Attention Deficit Hyperactivity Disorder Rats Research Articles

Development and In vivo Evaluation of Atomoxetine Hydrochloride ODMTs in a Nicotine-induced Attention Deficit Hyperactivity Disorder (ADHD) Model in Rats

The current study aimed to evaluate the efficacy of orally administered rapid mini-tablets containing atomoxetine hydrochloride (ODMT) relative to the conventional capsule formulation of atomoxetine hydrochloride (ATO). To mask the bitter taste of ATO and render it more palatable for pediatric administration in individuals with Attention Deficit Hyperactivity Disorder (ADHD), an inclusion complex of ATO with β-cyclodextrin (β-CD) was synthesized. The ODMT and conventional capsule ATO formulations were administered orally to a cohort of ADHD rat pups born to nicotine-exposed dams, facilitating an in vivo efficacy assessment. Behavioral assays, including the open field test, novel object recognition test, and Barnes maze test, were conducted pre- and post-administration of the therapeutics. The outcomes suggested that the ODMT formulation, incorporating ATO-β-CD inclusion complexes, shows promise as a viable alternative to the capsule form of ATO. Conclusively, the preparation of the ATO-β-CD complexes and ODMTs leveraged a factorial experimental design, with the animal model being subjected to nicotine-induced hyperactivity to provide a unique evaluative framework for the ODMT formulation under development.Graphical

Central amygdala is related to the reduction of aggressive behavior by monosodium glutamate ingestion during the period of development in an ADHD model rat.

Monosodium glutamate (MSG), an umami substance, stimulates the gut-brain axis communication via gut umami receptors and the subsequent vagus nerves. However, the brain mechanism underlying the effect of MSG ingestion during the developmental period on aggression has not yet been clarified. We first tried to establish new experimental conditions to be more appropriate for detailed analysis of the brain, and then investigated the effects of MSG ingestion on aggressive behavior during the developmental stage of an ADHD rat model. Long-Evans, WKY/Izm, SHR/Izm, and SHR-SP/Ezo were individually housed from postnatal day 25 for 5 weeks. Post-weaning social isolation (PWSI) was given to escalate aggressive behavior. The resident-intruder test, that is conducted during the subjective night, was used for a detailed analysis of aggression, including the frequency, duration, and latency of anogenital sniffing, aggressive grooming, and attack behavior. Immunohistochemistry of c-Fos expression was conducted in all strains to predict potential aggression-related brain areas. Finally, the most aggressive strain, SHR/Izm, a known model of attention-deficit hyperactivity disorder (ADHD), was used to investigate the effect of MSG ingestion (60 mM solution) on aggression, followed by c-Fos immunostaining in aggression-related areas. Bilateral subdiaphragmatic vagotomy was performed to verify the importance of gut-brain interactions in the effect of MSG. The resident intruder test revealed that SHR/Izm rats were the most aggressive among the four strains for all aggression parameters tested. SHR/Izm rats also showed the highest number of c-Fos + cells in aggression-related brain areas, including the central amygdala (CeA). MSG ingestion significantly decreased the frequency and duration of aggressive grooming and attack behavior and increased the latency of attack behavior. Furthermore, MSG administration successfully increased c-Fos positive cell number in the intermediate nucleus of the solitary tract (iNTS), a terminal of the gastrointestinal sensory afferent fiber of the vagus nerve, and modulated c-Fos positive cells in the CeA. Interestingly, vagotomy diminished the MSG effects on aggression and c-Fos expression in the iNTS and CeA. MSG ingestion decreased PWSI-induced aggression in SHR/Izm, which was mediated by the vagus nerve related to the stimulation of iNTS and modulation of CeA activity.

Bifidobacterium animalis subsp. lactis A6 attenuates hippocampal damage and memory impairments in an ADHD rat model.

