Methamphetamine addiction leads to profound cognitive and emotional impairments through persistent neuroinflammatory and neurodegenerative processes. Recent advances suggest that platelet-derived exosomes possess the potential to promote neurorepair and functional recovery. However, the therapeutic efficacy of exosomes may be influenced by time-of-day administration, given that neural plasticity, blood-brain barrier function, and exosomal dynamics are strongly modulated by diurnal rhythms. Understanding how treatment timing across the daily cycle modulates the neuroprotective and behavioral effects of platelet-derived exosomes is critical to optimizing their therapeutic potential in addiction-related neuropsychiatric disorders. Accordingly, the present study was designed and implemented to evaluate the impact of time-of-day administration in improving the effects of platelet-derived exosomes (pExo) on methamphetamine-induced neurotoxicity. In this study, sixty adult male Wistar rats were divided into five groups and subjected to chronic methamphetamine exposure and subsequent pExo treatment during either the active or the rest phase. Spatial learning and memory were assessed using the Morris water maze, whereas anxiety-like behavior was evaluated through the elevated plus maze and grooming behavior tests. Furthermore, hippocampal indices of cell death, apoptosis, neurogenesis, and neuroinflammation were analyzed. The results demonstrated time-of-day-dependent efficacy of pExo, with administration during the Rest-phase-onset significantly enhancing spatial memory performance (p<0.05), whereas treatment during the active-phase-onset more effectively attenuated anxiety-like behaviors. Moreover, pExo delivery in the Rest-phase-onset led to a greater reduction in apoptosis and a more pronounced induction of neurogenesis relative to the active-phase-onset. However, no significant difference was observed in the expression of Iba1, a marker of neuroinflammation, between the two groups (p=0.35). These findings reveal a time-of-day-dependent modulation of pExo therapy efficacy, suggesting that aligning treatment administration with the rest-activity cycle could optimize neurorestorative outcomes. This time-tailored therapeutic approach may open new avenues for enhancing neural recovery and reducing relapse risk in individuals with substance use disorders.

The consumption of human milk oligosaccharides (HMOs), a key component of breast milk, during early life has been shown to have long-lasting impacts on metabolic processes, immune system function, and nervous system development. The long-term effects of early-life HMO supplementation on behaviours that are associated with metabolic processes, such as food preferences and food choices, and mental health conditions, such as anxiety and depression, are less clear. The present study examined the effects of post-weaning supplementation with two common HMOs, 2'-fucosyllactose (2'FL) and 3'sialyllactose (3'SL), on anxiety-like behavior, sucrose consumption, food preference, and glutamate receptor gene expression in adulthood in Sprague-Dawley rats. We also assessed whether HMO supplementation could attenuate any changes in glutamate receptor gene expression or behavior associated with a high-fat/sucrose (HFS) diet. The present study demonstrated that the effects of HMO supplementation are both sex and dose-dependent, with changes in glutamate receptor gene expression in the nucleus accumbens (NAc) representing the most prominent changes. Effects on sucrose intake were modest and sex-specific, with H/HFS females consuming less sucrose than H/AIN females on the first, but not second, day of testing. This effect was most evident in females that received the high-HMO diet before the HFS challenge and was accompanied by lower GluR1 and GluR2 gene expression in the NAc. Rats fed a HFS diet displayed a preference for palatable food, regardless of early HMO exposure, which may be the result of changes to incentive salience or "wanting" for palatable foods. The findings of this study show a potential link between early-life HMO supplementation, behaviour, and the expression of genes related to synaptic plasticity.

Maternal nutritional environments during early development are thought to influence neurodevelopmental and psychiatric disease susceptibility. While prenatal nutritional effects have been extensively studied within the developmental origins of health and disease (DOHaD) framework, the contribution of postnatal maternal environments remains less understood. In the present study, we investigated whether the postnatal maternal environment influences sensorimotor gating-related behavioral phenotypes and one-carbon metabolism-related metabolites using a cross-fostering paradigm between C57BL/6N (B6) and C3H/HeN (C3) mice, two strains exhibiting distinct prepulse inhibition (PPI) phenotypes. Male offspring were cross-fostered from postnatal day 2 to weaning, and behavioral analyses were performed at 6 weeks of age. Cross-fostering altered PPI responses, particularly in C3 offspring reared by B6 dams. Metabolomic analyses revealed strain-dependent differences in maternal milk metabolites at postnatal day 7 (P7). Maternal milk from B6 dams contained higher levels of methionine and several one-carbon metabolism-related metabolites than milk from C3 dams. Furthermore, cortical methionine and homocysteine levels in the offspring brain were altered by cross-fostering. These findings suggest that the postnatal maternal environment is associated with alterations in offspring one-carbon metabolism. We hypothesize that maternal milk-derived metabolites may represent one potential mechanism underlying these associations.

