Orbitofrontal cortex to dorsal striatum circuit is critical for incubation of oxycodone craving after forced abstinence.

Relapse is a major challenge in treating opioid addiction, including oxycodone. During abstinence, oxycodone seeking progressively increases, a phenomenon termed incubation of oxycodone craving. We previously demonstrated a causal role of orbitofrontal cortex (OFC) in this incubation. Here, we studied the interaction between glutamatergic projections from OFC and dopamine 1-family receptor (D1R) signaling in dorsal striatum (DS) in this incubation in male rats. We first examined the causal role of D1R signalling in DS in incubated oxycodone seeking. Next, we combined fluorescence-conjugated cholera toxin subunit B (CTb-555, a retrograde tracer) with Fos (a neuronal activity marker) to assess whether the activation of OFC→DS projections was associated with incubated oxycodone seeking. We then used a pharmacological asymmetrical disconnection procedure to examine the role of the interaction between projections from OFC and D1R signalling in DS in incubated oxycodone seeking. We also tested the effect of unilateral pharmacological inactivation of OFC or unilateral D1R blockade of DS on incubated oxycodone seeking. Finally, we assessed whether contralateral disconnection of OFC→DS projections impacted non-incubated oxycodone seeking on abstinence day 1. We found that D1R blockade in DS decreased incubated oxycodone seeking and OFC→DS projections were activated during incubated oxycodone seeking. Moreover, anatomical disconnection of OFC→DS projections, but not unilateral inactivation of OFC or unilateral D1R blockade in DS, decreased incubated oxycodone seeking. Lastly, contralateral disconnection of OFC→DS projections had no effect on oxycodone seeking on abstinence day 1. Together, these results demonstrated a causal role of OFC→DS projections in incubation of oxycodone craving.

Microdialysis perfusion of COA-Cl enhances dopamine metabolism in the dorsal striatum of freely moving mice.

We performed a microdialysis study to examine the effects of local perfusion of COA­Cl on the extracellular levels of dopamine (DA) and its metabolites in the dorsal striatum of mice in vivo. The mice were perfused with Ringer's solution (control) and COA­Cl (0.05, 0.1, or 0.5 mM) into the dorsal striatum. Dialysate samples were collected every 30 min and then analyzed using high­performance liquid chromatography coupled with an electrochemical detector. We found that local perfusion of COA­Cl (0.1 or 0.5 mM) into the dorsal striatum of living mice produced a significant and dose­dependent increase in extracellular levels of DA, 3­methoxytyramine (3­MT), and homovanillic acid (HVA), where only 0.5 mM COA­Cl increased dihydroxyphenylacetic acid (DOPAC) levels. However, 0.05 mM of COA­Cl did not significantly affect either DA levels or its metabolites. Then, we administered the monoamine oxidase (MAO) inhibitor clorgyline alone or in combination with COA­Cl (0.1 mM) to test whether COA­Cl­induced increases in DOPAC and HVA are mediated by increased MAO activity. Clorgyline alone increased 3­MT levels and decreased DOPAC and HVA levels but not DA levels. When combined with COA­Cl, clorgyline increased 3­MT levels and reversed the decrease in DOPAC and HVA levels caused by clorgyline. The increase in DA metabolism induced by COA­Cl suggests that some DA was further metabolized into DOPAC, 3­MT, and HVA. This indicates that COA­Cl plays a role in DA metabolism via increased DA release and/or activation of MAO, offering new insights into the effects of COA­Cl on DA metabolism in the brain.

Impact of 5-Lipoxygenase Deficiency on Dopamine-Mediated Behavioral Responses.