Attention deficit hyperactivity disorder (ADHD) is commonly accompanied by learning and memory deficits. This study aimed to demonstrate the effects of probiotic Bifidobacterium animalis subsp. lactis A6 (BAA6) on behaviour and memory function in spontaneously hypertensive rats (SHRs). The results showed that BAA6 treatment ameliorated spatial working memory deficits and inhibited hippocampal neuron loss in SHRs. The levels of neurotransmitters such as acetylcholine, dopamine, and norepinephrine, and the brain derived neurotrophic factor increased and that of glutamate decreased in the brain tissue of SHRs after BAA6 administration. Moreover, BAA6 reduced the levels of pro-inflammatory cytokines TNF-α and IL-1β, and increased the levels of anti-inflammatory IL-10 and antioxidant glutathione in SHRs. 16S rRNA high-throughput sequencing showed that BAA6 treatment changed the gut microbiota composition. BAA6 promoted beneficial Lactobacillus, Romboutsia, Blautia, and Turicibacter, and decreased the enrichment of bacterial genera such as Dietzia, Sporosarcina, Brevibacterium, NK4A214_group, Atopostipes, and Facklamia negatively associated with neurotransmitter release and anti-inflammatory effects in SHRs. Together, these results suggested that BAA6 improved memory function by ameliorating hippocampal damage, abnormal neurotransmitter release and cerebral inflammation by reshaping the gut microbiota in SHRs. This study provides a scientific basis for the development and application of BAA6 as a promising dietary intervention to reduce the risk of ADHD.

Rehmanniae Radix Preparata ameliorates behavioral deficits and hippocampal neurodevelopmental abnormalities in ADHD rat model.

Abnormal hippocampal neurodevelopment, particularly in the dentate gyrus region, may be a key mechanism of attention-deficit/hyperactivity disorder (ADHD). In this study, we investigate the effect of the most commonly used Chinese herb for the treatment of ADHD, Rehmanniae Radix Preparata (RRP), on behavior and hippocampal neurodevelopment in spontaneously hypertensive rats (SHR). Behavior tests, including Morris water maze (MWM) test, open field test (OFT) and elevated plus maze (EPM) test were performed to assess the effect of RRP on hyperactive and impulsive behavior. Hippocampal neurodevelopment was characterized by transmission electron microscopy, immunofluorescence, Golgi staining and Nissl staining approaches. Regulatory proteins such as Trkb, CDK5, FGF2/FGFR1 were examined by Western blot analysis. The results showed that RRP could effectively control the impulsive and spontaneous behavior and improve the spatial learning and memory ability. RRP significantly reduced neuronal loss and increased the number of hippocampal stem cells, and promoted synaptic plasticity. In addition, FGF/FGFR signaling was upregulated after RRP treatment. RRP can effectively reduce impulsive and spontaneous behavior and ameliorate hippocampal neurodevelopmental abnormalities in ADHD rat model.

Low-intensity ultrasound stimulation modulates cortical neurovascular coupling in an attention deficit hyperactivity disorder rat model.

Attention deficit hyperactivity disorder is accompanied by changes in cranial nerve function and cerebral blood flow (CBF). Low-intensity ultrasound stimulation can modulate brain neural activity in attention deficit hyperactivity disorder. However, to date, the modulatory effects of low-intensity ultrasound stimulation on CBF and neurovascular coupling in attention deficit hyperactivity disorder have not been reported. To address this question, Sprague-Dawley, Wistar-Kyoto, and spontaneously hypertensive (attention deficit hyperactivity disorder (ADHD) rat model) rats were divided into the control and low-intensity ultrasound stimulation (LIUS) groups. Cortical electrical stimulation was used to induce cortical excitability in different types of rats, and a penetrable laser speckle contrast imaging (LSCI) system and electrodes were used to evaluate the electrical stimulation-induced CBF, cortical excitability, and neurovascular coupling in free-moving rats. The CBF, cortical excitability, and neurovascular coupling (NVC) under cortical electrical stimulation in the attention deficit hyperactivity disorder rats were significantly different from those in the Sprague-Dawley and Wistar-Kyoto rats. We also found that low-intensity ultrasound stimulation significantly interfered with the cortical excitability and neurovascular coupling induced by cortical electrical stimulation in rats with attention deficit hyperactivity disorder. Our findings suggest that neurovascular coupling is a potential biomarker for attention deficit hyperactivity disorder. Furthermore, low-intensity ultrasound stimulation can improve abnormal brain function in attention deficit hyperactivity disorder and lay a research foundation for its application in the clinical treatment of attention deficit hyperactivity disorder.

Effects of Neuroinflammation and Autophagy on the Structure of the Blood-Brain Barrier in ADHD Model.