Adaptive behavior requires knowing when to stop. Internal bodily signals are known to influence intake, yet the mechanisms through which interoceptive signals help terminate intake before harm occurs remain poorly defined. Here, we developed a model of interoceptive prediction to test whether internal signals predicting that continued intake will produce an aversive outcome can regulate consumption below that threshold. Male and female Sprague-Dawley (n=110) self-administered saccharin, and intake exceeding an individualized threshold, defined as 50% of the rat's baseline consumption, was followed by LiCl injection. In Experiment 1, rats receiving response-contingent LiCl progressively approximated their individualized thresholds and maintained intake within 15% above and below those thresholds more frequently than controls that did not receive this contingency. In Experiment 2, neither yoked controls receiving LiCl matched to the timing and frequency of paired titration rats nor partial reinforcement controls receiving LiCl on 50% of sessions showed comparable titration, indicating that titration was not explained by aversive exposure alone. Instead, accurate titration required a predictive contingency between the amount consumed and the aversive consequence. Females adopted a more conservative regulatory strategy than males, maintaining intake near but preferentially below the aversive threshold. These findings establish a behavioral model of interoceptive prediction in intake regulation and provide a framework for investigating how failures in internal-state-guided control may contribute to substance use disorders and other maladaptive behaviors.

Rodent handling methods influence stress, affective state, and behavior in laboratory rodents, which can decrease, but also potentially increase, unwanted variability in outcome measures. Heterospecific play, or tickling, in rats has been proposed as a gentling technique that decreases the stress of handling during experiments, but its effects in adult female and male rats remain unclear. Furthermore, it remains even less understood how tickling might affect subsequent behaviors in experimental tests conducted well after tickling experience. In this study, we examined whether tickling induces positive affect towards experimenters and evaluated subsequent anxiety-like behaviors in adult Sprague Dawley female and male rats. Adult rats underwent either gentle handling via forearm resting or tickling for five consecutive days, with ultrasonic vocalizations recorded during handling sessions. Rats then underwent a human approach test to assess their preference to approach an unfamiliar human hand. Tickling significantly increased the emission of 50-kHz ultrasonic vocalizations and promoted approaches toward an unfamiliar human hand in both female and male rats, indicating enhanced positive affect. In contrast, tickling did not alter anxiety-like behaviors as measured in the open field, elevated zero maze, and light-dark box tests. These findings demonstrate that tickling promotes positive affect and decreased avoidance of human hand interactions in adult female and male rats without influencing subsequent anxiety-related behaviors, supporting its use as a refined gentling technique to reduce handling-related confounds in behavioral research.

Maternal iron deficiency during gestation may have long-lasting effects on offspring neurodevelopment; however, the relationships between behavioral alterations, iron homeostasis, and neurobiological outcomes remain incompletely understood. This study investigated neurobehavioral and neurobiological alterations in offspring rats exposed to maternal gestational iron deficiency despite postnatal nutritional recovery. Female Wistar Kyoto rats were administered either a control or iron-deficient diet throughout gestation, whereas spontaneously hypertensive rats (SHR) served as a phenotypic reference group. Postpartum, all dams and offspring received a standard diet. Behavioral performance was assessed during adolescence using open field, Y-maze, and elevated plus maze tests. Serum iron status, brain and liver iron concentrations, hippocampal brain-derived neurotrophic factor (BDNF), and tropomyosin receptor kinase B (TrkB) protein expression were also evaluated. Maternal gestational iron deficiency was associated with alterations in multiple behavioral outcomes. Offspring exposed to maternal iron deficiency exhibited reduced serum iron concentrations, altered unsaturated iron-binding capacity, and lower brain iron concentrations, whereas liver iron concentrations remained unchanged. Hippocampal BDNF expression was altered in a sex-dependent manner, whereas full-length TrkB expression was unaffected. Several outcomes exhibited sex-dependent patterns. Overall, maternal gestational iron deficiency was associated with persistent neurobehavioral and neurobiological alterations despite postnatal nutritional recovery. These findings suggest that maternal iron availability during gestation may have lasting implications for offspring neurodevelopment and underscore the significance of adequate maternal iron availability during gestation.

