 donor treatment impairs reconsolidation of drug reward memory in mice

Disruption of relapse to cocaine and morphine seeking by LiCl-induced aversive counterconditioning following memory retrieval

Substance use disorder is conceptualized as a form of maladaptive learning, whereby drug-associated memories, elicited by the presence of stimuli related to drug contexts or cues, contribute to the persistent recurrence of craving and the reinstatement of drug-seeking behavior. Hence, use of pharmacology or non-pharmacology way to disrupt drug-related memory holds promise to prevent relapse. Several studies have shown that memories can be unstable and susceptible to modification during the retrieval reactivation phase, termed the "reconsolidation time window". In this study, we use the classical conditioned place preference (CPP) model to investigate the role of aversive counterconditioning on drug-related memories during reconsolidation. Specifically, we uncovered that reconditioning drug cues through counterconditioning with LiCl-induced aversive outcomes following drug memory retrieval reduces subsequent drug-seeking behavior. Notably, the recall of cocaine- or morphine-CPP was eliminated when LiCl-induced aversive counterconditioning was performed 10 min, but not 6 h (outside the reconsolidation time window) after cocaine or morphine memory retrieval. In addition, the effect of LiCl-induced aversive counterconditioning could last for about 14 days. These results suggest that aversive counterconditioning during the reconsolidation of cocaine or morphine memory can prevent the re-seeking of cocaine or morphine, presumably by updating or replacing cocaine or morphine memories with aversive information.

Interfering with reconsolidation by rimonabant results in blockade of heroin-associated memory

Drug-associated pathological memory remains a critical factor contributing to the persistence of substance use disorder. Pharmacological amnestic manipulation to interfere with drug memory reconsolidation has shown promise for the prevention of relapse. In a rat heroin self-administration model, we examined the impact of rimonabant, a selective cannabinoid receptor indirect agonist, on the reconsolidation process of heroin-associated memory. The study showed that immediately administering rimonabant after conditioned stimuli (CS) exposure reduced the cue- and herion + cue-induced heroin-seeking behavior. The inhibitory effects lasted for a minimum of 28 days. The effect of Rimonabant on reduced drug-seeking was not shown when treated without CS exposure or 6 hours after CS exposure. These results demonstrate a disruptive role of rimonabant on the reconsolidation of heroin-associated memory and the therapeutic potential in relapse control concerning substance use disorder.

Drug memory reconsolidation: from molecular mechanisms to the clinical context

Since its rediscovery at the beginning of the 21st Century, memory reconsolidation has been proposed to be a therapeutic target for reducing the impact of emotional memories that can go awry in mental health disorders such as drug addiction (substance use disorder, SUD). Addiction can be conceptualised as a disorder of learning and memory, in which both pavlovian and instrumental learning systems become hijacked into supporting drug-seeking and drug-taking behaviours. The past two decades of research have characterised the details of the molecular pathways supporting the reconsolidation of pavlovian cue-drug memories, with more recent work indicating that the reconsolidation of instrumental drug-seeking memories also relies upon similar mechanisms. This narrative review considers what is known about the mechanisms underlying the reconsolidation of pavlovian and instrumental memories associated with drug use, how these approaches have translated to experimental medicine studies, and the challenges and opportunities for the clinical use of reconsolidation-based therapies.

Sulfur Dioxide: Endogenous Generation, Biological Effects, Detection, and Therapeutic Potential

Significance: Previously, sulfur dioxide (SO₂) was recognized as an air pollutant. However, it is found to be endogenously produced in mammalian tissues. As a new gasotransmitter, SO₂ is involved in regulating the structure and function of blood vessels, heart, lung, gastrointestinal tract, nervous system, etc.Recent Advances: Increasing evidence showed that endogenous SO₂ regulates cardiovascular physiological processes, such as blood pressure control, vasodilation, maintenance of the normal vascular structure, and cardiac negative inotropy. Under pathological conditions including hypertension, atherosclerosis, vascular calcification, aging endothelial dysfunction, myocardial injury, myocardial hypertrophy, diabetic myocardial fibrosis, sepsis-induced cardiac dysfunction, pulmonary hypertension, acute lung injury, colitis, epilepsy-related brain injury, depression and anxiety, and addictive drug reward memory consolidation, endogenous SO₂ protects against the pathological changes via different molecular mechanisms and the disturbed SO₂/aspartate aminotransferase pathway is likely involved in the mechanisms for the earlier mentioned pathologic processes. Critical Issues: A comprehensive understanding of the biological effects of endogenous SO₂ is extremely important for the development of novel SO₂ therapy. In this review, we summarized the biological effects, mechanism of action, SO₂ detection methods, and its related prodrugs. Future Directions: Further studies should be conducted to understand the effects of endogenous SO₂ in various physiological and pathophysiological processes and clarify its underlying mechanisms. More efficient and accurate SO₂ detection methods, as well as specific and effective SO₂-releasing systems should be designed for the treatment and prevention of clinical related diseases. The translation from SO₂ basic medical research to its clinical application is also worthy of further study. Antioxid. Redox Signal. 36, 256-274.