Spontaneously hypertensive rats (SHR) are the most common animal model used to study attention deficit hyperactivity disorder (ADHD). The purpose of this study was to look at the impact of neuroinflammation and autophagy on blood-brain barrier function in the prefrontal cortex and hippocampus of ADHD rats. The rats were separated into three groups: juvenile SHR (6weeks), mature SHR (12weeks), and comparable age WKY groups. An open-field test was used to assess rats' ability to move on their own. Immunofluorescence was used to detect the Iba1-immunopositive microglia, ZO-1 and TNF-α. Meanwhile, the expression of p62, Beclin-1, LC3B, and MMP9, MMP2, TNF-α, ZO-1, and occludin were detected by Western blot. The results have shown that Iba1-immunopositive microglia and TNF-α protein in the brain of SHR rats were significantly increased. Moreover, autophagy of cells and the level of MMP2 and MPP9 in the prefrontal cortex and hippocampus increased in SHR rats. In addition, the expression of ZO-1 and occludin was decreased in SHR rats. To sum up, the increase of neuroinflammation and excessive autophagy were essential factors for the damage of blood-brain barrier structure and function.

Delayed Outgrowth in Response to the BDNF and Altered Synaptic Proteins in Neurons From SHR Rats.

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity symptoms. Neuroimaging studies have revealed a delayed cortical and subcortical development pattern in children diagnosed with ADHD. This study followed up on the development in vitro of frontal cortical neurons from Spontaneously hypertensive rats (SHR), an ADHD rat model, and Wistar-Kyoto rats (WKY), control strain, over their time in culture, and in response to BDNF treatment at two different days in vitro (DIV). These neurons were also evaluated for synaptic proteins, brain-derived neurotrophic factor (BDNF), and related protein levels. Frontal cortical neurons from the ADHD rat model exhibited shorter dendrites and less dendritic branching over their time in culture. While pro- and mature BDNF levels were not altered, the cAMP-response element-binding (CREB) decreased at 1 DIV and SNAP-25 decreased at 5 DIV. Different from control cultures, exogenous BDNF promoted less dendritic branching in neurons from the ADHD model. Our data revealed that neurons from the ADHD model showed decreased levels of an important transcription factor at the beginning of their development, and their delayed outgrowth and maturation had consequences in the levels of SNAP-25 and may be associated with less response to BDNF. These findings provide an alternative tool for studies on synaptic dysfunctions in ADHD. They may also offer a valuable tool for investigating drug effects and new treatment opportunities.

Modulation effect of non-invasive transcranial ultrasound stimulation in an ADHD rat model

Objective. Previous studies have demonstrated that transcranial ultrasound stimulation (TUS) with noninvasive high penetration and high spatial resolution has an effective neuromodulatory effect on neurological diseases. Attention deficit hyperactivity disorder (ADHD) is a persistent neurodevelopmental disorder that severely affects child health. However, the neuromodulatory effects of TUS on ADHD have not been reported to date. This study aimed to investigate the neuromodulatory effects of TUS on ADHD. Approach. TUS was performed in ADHD model rats for two consecutive weeks, and the behavioral improvement of ADHD, neural activity of ADHD from neurons and neural oscillation levels, and the plasma membrane dopamine transporter and brain-derived neurotrophic factor (BDNF) in the brains of ADHD rats were evaluated. Main results. TUS can improve cognitive behavior in ADHD rats, and TUS altered neuronal firing patterns and modulated the relative power and sample entropy of local field potentials in the ADHD rats. In addition, TUS can also enhance BDNF expression in the brain tissues. Significance. TUS has an effective neuromodulatory effect on ADHD and thus has the potential to clinically improve cognitive dysfunction in ADHD.

Disturbed relationship between glucocorticoid receptor and 5-HT1AR/5-HT2AR in ADHD rats: A correlation study.

This work is to investigate the alterations of the central 5-hydroxytryptamine (5-HT) system in spontaneously hypertensive rats (SHR) and the correlation with the behaviors of SHR, and to explore the effects of glucocorticoid intervention on the central 5-HT system and SHR behaviors. Three weeks old SHR were chosen as the attention-deficit hyperactivity disorder (ADHD) model and treated with glucocorticoid receptor (GR) agonist or inhibitor, whereas Wista Kyoto rats (WKY) were chosen as the normal control group. Open-field test and Làt maze test were used to evaluate the spontaneous activities and non-selective attention. The levels of 5-HT in the extracellular fluid specimens of the prefrontal cortex of rats were analyzed by high-performance liquid chromatography. The expressions of GR, 5-HT1A receptor (5-HT1AR), and 5-HT2A receptor (5-HT2AR) in the prefrontal cortex were analyzed through immunohistochemistry. Our study demonstrated that the 5-HT level was lower in the prefrontal cortex of SHR compared to that of WKY. The Open-field test and Làt maze test showed that GR agonist (dexamethasone, DEX) intervention ameliorated attention deficit and hyperactive behavior, whereas GR inhibitor (RU486) aggravated the disorders. With DEX, the expression levels of 5-HT and 5-HT2AR in the prefrontal cortex of SHR were significantly higher than those in the control group, whereas the expression level of 5-HT1AR was lower. However, the expression levels of 5-HT and 5-HT2AR were significantly decreased after the intervention with RU486, while the expression level of 5-HT1AR increased. Results showed that glucocorticoid was negatively correlated with 5-HT1AR and positively correlated with 5-HT2AR. In the prefrontal cortex of ADHD rats, the down-regulation of 5-HT and 5-HT2AR expressions and the up-regulation of 5-HT1AR, compared with WYK rats, suggested a dysfunctional central 5-HT system in ADHD rats. The GR agonist can upregulate the expression of 5-HT and 5-HT2AR and downregulate the expression of 5-HT1AR in the prefrontal cortex of SHR as well as reduce the hyperactivity and attention deficit behavior in SHR, while the opposite was true for the GR inhibitor. It is suggested that the dysfunction of the 5-HT system in ADHD rats is closely related to glucocorticoid receptor activity.

