The microbiota–gut–brain axis (MGBA) comprises a complex bidirectional communication network integrating neural, immune, metabolic, and endocrine pathways. Dopamine, traditionally viewed as a central neurotransmitter, also plays essential roles in the gastrointestinal (GI) tract, where it regulates motility, secretion, barrier homeostasis, and mucosal immunity. Growing evidence indicates that the gut microbiota significantly contributes to intestinal dopamine metabolism through specialized enzymatic pathways, particularly tyrosine decarboxylase in Enterococcus species and catechol dehydroxylase in Eggerthella species. These microbial reactions compete with host processes, alter dopaminergic tone, and degrade orally administered levodopa (L-DOPA), providing a mechanistic explanation for the variability in treatment response in Parkinson’s disease (PD). Beyond PD, microbially mediated alterations in dopaminergic signaling have been implicated in mood disorders, neurodevelopmental conditions, metabolic dysfunction, and immune-mediated diseases. This review synthesizes current mechanistic and translational evidence on the dopamine–microbiota interface, outlines microbial pathways shaping dopaminergic activity, and highlights therapeutic opportunities including microbiota modulation, dietary strategies, fecal microbiota transplantation, and targeted inhibitors of microbial dopamine metabolism. Understanding this interface offers a foundation for developing personalized approaches in neurogastroenterology and neuromodulatory therapies.

Background/Objectives: Cholinergic dysfunction plays a central role in memory impairment, yet trihexyphenidyl (THP)-based paradigms remain less explored than scopolamine-based models. This study aimed to characterize a THP-induced cholinergic challenge in a two-trial Y-maze with a 24 h interval and to compare the effects of donepezil and tacrine on recall-phase exploratory allocation. Methods: Male Wistar rats (n = 9/group) were studied in a validation phase including saline, THP 5 mg/kg, and THP 10 mg/kg groups, followed by an intervention phase including control, THP 10 mg/kg, donepezil 1 and 3 mg/kg + THP, and tacrine 3 and 5 mg/kg + THP groups. All treatments were administered intraperitoneally (i.p.). Acquisition- and recall-phase behavior was analyzed. Recall outcomes included arm times, arm entries, the novel-to-familiar arm time ratio (U/K time ratio), the novel-to-familiar arm entry ratio (U/K entry ratio), discrimination indices and time-per-entry indices. Data were analyzed by one-way ANOVA; Tukey’s post hoc test was used in the validation experiment, whereas Dunnett’s test was used in the intervention experiment for comparisons against THP 10. Results: THP at 10 mg/kg produced a robust recall-phase phenotype, with increased familiar-arm exploration, reduced novel-arm exploration and lower normalized indices. Under THP challenge, donepezil was associated with clearer effects at 3 mg/kg, whereas tacrine displayed a broader dose-dependent profile, with the strongest shift in recall-phase exploratory allocation toward the novel arm observed at 5 mg/kg. Conclusions: THP 10 mg/kg produced a robust recall-phase exploratory phenotype in a 24 h two-trial Y-maze paradigm. Under THP challenge, donepezil and tacrine were associated with shifts in recall-phase exploratory allocation. These findings support the potential utility of THP-based paradigms for studying cholinergic disruption in Y-maze settings, while direct comparison with scopolamine-based models remains to be established.

Aluminum chloride (AlCl₃)-induced rat models are widely used to investigate Alzheimer-like neurodegeneration, yet substantial methodological variability limits cross-study comparability. A structured synthesis focused specifically on the methodological architecture of these models, including dose, exposure duration, route of administration, and behavioral assessment, remains lacking. This review aimed to synthesize the behavioral paradigms used to assess learning and memory in rat models of aluminum chloride-induced Alzheimer’s disease, with particular emphasis on dose, duration, and route of administration. A structured narrative review incorporating systematic elements was conducted following PRISMA-informed procedures using PubMed, Web of Science, and Scopus. The reviewed literature showed a predominance of oral administration, low-to-moderate AlCl₃ doses and subchronic exposure durations, most commonly 31–60 days. Behavioral assessment was dominated by hippocampal-dependent paradigms, particularly the Morris water maze and Y-maze. Across studies, AlCl₃ exposure was associated with multidomain behavioral impairment accompanied by consistent hippocampal and cortical histopathological abnormalities and convergent biochemical and molecular changes, including cholinergic dysfunction, oxidative stress, neuroinflammation, and amyloid- and tau-related alterations. Overall, the available literature does not support a standardized experimental protocol or a clear overall dose–effect or duration–effect relationship. Greater harmonization of study design is needed to improve reproducibility and translational relevance.

