Escitalopram attenuates fear stress-induced increase in amygdalar dopamine following methamphetamine-induced sensitisation: Implications of fine-tuning action of selective serotonin reuptake inhibitors on emotional processing

Chromium-functionalized metal-organic frameworks as highly sensitive, dual-mode sensors for real time and rapid detection of dopamine

Dopamine (DA): the brain's "feel-good" chemical that keeps us motivated, happy, and ready to take on the world. This essential neurotransmitter is involved in various physiological processes such as motor control, reward, and mood regulation. Dysregulation of DA levels is linked to several neurodegenerative diseases, emphasizing the need for sensitive and accurate detection methods for both diagnostic and therapeutic purposes. Fluorometric sensing presents an appealing, cost-effective approach to detect DA, especially in complex biological fluids. In this study, we report the synthesis and application of chromium-based metal-organic frameworks (MOFs), Cr-IA and Cr-BTC (IA: itaconic acid and BTC: benzene-1,2,4-tricarboxylic acid), as highly sensitive fluorometric sensors for DA detection in bio-fluids. Cr-IA and Cr-BTC MOFs were synthesized using a solvothermal method with their respective ligands and chromium salts, utilizing a mixed solvent system comprising water, ethanol, and dimethylformamide (DMF). Both MOFs were characterized using a variety of techniques, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), zeta potential measurements, and energy-dispersive X-ray spectroscopy (EDS) that provided essential information on the structural integrity, surface morphology, crystallinity, thermal stability, and surface charge properties of the MOFs, confirming the successful synthesis and characterization of both materials. The synthesized MOFs exhibited remarkable fluorometric sensing capabilities for dopamine detection in HEPES buffer, aqueous solution, and human serum, showcasing strong fluorescence response with high sensitivity, selectivity, and stability across a wide pH range. Cr-IA MOF demonstrated a 3.4-fold fluorescence intensity increase in HEPES buffer, while Cr-BTC MOF achieved a 5-fold enhancement. Both MOFs showed low limits of detection, with Cr-IA and Cr-BTC achieving 21 nM and 41 nM in HEPES buffer, and 26 nM and 20 nM in water, respectively. Fluorescence quenching and visible color changes upon dopamine addition enabled real-time and visual detection, while their dose-response behavior in human serum further validated their reliability for bioanalytical applications. Cytotoxicity studies confirmed their biocompatibility, ensuring their safe use in biological systems. These findings establish Cr-IA and Cr-BTC as highly promising materials for diagnostic and therapeutic monitoring, offering potential for clinical diagnostics and broader biomedical applications.

Effects of chronic haloperidol treatment on the expression of fear memory and fear memory extinction in the cued fear-conditioned rats

AIM

Impairments in emotional memory are frequently observed in several mental disorders, highlighting their significance as potential therapeutic targets. Recent research on the cued fear conditioning model has elucidated the neural circuits involved in fear memory processing. However, contradictory findings have been reported concerning the role of dopamine and the impact of dopamine D2 receptor (D2R) antagonists. There is notably limited knowledge regarding the clinical utility of chronic D2R antagonist treatments. This study aimed to uncover how such treatments affect fear memory processing.

METHODS

We utilized a cued fear conditioning rat model and conducted chronic haloperidol treatment for 14 days. Subsequently, to investigate the effect of chronic haloperidol treatment on fear-conditioned memory expression and extinction, we observed freezing behavior under exposure to a conditioned stimulus for 14 days.

RESULTS

Chronic haloperidol treatment suppressed freezing time on the fear memory expression. In contrast, a single haloperidol administration enhanced the freezing time on fear memory expression and delayed extinction.

CONCLUSION

The results of this study suggest that chronic administration of antipsychotic drugs affects fear memory processing differently from single-dose administration. This indicates that the effects of chronic D2R antagonist treatment are distinct from the nonspecific effects of the drugs. This study provides fundamental insights that may contribute to our understanding of therapeutic mechanisms for fear memory disorders related to D2R in the future.

65 years of research on dopamine's role in classical fear conditioning and extinction: A systematic review

Dopamine, a catecholamine neurotransmitter, has historically been associated with the encoding of reward, whereas its role in aversion has received less attention. Here, we systematically gathered the vast evidence of the role of dopamine in the simplest forms of aversive learning: classical fear conditioning and extinction. In the past, crude methods were used to augment or inhibit dopamine to study its relationship with fear conditioning and extinction. More advanced techniques such as conditional genetic, chemogenic and optogenetic approaches now provide causal evidence for dopamine's role in these learning processes. Dopamine neurons encode conditioned stimuli during fear conditioning and extinction and convey the signal via activation of D1-4 receptor sites particularly in the amygdala, prefrontal cortex and striatum. The coordinated activation of dopamine receptors allows for the continuous formation, consolidation, retrieval and updating of fear and extinction memory in a dynamic and reciprocal manner. Based on the reviewed literature, we conclude that dopamine is crucial for the encoding of classical fear conditioning and extinction and contributes in a way that is comparable to its role in encoding reward.