The 5-lipoxygenase/leukotriene system has been implicated in both physiological and pathological states within the central nervous system. Understanding how this system interacts with the dopaminergic system could provide valuable insights into dopamine-related pathologies. This study focused on examining both motor and non-motor dopamine-related responses in 5-lipoxygenase/leukotriene-deficient mice. We used pharmacological agents such as amphetamine, apomorphine, and reserpine to challenge the dopaminergic system, evaluating their effects on prepulse inhibition reaction (PPI), general motor activity, and oral involuntary movements. Additionally, we analyzed striatal glial marker expression (GFAP and Iba-1) in reserpine-treated mice. The 5-lipoxygenase/leukotriene-deficient mice exhibited increased spontaneous locomotor activity, including both horizontal and vertical exploration, along with stereotyped behavior compared to wild-type mice. This hyperactivity was reduced by acute apomorphine treatment. Although basal PPI responses were unchanged, 5-lipoxygenase/leukotriene-deficient mice displayed a significant reduction in susceptibility to amphetamine-induced PPI disruption. Conversely, these mice were more vulnerable to reserpine-induced involuntary movements. There were no significant differences in the basal expression of striatal GFAP and Iba-1 positive cells between 5-lipoxygenase/leukotriene-deficient and wild-type mice. However, reserpine treatment significantly increased GFAP immunoreactivity in wild-type mice, an effect not observed in 5-lipoxygenase-deficient mice. Additionally, the percentage of activated microglia was significantly higher in reserpine-treated wild-type mice, an effect absents in 5-lipoxygenase/leukotriene-deficient mice. Our findings suggest that 5-lipoxygenase/leukotriene deficiency leads to a distinctive dopaminergic phenotype, indicating that leukotrienes may influence the modulation of dopamine-mediated responses.

Chronic pramipexole and rasagiline treatment enhances dendritic spine structural neuroplasticity in striatal and prefrontal cortex neurons of rats with bilateral intrastriatal 6-hydroxydopamine lesions.

Parkinson's disease manifests as neurological alterations within dendritic spines in the striatal and neocortical brain regions, where their functionality closely correlates with morphology. However, the impact of current pharmacotherapy on dendritic spine neuroplasticity, crucial for novel drug development in neurological and psychiatric disorders, remains unclear. This study investigated the effects of 6-OHDA intrastriatal bilateral lesions in male adult rats on behavior and dendritic spine neuroplasticity in striatal and cortical neurons. Furthermore, it evaluated the influence of chronic co-administration of pramipexole (PPX), a D3 receptor agonist, and rasagiline (Ras), a selective MAO-B inhibitor, on these alterations. Lesioned animals exhibited impaired balance behavior, with no improvement following PPX-Ras treatment. The 6-OHDA lesion decreased dendritic spine density in caudate putamen (CPU) spiny projection neurons (SPNs), a change unaffected by treatment, though PPX-Ras increased mushroom spines and reduced stubby spines in these neurons. In nucleus accumbens (NAcc) SPNs and prefrontal cortex layer 3 (PFC-3) pyramidal cells, dendritic spine density remained unaltered, but PPX-Ras decreased mushroom spines and increased bifurcated spines in the NAcc, while increasing mushroom spines and decreasing stubby spines in PFC-3 in lesioned rats. These findings emphasize the importance of dendritic spines as promising targets for innovative pharmacotherapies for Parkinson's disease.

Preexisting risk-avoidance and enhanced alcohol relief are driven by imbalance of the striatal dopamine receptors in mice.

Alcohol use disorder (AUD) is frequently comorbid with anxiety disorders, yet whether alcohol abuse precedes or follows the expression of anxiety remains unclear. Rodents offer control over the first drink, an advantage when testing the causal link between anxiety and AUD. Here, we utilized a risk-avoidance task to determine anxiety-like behaviors before and after alcohol exposure. We found that alcohol's anxiolytic efficacy varied among inbred mice and mice with high risk-avoidance showed heightened alcohol relief. While dopamine D1 receptors in the striatum are required for alcohol's relief, their levels alone were not correlated with relief. Rather, the ratio between striatal D1 and D2 receptors was a determinant factor for risk-avoidance and alcohol relief. We show that increasing striatal D1 to D2 receptor ratio was sufficient to promote risk-avoidance and enhance alcohol relief, even at initial exposure. Mice with high D1 to D2 receptor ratio were more prone to continue drinking despite adverse effects, a hallmark of AUD. These findings suggest that an anxiety phenotype may be a predisposing factor for AUD.