Gestational Diabetes (GD) is associated with cognitive dysfunction, anxiety, and post-partum depression. The mechanisms underlying such changes are poorly understood. It is not known whether animal models of GD can replicate the dysfunction observed in humans. In this pilot study, we evaluated whether a streptozotocin (STZ)-induced model of gestational diabetes reproduces postpartum anxiety-like behavior and learning and memory impairments. Female Wistar rats were assigned to the control (n = 14) and STZ (n = 10) groups. After weaning, maternal anxiety behavior was evaluated using the Elevated Plus Maze and Open Field, memory using Novel Object Recognition and Morris Water Maze, and learning using Morris Water Maze. As a post hoc analysis, given its association with memory and learning, hippocampal neurogenesis was evaluated by RT‑qPCR of mRNA levels of Cdk5, Reln, Bdnf, and Gad1 and by estimating the numerical density of DCX‑immunoreactive neurons in the dentate gyrus. No robust behavioral differences were detected between STZ dams and controls in the anxiety-, learning-, and memory-related tasks. Exploratory molecular and histological analyses suggested increased hippocampal BDNF mRNA expression and higher DCX-positive neuronal density in STZ dams, warranting further investigation of hippocampal plasticity-related mechanisms following gestational diabetes.

Analysis of fluid intake microstructure is a powerful tool to provide insight into the mechanisms underlying ingestion. Foundational work demonstrated that changes in the number of licking bursts reflect changes in negative feedback related to satiety, whereas the average size of those bursts reflects changes in the hedonic value of the substance being consumed. These conclusions, however, were drawn primarily from studies of sucrose intake, and it is unclear if the interpretation can be extended to intake of water or sodium. To address this open question, we first tested and found support for the hypothesis that dehydrated rats would show a concentration-dependent decrease in sodium intake that is the result of reduced burst size, without differences in burst number. Next, we tested if a preference for cold water over tepid water was a function of burst size. We found that rats preferred 10°C water over 40°C water, and that the difference in intake was a function of both burst size and burst number. To test this in a condition with a reduced influence of satiation, we repeated this experiment using polydipsic Brattleboro rats. Like the rats in the second experiment, we found that Brattleboro rats preferred 10°C water over 40°C water, but the difference was mediated only by burst size and not burst number. Together, these findings support the conclusion that burst size can be used to measure changes in the hedonic value of sodium and water.

The bidirectional interaction between the gut microbiota and the CNS, referred to as the microbiota-gut-brain axis, has gained recognition as a key regulator of stress responses and neuropsychiatric health. This review synthesizes evidence from preclinical and human studies conducted between 2010 and 2026, setting itself apart from previous reviews by focusing on the bidirectional connection between stress exposure and alterations in gut microbiota. It places particular emphasis on the molecular mechanisms involved, such as neuroinflammation, regulation of the HPA axis, neurotransmitter signaling, and how the microbiota contributes to stress adaptation. Growing evidence from preclinical and clinical research suggests that stress-induced disturbances in gut microbial composition can trigger systemic and neuroinflammation. This occurs through mechanisms such as increased intestinal permeability, translocation of lipopolysaccharides, and activation of TLR4 and NF-κB signaling pathways. Consequently, these immune disruptions adversely affect neurotrophic and neurotransmitter systems such as brain-derived neurotrophic factor (BDNF), serotonin, dopamine, and GABA contributing to anxiety, depression, cognitive impairments, and neurodegenerative conditions. Instead, deliberate modulation of the gut microbiota through probiotics, psychobiotics, fermented foods, and dietary strategies has shown potential to restore microbial balance. Such interventions can help reduce overactivation of the hypothalamic-pituitary-adrenal (HPA) axis, reduce levels of IL-6 and TNF-α, and promote BDNF-driven neuroplasticity. Experimental studies highlight how specific bacterial strains may influence outcomes under stress by enhancing CREB phosphorylation, maintaining tight junction integrity in the gut, and modulating microglial activation. Emerging therapeutic approaches such as fecal microbiota transplantation and postbiotic metabolites, including SCFAs, have also demonstrated promising potential for clinical translation.