Gut metagenomic characteristics of ADHD reveal low Bacteroides ovatus-associated host cognitive impairment

ABSTRACT Attention-deficit/hyperactivity disorder (ADHD) is a highly heterogeneous psychiatric disorder that can have three phenotypical presentations: inattentive (I-ADHD), hyperactive-impulsive (HI-ADHD), and combined (C-ADHD). Environmental factors correlated with the gut microbiota community have been implicated in the development of ADHD. However, whether different ADHD symptomatic presentations are associated with distinct microbiota compositions and whether patients could benefit from the correction of aberrant bacterial colonization are still largely unclear. We carried out metagenomic shotgun analysis with 207 human fecal samples to characterize the gut microbial profiles of patients with ADHD grouped according to their phenotypical presentation. Then, we transplanted the candidate low-abundance bacteria identified in patient subgroups into ADHD rats and evaluated ADHD-associated behaviors and neuronal activation in these rats. Patients with C-ADHD had a different gut microbial composition from that of healthy controls (HCs) (p = .02), but not from that of I-ADHD patients. Eight species became progressively attenuated or enriched when comparing the compositions of HCs to those of I-ADHD and C-ADHD; in particular, the abundance of Bacteroides ovatus was depleted in patients with C-ADHD. In turn, Bacteroides ovatus supplementation ameliorated spatial working memory deficits and reversed θ electroencephalogram rhythm alterations in ADHD rats. In addition, Bacteroides ovatus induced enhanced neuronal activation in the hippocampal CA1 subregion. These findings indicate that gut microbial characteristics that are unique to patients with C-ADHD may be masked when considering a more heterogeneous group of patients. We link the gut microbiota to brain function in an ADHD animal model, suggesting the relevance of testing a potential bacteria-based intervention for some aspects of ADHD.

Effect of Rehmanniae Radix Praeparata on energy metabolism in prefrontal cortex of rats with attention deficit hyperactivity disorder based on "static Yin and dynamic Yang" theory

The present study investigated the effect of Rehmanniae Radix Praeparata(RRP) on the energy metabolism of prefrontal cortex(PFC) of spontaneously hypertensive rats with attention deficit hyperactivity disorder(ADHD) based on the "static Yin and dynamic Yang" theory.Thirty spontaneously hypertensive male rats aged 3 weeks were randomly divided into a model group, a methylphenidate(MPH) group(2 mg·kg~(-1)), and an RRP group(2.4 g·kg~(-1)).Wistar-Kyoto(WKY) male rats of the same age were assigned to the normal group.Rats were treated with corresponding drugs twice per day, and those in the model group and the normal group received the same volume of 0.9% sodium carboxymethyl cellulose(CMC-Na) solution by gavage.The open-field test was performed to evaluate the spontaneous and impulsive behaviors of rats before treatment and on the 4~(th) week after treatment.Four weeks after treatment, PFC was isolated and mitochondria were prepared.The content of adenosine triphosphate(ATP), adenosine diphosphate(ADP), and adenosine monophosphate(AMP) in the PFC was determined by high-performance liquid chromatography(HPLC), and energy charge(EC) was calculated.The parameters related to mitochondrial respiratory function were measured by the Clark oxygen electrode, specifically, state 3 respiration(ST3), state 4 respiration(ST4), and respiratory control rate(RCR).Enzymatic activities of succinate dehydrogenase(SDH), cytochrome C oxidase(COX), Na~+-K~+-ATPase, and Ca~(2+)-Mg~(2+)-ATPase were measured by chemical colorimetry.Mitochondrial permeability transition pore(mPTP) opening was measured by spectrophotometry.Protein expression of glucose transporter 1(GLUT1) and GLUT3 in PFC was tested by Western blot.Compared with the results in the model group, RRP could significantly reduce the total distance of movement, vertical times, and distance in the central area in the open field test(P<0.05 or P<0.01), increase the content of ATP and EC, decrease the content of AMP(P<0.05), elevate ST3 and RCR(P<0.05), potentiate activities of SDH, COX, Na~+-K~+-ATPase, and Ca~(2+)-Mg~(2+)-ATPase(P<0.05 or P<0.01), inhibit the opening of mPTP, and increase the expression levels of GLUT1 and GLUT3 proteins(P<0.05).It was inferred that RRP could inhibit hyperacti-vity and impulsivity by improving the energy metabolism disorder in PFC of ADHD rats, and its mechanism may be related to the improvement of mitochondrial respiratory function, potentiation of Na~+-K~+-ATPase, Ca~(2+)-Mg~(2+)-ATPase, and mitochondrial respiratory enzymes, inhibition of the opening of mPTP, and up-regulation of the expression of glucose transporter proteins.This study initially reveals the biological connotation of the "static Yin and dynamic Yang" theory in ADHD.