Background/Objectives: Neuroinflammation is increasingly recognized as an important contributor to Alzheimer-like cognitive impairment. Lipopolysaccharide (LPS) is commonly used in experimental models to trigger systemic immune activation and behavioral alterations associated with neuroinflammation. This study aimed to validate a subacute LPS-induced model of recall-phase impairment and to compare the effects of donepezil and tacrine on recall-related exploratory behavior in rats. Methods: Male Wistar rats were tested in a two-trial Y-maze paradigm consisting of an acquisition trial followed by a recall trial 24 h later. In the validation experiment, rats received saline or LPS 1 mg/kg intraperitoneally for four consecutive days. In the intervention experiment, rats received saline, LPS, or LPS combined with donepezil 1 or 3 mg/kg or tacrine 3 or 5 mg/kg. The primary recall-phase outcome was the unknown/known arm time ratio (U/K time ratio). Additional outcomes included arm times, arm entries, U/K entry ratios, discrimination indices, and mean time per entry. Results: Repeated LPS administration significantly reduced the U/K time ratio, decreased time- and entry-based discrimination indices, reduced time spent in the unknown arm, and decreased unknown-arm entries, without significantly altering acquisition-phase behavior, total entries, or mean time per entry. In the intervention experiment, donepezil 1 mg/kg and tacrine 5 mg/kg significantly increased the U/K time ratio compared with LPS. Discrimination indices and entry-based measures further supported a treatment-related shift toward novelty-directed exploration, while total arm entries and mean time per entry were not significantly changed. Conclusions: Subacute LPS administration produced a measurable recall-phase exploratory impairment in the Y-maze. Donepezil and tacrine attenuated several components of this impairment, with partially distinct dose-related behavioral profiles.

Cholinesterase inhibitors with distinct pharmacological profiles may influence exploratory behavior, yet their effects on recall-related exploration in physiologically intact animals remain insufficiently characterized. The present study aimed to directly compare the effects of donepezil, a relatively selective acetylcholinesterase inhibitor, and tacrine, a cholinesterase inhibitor with broader enzymatic and pharmacological activity, on exploratory allocation during memory recall in healthy rats. Male Wistar rats were assigned to five groups (n = 8/group): control, donepezil 1 mg/kg, donepezil 3 mg/kg, tacrine 3 mg/kg, and tacrine 5 mg/kg. Treatments were administered intraperitoneally 50 min before the acquisition trial, while recall performance was evaluated 24 h later without additional treatment using a two-trial Y-maze paradigm. Time spent and entries into the familiar and novel arms, novel-to-familiar ratios, and mean time per entry were analyzed. Control animals showed no marked preference for the novel arm, whereas donepezil produced only limited, non-significant behavioral changes. Tacrine 5 mg/kg significantly increased the U/K time ratio compared with controls (p = 0.0006) and the U/K entry ratio (p = 0.001), primarily through reduced time spent in the familiar arm (p = 0.0004) and fewer familiar-arm entries (p = 0.025). Absolute time spent in, and entries into, the novel arm did not differ significantly among groups (p = 0.689 and p = 0.883, respectively). Overall, these findings suggest that tacrine, but not donepezil, modified recall-phase exploratory preference in healthy rats, predominantly by reducing persistence in the familiar arm.

Background: Benzodiazepines and non-benzodiazepine hypnotics (Z-drugs) act at the benzodiazepine binding site of GABA_A receptors but differ in their receptor subtype selectivity and behavioural profiles. Diazepam acts as a non-selective positive allosteric modulator of benzodiazepine-sensitive GABA_A receptors, whereas zolpidem and indiplon display preferential affinity for α1-containing receptor subtypes. Although these compounds have been investigated individually in experimental models of exploratory behaviour and cognition, comparative behavioural data obtained using the same experimental protocol remain limited. Methods: This study evaluated the behavioural effects of diazepam, zolpidem and indiplon in male Wistar rats using a two-trial Y-maze paradigm with a 24 h retention interval. Animals received one of three dose levels of each compound before the acquisition trial. Recall-phase behaviour was evaluated using conventional exploration measures together with time- and entry-based preference indices for the previously inaccessible arm. Primary analyses were performed separately for each compound using one-way ANOVA with appropriate post hoc comparisons. Complementary exploratory factorial analyses were subsequently conducted to examine overall behavioural patterns across drug and nominal dose categories. Results: Diazepam produced marked dose-dependent reductions in recall-phase exploration of the previously inaccessible arm and in both exploratory preference indices. In contrast, zolpidem and indiplon reduced exploratory activity during the acquisition phase without significantly affecting recall-phase exploratory behaviour. The complementary factorial analyses identified significant Drug × Nominal Dose Categories interactions across all recall-related endpoints, indicating that behavioural responses across the nominal dose categories differed among the three compound-specific experimental series. The strongest interaction effects were observed for Time Index % (F(6,72) = 10.522, p < 0.001, ηp² = 0.467) and Entries Index % (F(6,72) = 6.870, p < 0.001, ηp² = 0.364). Conclusions: Diazepam produced more pronounced dose-dependent alterations in recall-phase exploratory behaviour than zolpidem or indiplon in the experimental conditions employed. The complementary factorial analyses support the interpretation that the three compounds exhibited different behavioural patterns across the nominal dose categories evaluated, while these exploratory comparisons should be interpreted within the constraints of the study design. Overall, the findings contribute to the comparative behavioural characterization of benzodiazepine-site modulators in the two-trial Y-maze paradigm.