Critical appraisal and systematic review of genes linked with cocaine addiction, depression and anxiety

Recent lifestyle changes have resulted in tremendous peer pressure and mental stress, and increased the incidences of chronic psychological disorders; like addiction, depression and anxiety (ADA). In this context, the stress-tolerance levels vary amongst individuals and genetic factors play prominent roles. Vulnerable individuals may often be drawn towards drug-addiction to combat stress. This systematic review critically appraises the relationship of various genetic factors linked with the incidences of ADA development. For coherence, we focused solely on cocaine as a substance of abuse in this study. Online scholarly databases were used to screen pertinent literature using apt keywords; and the final retrieval included 42 primary-research articles. The major conclusion drawn from this systematic analysis states that there are 51 genes linked with the development of ADA; and 3 (BDNF, PERIOD2 and SLC6A4) of them are common to all the three aspects of ADA. Further, inter-connectivity analyses of the 51 genes further endorsed the central presence of BDNF and SLC6A4 genes in the development of ADA disorders. The conclusions derived from this systematic study pave the way for future studies for the identification of diagnostic biomarkers and drug targets; and for the development of novel and effective therapeutic regimens against ADA.

GPCR-Based Dopamine Sensors-A Detailed Guide to Inform Sensor Choice for In vivo Imaging

Understanding how dopamine (DA) encodes behavior depends on technologies that can reliably monitor DA release in freely-behaving animals. Recently, red and green genetically encoded sensors for DA (dLight, GRAB-DA) were developed and now provide the ability to track release dynamics at a subsecond resolution, with submicromolar affinity and high molecular specificity. Combined with rapid developments in in vivo imaging, these sensors have the potential to transform the field of DA sensing and DA-based drug discovery. When implementing these tools in the laboratory, it is important to consider there is not a 'one-size-fits-all' sensor. Sensor properties, most importantly their affinity and dynamic range, must be carefully chosen to match local DA levels. Molecular specificity, sensor kinetics, spectral properties, brightness, sensor scaffold and pharmacology can further influence sensor choice depending on the experimental question. In this review, we use DA as an example; we briefly summarize old and new techniques to monitor DA release, including DA biosensors. We then outline a map of DA heterogeneity across the brain and provide a guide for optimal sensor choice and implementation based on local DA levels and other experimental parameters. Altogether this review should act as a tool to guide DA sensor choice for end-users.

Effects of Methcathinone Exposure during Prenatal and Lactational Periods on the Development and the Learning and Memory Abilities of Rat Offspring

This study aimed to investigate the effects of prenatal and lactational methcathinone exposure on the development and the learning and memory abilities of rat offspring using a Sprague-Dawley rat model. Pregnant and lactating rats were administered a consecutive daily dose of methcathinone (0.37 mg/kg) or an equivalent volume of saline by injection on gestational days 7-20 and postnatal days 2-15, respectively. The physical development and neurobehavioral test results of rat pups were recorded throughout the lactation period. Morris water maze (MWM) and novel object recognition (NOR) tests were performed from postnatal day 35 to day 42 to assess the learning and memory abilities of rat offspring in adolescence. The occurrence of hair growth and developments in neurological reflexes, such as improvements in limb grasp, righting reflex, and gait, were delayed in pups after perinatal methcathinone exposure compared with that in the control. Results from MWM and NOR tests indicate that perinatal methcathinone exposure induced deficits in spatial memory, learning ability, and novel object exploration in the adolescent offspring compared with that in the control. The impairment of spatial learning and memory was greater in the prenatal exposure group, while the impairment of novel object exploration was greater in the lactational exposure group. These data show that the prenatal and lactational methcathinone exposure induced the delay of physical and neurological reflex development and impaired learning and memory in rat offspring.

A rotating operant chamber for use with microdialysis

BACKGROUND

Recently, the time resolution of microdialysis followed by a chemical separation for quantitative analysis has improved. The advent of faster microdialysis measurements promises to aid in behavioral research on awake animals. However, microdialysis with awake animals generally employs a fluidic commutator (swivel). The swivel's volume is inimical to the time resolution of the measurements.

NEW METHOD

Animals can be housed in rotating cages so that the swivel is not required, but rotating operant chambers are not available. Here we describe the design and construction of a rotating operant chamber with microdialysis capability. We modified a rotating cage by adding operant behavior testing components to the side of the bowl-shaped cage. A modular on-board controller facilitates operant component/computer communication. A battery provides power to the controller and the operant components. The battery and controller rotate with the cage, and the controller communicates with the computer wirelessly.

RESULTS

The rotating operant chamber can be used to train a rat to retrieve a sucrose pellet following a cue. Microdialysis and online liquid chromatography can be used to measure dopamine at one minute intervals while the rat moves freely and interacts with operant behavior testing components.

COMPARISON WITH EXISTING METHOD(S)

We are not aware of one-minute dopamine measurements in awake animals in an operant chamber.

CONCLUSIONS

Rotating cage modifications are straightforward. One-minute observations of striatal dopamine can be accomplished while an animal is awake, moving, and interacting with its surroundings.

One-step fabrication of a boric acid-functionalized lanthanide metal–organic framework as a ratiometric fluorescence sensor for the selective recognition of dopamine

A boric acid-functionalized Eu-MOF ratiometric fluorescence sensor was prepared for the selective recognition of dopamine.