Effects of Aberrant miR-384-5p Expression on Learning and Memory in a Rat Model of Attention Deficit Hyperactivity Disorder.

Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric disorder characterized by inattention, hyperactivity, and impulsivity. It may be accompanied by learning difficulties and working memory deficits. Few studies have examined the role of miRNAs in cognitive dysfunction in ADHD. This study investigated the effects of aberrant miR-384-5p expression on learning and memory in a widely used ADHD rat model. Lentiviral vectors were injected into the lateral ventricles of the rats to increase or decrease miR-384-5p level. To determine whether aberrant miR-384-5p expression affects learning and memory, spontaneous activity and cognitive function were assessed with the open field and Morris water maze tests. In the place navigation experiment of the Morris water maze test, time, and total swimming distance to reach the platform decreased compared to the control group when miR-384-5p was overexpressed, whereas down-regulation of miR-384-5p had the opposite effect. There were no obvious changes in brain tissue morphology following miR-384-5p overexpression or inhibition; however, dopamine (DA) receptor D1 (DRD1) level has decreased and increased, respectively, in the prefrontal cortex (PFC). The luciferase activity of the wild-type DRD1 group has decreased in luciferase reporter assay. Cyclic AMP response element-binding protein (CREB) phosphorylation has increased, and DA transporter (DAT) level has decreased in the PFC of spontaneously hypertensive rats (SHR) by miR-384-5p overexpression. On the other hand, miR-384-5p suppression increased DRD1 and decreased DAT and CREB protein levels relative to control rats. These findings suggest that miR-384-5p may play a critical role in learning and memory impairment in ADHD.

Surgery Under General Anesthesia Alleviated the Hyperactivity but Had No Effect on the Susceptibility to PND in ADHD Rats.

Background: Attention-deficit hyperactivity disorder (ADHD) is a typical neuropsychiatric disorder characterized by inattention, impulsivity, and hyperactivity, particularly in children. Recent studies demonstrated a close relationship between the development of ADHD and surgery under general anesthesia. However, few studies illustrated if ADHD symptoms changed after surgery. Meanwhile, whether these individuals with natural neural impairment were sensitive to postoperative neurocognitive disorder (PND) still remain unclear. Methods: Spontaneously hypertensive rats (SHR) were utilized as spontaneous ADHD animal model and Wistar-Kyoto (WKY) rats as non-ADHD animal model. We evaluated the variation of neurocognitive function and locomotor activity of the rats undergoing experimental laparotomy with general anesthesia by isoflurane. Neurocognitive function was assessed by fear conditioning test for contextual memory and Morris water maze (MWM) for spatial memory. Depressive-like behavior after surgery was detected by forced swim test, and open-field test and elevated plus maze test were utilized to evaluate locomotor activities and anxiety. Furthermore, we compared electroencephalogram (EEG) signal in ADHD and WKY rats under free-moving conditions. Afterward, c-Fos staining was also utilized to detect the excitatory activity of neurons in these rats to explore the neural mechanism. Results: Locomotor activity of SHR assessed by average speed and number of line crossings in the open-field test decreased 1 week after surgery under general anesthesia, but there was no difference concerning anxiety levels between SHR and WKY rats after surgery. This phenomenon was also paralleled with the change in EEG signal (delta band 0∼3 Hz). Surgery under general anesthesia had no effect on spatial and contextual memory, while it improved spontaneous depression in SHR. The expression of c-Fos was downregulated for at least 1 week in the nucleus accumbens (NAc) area of ADHD rats’ brain after surgery. Conclusion: ADHD rats were not sensitive to PND. Surgery with general anesthesia could partly improve the hyperactivity symptom of ADHD rats. This mechanism was related to the suppression of neural activity in the cerebral NAc of ADHD rats induced by general anesthetics.