Adolescence is a critical period of vulnerability to smoking initiation. However, the neurobiological basis of this association is not well understood. Hence, here we evaluated behavioral parameters, tyrosine hydroxylase content, and catecholamine and corticosterone levels of Swiss mice exposed to nicotine (NIC; 50 μg/mL in 2% saccharin to drink) or vehicle either from postnatal day (PN) 30 to PN46 (adolescents) or from PN75 to PN91 (young adults). Behavioral tests, tissue harvesting, and blood collection occurred in one of three time points: by the end of exposure, after a short withdrawal (4/5 days; SHRT-W) or after a long withdrawal (9/10 days; LNG-W). At SHRT-W, our results in the elevated plus maze (EPM) showed increased anxiety-like behavior in NIC mice when compared to controls, irrespective of age, while, in the open field (OF), an age-independent reduction in anxiety was noted. Adolescent NIC mice showed increased locomotion in the EPM throughout withdrawal, while, in the OF, both adolescent and young adult NIC mice showed increased locomotion at SHRT-W. An age-dependent adolescent-only reduction in corticosterone was observed at SHRT-W in NIC mice. At LNG-W, corticosterone was increased in young adults, particularly in females, compared to controls. The similarity in anxiety-like behavior between adolescents and young adults suggests that the period of vulnerability to nicotine extends beyond the end of adolescence. For the most part, behavioral data failed to reflect changes in neuroendocrine parameters associated with stress response and anxiety. Further investigation of the mechanisms for regulation of behavioral responses to nicotine withdrawal is warranted.

Obesity is associated with reduced dorsolateral prefrontal cortex (DLPFC) activity, a brain region involved in eating behavior regulation. Transcranial direct current stimulation (tDCS) targeting this area may enhance the regulation of appetite and food craving. This study evaluated the effects of a multi-session tDCS protocol combined with nutritional intervention on appetite, food craving, and eating behavior in women with class I and II obesity. In this pilot randomized, triple-blind clinical trial, 22 women were allocated to active or sham stimulation. Participants received 15 tDCS sessions (2 mA, 20 min) over five consecutive days. tDCS was delivered with the anode positioned over the left DLPFC (F3) and the cathode over the right supraorbital region, combined with nutritional education activities. Outcomes included anthropometric measures, body composition, appetite (VAS), food craving (FCQ-S/T), and eating behavior (TFEQ), assessed at baseline, during the intervention, and at 1-, 3-, and 6-month follow-ups. No between-group differences were observed in body weight, BMI, or body composition. The active tDCS group showed a reduction in momentary food craving immediately after the intervention (FCQ-S, p = 0.02) and a sustained decrease in habitual food craving up to six months (FCQ-T, p = 0.01). Changes in TFEQ domains were observed in both groups, suggesting an additional effect of the nutritional intervention. Although the combined protocol did not produce anthropometric changes, it reduced food craving in women with obesity. These findings provide preliminary evidence supporting multi-session tDCS as a promising adjunctive strategy for behavioral modulation in obesity management.

Neonatal handling is an early-life intervention known to produce long-lasting reductions in emotional reactivity and physiological responses to stress in rodents. Although its effects on social behavior remain less well characterized, previous studies have shown that neonatal handling enhances juvenile play behavior, suggesting broader effects on the social behavioral repertoire. The present study examined whether the social effects of neonatal handling observed in younger animals persist into adulthood by assessing social interaction in 10-month-old rats. Social interaction was quantified as time spent in physical contact during two consecutive test sessions following either prolonged social deprivation (seven months of individual housing) or four days of resocialization after the same isolation period. At 2 months of age, we replicated the well-established finding that handled rats showed lower emotional reactivity than non-handled controls in both the open field and elevated plus maze. More importantly, at 10 months of age, handled rats generally spent more time in physical contact than non-handled controls. Although prolonged social deprivation increased social contact in all animals, handled rats generally showed higher levels of vigorous affiliative social interaction. Together with previous findings on juvenile play, these results indicate that neonatal handling produces enduring changes in affiliative social behavior that remain detectable into adulthood and may reflect long-lasting alterations in social motivational processes.

Prenatal stress has recently become known as one of the major factors influencing neurodevelopmental changes resulting in higher susceptibility to drug abuse in adults. The current investigation is aimed at evaluation of the effect of prenatal unpredictable chronic mild stress on susceptibility to apomorphine reward and functioning of 5HT-1A receptors in adulthood in male rats. The female rats were subjected to chronic mild stress from gestational day 6 until parturition. In adult animals, the place preference (CPP), as well as behavioral sensitization to repeated apomorphine (1.0 mg/kg) administration was measured, and the animals underwent behavioral testing and measurement of 5-HT syndrome, followed by analysis of 5HT and 5HIAA content in the hippocampus, hypothalamus, midbrain, and caudate nucleus after injection of 5HT-1A receptor agonist 8-OH-DPAT (1.0 mg/kg). The prenatally stressed animals demonstrated increased preference for the compartment paired with apomorphine and increased behavioral sensitization as compared to control rats, which indicates increased reward susceptibility. Furthermore, prenatally stressed animals displayed increased 5-HT syndrome behavior and lower content of 5HT and 5HIAA in some regions following 8-OH-DPAT challenge. Thus, the prenatal stress increases susceptibility to apomorphine reward through 5HT-1A receptors.