Sulfur dioxide derivatives attenuates consolidation of contextual fear memory in mice

Post-traumatic stress disorder (PTSD) is characterized by an enhancement of traumatic memory. Intervention strategies based on the different stages of memory have been shown to be effective in the prevention and control of PTSD. The endogenous gaseous molecule, sulfur dioxide (SO₂), has been reported to significantly exert neuromodulatory effects; however, its regulation of learning and memory remains unestablished. This study aimed to investigate the effects of exogenous SO₂ derivatives administration on the formation, consolidation, reconsolidation, retention, and expression of contextual fear memory. Behavioral results showed that both intraperitoneal injection (50 mg/kg, ip) and hippocampal infusion (5 μg/side) of SO₂ derivatives (a mixture of sodium sulfite and sodium bisulfite, Na₂SO₃/NaHSO₃, 3:1 M/M) significantly impaired consolidation but had no effect on reconsolidation and retention of contextual fear memory. These findings suggest that the attenuating effects of SO₂ on the consolidation of fear memory involves, at least partially, the region of the hippocampus. The findings of this study provide direct evidence for the development of new strategies for PTSD prevention and treatment involving the use of gaseous SO₂.

Urocanic acid enhances memory consolidation and reconsolidation in novel object recognition task

Urocanic acid (UCA) is an endogenous small molecule that is elevated in skin, blood and brain after sunlight exposure, mainly playing roles in the periphery systems. Few studies have investigated the role of UCA in the central nervous system. In particular, its role in memory consolidation and reconsolidation is still unclear. In the present study, we investigated the effect of intraperitoneal injection of UCA on memory consolidation and reconsolidation in a novel object recognition memory (ORM) task. In the consolidation version of the ORM task, the protocol involved three phases: habituation, sampling and test. UCA injection immediately after the sampling period enhanced ORM memory performance; UCA injection 6 h after sampling did not affect ORM memory performance. In the reconsolidation version of the ORM task, the protocol involved three phases: sampling, reactivation and test. UCA injection immediately after reactivation enhanced ORM memory performance; UCA injection 6 h after reactivation did not affect ORM memory performance; UCA injection 24 h after sampling without reactivation did not affect ORM memory performance. This UCA-enhanced memory performance was not due to its effects on nonspecific responses such as locomotor activity and exploratory behavior. The results suggest that UCA injection enhances consolidation and reconsolidation of an ORM task, which further extends previous research on UCA effects on learning and memory.

Blockade of β-Adrenergic Receptors by Propranolol Disrupts Reconsolidation of Drug Memory and Attenuates Heroin Seeking

Persistent traces of drug reward memories contribute to intense craving and often trigger relapse. A number of pharmacological interventions on drug-associated memories have shown significant benefits in relapse prevention at a preclinical level but their translational potential is limited due to deleterious side effects. Propranolol, a non-specific β-adrenergic receptors antagonist, is known for its ability to erase maladaptive memories associated with nicotine or cocaine in rodents and humans. However, little is known about its effect on reconsolidation of heroin memory and heroin seeking. In the present study, rats with a history of intravenous heroin self-administration received the propranolol treatment (10 mg/kg; i.p.) at different time windows with or without CS (conditioned stimulus) exposure. Our results showed that propranolol, when administered immediately after CS exposure but not 6 h later, can significantly attenuate cue-induced and drug-primed reinstatement of heroin seeking, suggesting that propranolol has the ability to disrupt heroin memory and reduce relapse. The propranolol treatment without retrieval of drug memory had no effect on subsequent reinstatement of heroin seeking, suggesting that its interfering effects are retrieval-dependent. Importantly, the effects of propranolol were long lasting as rats showed diminished drug seeking even 28 days after the treatment. Altogether, our study suggests that propranolol can interfere with reconsolidation of heroin memory and reduce subsequent drug seeking, making it an attractive therapeutic candidate for the treatment of opioid addiction and relapse prevention.