Effect of catalpol on behavior and neurodevelopment in an ADHD rat model

Studies suggest that abnormal neurodevelopment of prefrontal striatal circuits is implicated in the pathogenesis of attention deficit hyperactivity disorder (ADHD). In the present study, we investigated the effect of catalpol, an active ingredient of Rehmanniae radix preparata, which is the most frequently used Chinese medicinal herb for the treatment of ADHD, on behavior and neurodevelopment in spontaneously hypertensive rats (SHR). SHR were divided into SHR group (vehicle, i.g.), methylphenidate (MPH) group (2 mg/kg/day, i.g.), and catalpol group (50 mg/kg/day i.g.), and Wistar-Kyoto (WKY) rats were used as control group (vehicle, i.g.). Open Field Test (OFT) and Morris water maze (MWM) test were performed to assess the effect of catalpol on behavior. Results revealed that both catalpol and MPH treatment decreased average speed, time spent in the central area, rearing times, and central area visits, increased the immobility time of SHR in OFT, and increased number of visits to the annulus, and time spent in target quadrant in the MWM test. Hematoxylin and eosin (H&E) staining showed that catalpol reduced irregular neuronal arrangement, ruptured nuclear membranes, and resulted in disappearance of the nucleolus in the prefrontal cortex (PFC) and striatum of SHR. Moreover, immuno-fluorescent staining of NeuN and myelin basic protein (MBP) indicated that catalpol ameliorated neuronal loss and contributed to myelination. Finally, western blot and immunostaining analysis suggested that several regulatory proteins involved in PFC development were up-regulated by catalpol treatment, such as brain-derived neurotrophic factor (BDNF), cyclin-dependent kinase 5 (Cdk5), p35, fibroblast growth factor (FGF) 21 and its receptor (FGFR)1. Taken together, catalpol can effectively ameliorate hyperactive and impulsive behavior, improve spatial learning and memory in SHR, likely through the neurodevelopmental pathways. Nonetheless, whether catalpol could attenuate inattention in SHR and the pathway by which catalpol reduces neuronal loss remain to be further studied.

Oral Methylphenidate Treatment of an Adolescent ADHD Rat Model Does Not Alter Cocaine-Conditioned Place Preference during Adulthood: A Negative Report.

The stimulant, methylphenidate (MPH), is commonly used to treat attention deficit hyperactivity disorder (ADHD) and has been increasingly prescribed for school age children and adolescents. Concerns regarding its long-term effects on later substance use disorders (SUDs) have been raised. Previous animal studies have produced contradictory results regarding whether early exposure to MPH increases or protects against SUD in adulthood. The goal of our study was to determine if clinically relevant doses of MPH during adolescence alter cocaine responsiveness in adulthood in a rat model of ADHD, the spontaneous hypertensive rat (SHR). We pretreated SHRs with saline or MPH (2.5 mg/kg once or twice day) via oral gavage during their dark cycle from postnatal day 35 (p35) to p44. Adult rats (p80) were assessed in an eight-session cocaine-conditioned place preference test (CPP). Four doses of cocaine were administered via intraperitoneal injection (i.p.) during the conditioning sessions: 1, 5, 10 and 20 mg/kg. Once per day MPH treatment had a small sensitizing effect on baseline general locomotor activity in a novel environment at p80 as well as a limited suppressive effect on reward-specific locomotor activity as measured by the decreased preference to enter the cocaine-paired chamber. This treatment did not have any effect on the amount of time that rats chose to spend in the cocaine-paired chamber. Twice per day MPH treatment had no effect on locomotion or drug-preference. Our results suggest that MPH treatment of ADHD rats during adolescence does not alter preference for cocaine in adulthood.

Expression of BDNF and GDNF in brain of attention deficit hyperactivity disorder rats

Objective To observe the changes of protein and mRNA expression levels of brain derived neurotrophic factor(BDNF) and glial cell line derived neurotrophic factor(GDNF) in the prefrontal cortex, hippocampus and striatum of the attention deficit hyperactivity disorder(ADHD) model animal, and to explore the relationship between BDNF, GDNF and ADHD. Methods Junior spontsneously hyoertensive rat(SHR) rats were used as ADHD model group and Wistar Kyoto rats(WKY) as control group.The protein and mRNA expression levels of BDNF and GDNF in prefrontal cortex, hippocampus and striatum were detected by Western blot and RT-PCR methods. Results The expression of BDNF and GDNF protein was (0.561±0.095) and (0.507±0.155) in the prefrontal cortex, (0.606±0.054) and (0.457±0.198) in hippocampus and (0.558±0.191) and (0.554±0.267) in striatum of SHR rats.The expression of BDNF and GDNF protein of WKY rats were (0.855±0.211) and (0.891±0.244) in the prefrontal cortex, (0.827±0.163) and (0.898±0.207) in hippocampus and (0.998±0.220) and (0.955±0.146) in striatum.The expression of BDNF and GDNF mRNA was (0.636±0.141) and (0.544±0.161) in the prefrontal cortex, (0.996±0.196) and (0.563±0.302) in hippocampus and (0.664±0.145) and (0.689±0.049) in striatum of SHR rats.The expression of BDNF and GDNF mRNA of WKY rats were (0.861±0.232) and (0.840±0.124) in prefrontal cortex, (1.372±0.423) and (1.180±0.441) in hippocampus, and (1.107±0.185) and (0.950±0.247) in striatum.The protein and mRNA expression levels of BDNF and GDNF in prefrontal cortex, hippocampus and striatum of ADHD rats were significantly lower than those in the control group (all P<0.05). Conclusion The low expression of BDNF and GDNF in the prefrontal cortex, hippocampus and striatum of SHR rats may be related to the pathophysiology of ADHD. Key words: Attention deficit hyperactivity disorder; Spontsneously hyoertensive rat; Brain derived neurotrophic factor; Glial cell line derived neurotrophic factor

Effect of glucocorticoid receptor function on the behavior of rats with attention deficit hyperactivity disorder

To investigate the ideal animal models for attention deficit hyperactivity disorder (ADHD) subtypes and the effect of glucocorticoid receptor (GR) function on the behavior of ADHD rats by comparing behavioral differences between spontaneously hypertensive rats (SHRs), Wistar Kyoto (WKY) rats, and Sprague-Dawley (SD) rats. A total of 24 male SHRs aged 21 days were randomly divided into GR agonist group, GR inhibitor group, and SHR group, with 8 rats in each group. Eight male WKY rats and 8 male SD rats, also aged 21 days, were enrolled as WKY group and SD group respectively. The GR agonist group was treated with intraperitoneal injection of dexamethasone (0.5 mg/kg daily); the GR inhibitor group was treated with intraperitoneal injection of mifepristone (RU486) (54 mg/kg daily); the SHR, WKY, and SD groups were treated with intraperitoneal injection of normal saline (0.5 mL/kg daily). The course of treatment was 14 days for all groups. The open field test and Lat maze test were used to evaluate spontaneous activity and non-selective attention. The open field test showed that before drug intervention the SHR group had significantly higher numbers of line crossings and rearings than the WKY and SD groups (P<0.05); the WKY group had a significantly higher number of line crossings than the SD group (P<0.05); the SD group had a significantly higher number of groomings than the WKY group (P<0.05). After drug intervention, the GR agonist group had significantly lower numbers of line crossings and groomings than the SHR group (P<0.05). The Lat maze test indicated that before drug intervention the SHR group had significantly higher numbers of corner crossings and rearings than the WKY and SD groups (P<0.05); the WKY group had significantly higher numbers of rearings and leanings than the SD group (P<0.05). After drug intervention, the GR agonist group had significantly lower numbers of corner crossings and rearings than the SHR group (P<0.05); the GR inhibitor group had a significantly higher number of rearings than the SHR group (P<0.05); the WKY group had significantly higher numbers of rearings and leanings than the SD group (P<0.05). SHR is an ideal animal model for mixed subtype ADHD, and further studies are needed to determine whether WKY rats can be used as an animal model for attention-deficit subtype ADHD. GR agonist can effectively improve spontaneous activity and non-selective attention in SHRs.

Impact of developmental exposure to methylphenidate on rat brain’s immune privilege and behavior: Control versus ADHD model

Attention deficit hyperactivity disorder (ADHD) is the most prevalent childhood mental disorders that often persists into adulthood. Moreover, methylphenidate (MPH) is the mainstay of medical treatment for this disorder. Yet, not much is known about the neurobiological impact of MPH on control versus ADHD conditions, which is crucial to simultaneously clarify the misuse/abuse versus therapeutic use of this psychostimulant.In the present study, we applied biochemical and behavioral approaches to broadly explore the early-life chronic exposure of two different doses of MPH (1.5 and 5 mg/kg/day) on control and ADHD rats (Wistar Kyoto and Spontaneously Hypertensive rats, respectively). We concluded that the higher dose of MPH promoted blood-brain barrier (BBB) permeability and elicited anxiety-like behavior in both control and ADHD animals. BBB dysfunction triggered by MPH was particularly prominent in control rats, which was characterized by a marked disruption of intercellular junctions, an increase of endothelial vesicles, and an upregulation of adhesion molecules concomitantly with the infiltration of peripheral immune cells into the prefrontal cortex. Moreover, both doses of MPH induced a robust neuroinflammatory and oxidative response in control rats. Curiously, in the ADHD model, the lower dose of MPH (1.5 mg/kg/day) had a beneficial effect since it balanced both immunity and behavior relative to vehicle animals.Overall, the contrasting effects of MPH observed between control and ADHD models support the importance of an appropriate MPH dose regimen for ADHD, and also suggest that MPH misuse negatively affects brain and behavior.

Aripiprazole and Riluzole treatment alters behavior and neurometabolites in young ADHD rats: a longitudinal 1H-NMR spectroscopy study at 11.7T

Attention deficit hyperactivity disorder (ADHD), Tourette syndrome (TS) as well as obsessive compulsive disorder (OCD) are co-occurring neurodevelopmental diseases that share alterations of frontocortical neurometabolites. In this longitudinal study we investigated the behavioral and neurochemical effects of aripiprazole and riluzole treatment in juvenile spontaneously hypertensive rats (SHR), a model for ADHD. For neurochemical analysis we employed in vivo magnetic resonance spectroscopy (MRS). Spectra from voxels located at the central striatum and prefrontal cortex were acquired postnatally from day 35 to 50. In the SHR strain only, treatments reduced repetitive grooming and climbing behavior. The absolute quantification of cerebral metabolites in vivo using localized 1H-MRS at 11.7T showed significant alterations in SHR rats compared to controls (including glutamine, aspartate and total NAA). In addition, drug treatment reduced the majority of the detected metabolites (glutamate and glutamine) in the SHR brain. Our results indicate that the drug treatments might influence the hypothesized ‘hyperactive’ state of the cortico-striatal-thalamo-cortical circuitries of the SHR strain. Furthermore, we could show that behavioral changes correlate with brain region-specific alterations in neurometabolite levels in vivo. These findings should serve as reference for animal studies and for the analysis of neurometabolites in selected human brain regions to further define neurochemical alterations in neuropsychiatric diseases.

Glucocorticoids/glucocorticoid receptors effect on dopaminergic neurotransmitters in ADHD rats

Dexamethaone (DEX, glucocorticoid receptor agonist) and RU486 (glucocorticoid receptor inhibitor) may affect the behavior of attention deficit hyperactivity disorder (ADHD) rats, by changing the level of dopamine and noradrenaline and dopamine transporter in different regions of their brain. In this study, we have investigated the effect and the underlying mechanism of Glucocorticoids/Glucocorticoid receptors on dopaminergic neurotransmitters in ADHD Rats. Thirty male Wistar Kyoto rats (WKY) and 30 male spontaneously hypertensive rats (SHR) were respectively divided into 3 groups randomly as follows: a GR agonist group (DEX), a GR inhibitor group (RU486) and a control group (CON). Open field test and Y maze were performed respectively to assess the behavior of the rats. The levels of dopamine, norepinephrine, and dopamine transporter (DAT) in the prefrontal cortex and striatum were also tested. Our results showed that, the behavior of rats were improved after DEX treatment. We also found that the level of DA and NE increased in DEX group, but decreased significantly in RU486 group. Immunohistochemical assay showed that DAT expression level in DEX group was significantly less than that in RU486 and CON group. In conclusion, by regulation of glucocorticoid receptor, GR agonist can decrease DAT expression, resulting in the increase of DA and NE levels in brain that ameliorate hyperactivity and attention deficit in ADHD rats. Our results suggest that the effects of glucocorticoid receptor on dopaminergic neurotransmitter in the central nervous system may be involved in the pathogenesis of ADHD.