Methylphenidate reduces spatial attentional bias by modulating fronto-striatal connectivity.

Spatial attention bias reflects tendency to direct attention to specific side in space. This bias reflects asymmetric dopamine (DA) signaling in the striatum. Administration of DA agonists reduces spatial bias, yet the underlying mechanism is not yet clear. To address this, the current study tested whether methylphenidate (MPH; an indirect DA agonist) reduces orienting bias by modulating fronto-striatal connectivity. 54 adults with consistent bias completed the greyscales task which detects subtle biases during fMRI scanning under MPH (20 mg) or placebo, in a double-blind design. As hypothesized, MPH reduced bias by increasing orienting towards non-preferred hemispace, regardless of whether the initial bias was left or right. MPH-induced increases were found in activation of the medial superior frontal gyrus (mSFG: F[1;53] = 4.632, cluster-defining threshold of P < 0.05, minimal cluster size = 0, p_FWE = 0.036, η2 = 0.08) and its functional connectivity with the caudate (left caudate: F[1;53] = 12.664, p_FWE = 0.001, η2 = 0.192; right caudate: F[1;53] = 11.069, p_FWE = 0.002, η2 = 0.172), when orienting towards the non-preferred hemispace. MPH also reduced mSFG activation and fronto-striatal connectivity for the preferred hemispace. Results suggest modulation of frontal excitability due to increased caudate-mSFG functional connectivity. This mechanism may underlie the positive effect of dopaminergic agonists on abnormal patterns of directing attention in space.

Different development patterns of reward behaviors induced by ketamine and JWH-018 in striatal GAD67 knockdown mice.

IMPORTANCE: Glutamic acid decarboxylase 67 (GAD67) is a gamma-aminobutyric acid (GABA) synthesis enzyme associated with the function of other neurotransmitter receptors, such as the N-methyl-D-aspartate (NMDA) receptor and cannabinoid receptor 1. However, the role of GAD67 in the development of different abused drug-induced reward behaviors remains unknown. In order to elucidate the mechanisms of substance use disorder, it is crucial to study changes in biomarkers within the brain's reward circuit induced by drug use. OBJECTIVE: The study was designed to examine the effects of the downregulation of GAD67 expression in the dorsal striatum on reward behavior development. METHODS: We evaluated the effects of GAD67 knockdown on depression-like behavior and anxiety using the forced swim test and elevated plus maze test in a mouse model. We further determined the effects of GAD67 knockdown on ketamine- and JWH-018-induced conditioned place preference (CPP). RESULTS: Knockdown of GAD67 in the dorsal striatum of mice increased depression-like behavior, but it decreased anxiety. Moreover, the CPP score on the NMDA receptor antagonist ketamine was increased by GAD67 knockdown, whereas the administration of JWH-018, a cannabinoid receptor agonist, did not affect the CPP score in the GAD67 knockdown mice group compared with the control group. CONCLUSIONS AND RELEVANCE: These results suggest that striatal GAD67 reduces GABAergic neuronal activity and may cause ketamine-induced NMDA receptor inhibition. Consequently, GAD67 downregulation induces vulnerability to the drug reward behavior of ketamine.

Vitexin Mitigates Haloperidol-Induced Orofacial Dyskinesia in Rats through Activation of the Nrf2 Pathway.

Vitexin (VTX), a C-glycosylated flavone found in various medicinal herbs, is known for its antioxidant, anti-inflammatory, and neuroprotective properties. This study investigated the protective effects of VTX against orofacial dyskinesia (OD) in rats, induced by haloperidol (HPD), along with the neuroprotective mechanisms underlying these effects. OD was induced by administering HPD (1 mg/kg i.p.) to rats for 21 days, which led to an increase in the frequency of vacuous chewing movements (VCMs) and tongue protrusion (TP). VTX (10 and 30 mg/kg) was given intraperitoneally 60 min after each HPD injection during the same period. On the 21st day, following assessments of OD, the rats were sacrificed, and nitrosative and oxidative stress, antioxidant capacity, mitochondrial function, neuroinflammation, and apoptosis markers in the striatum were measured. HPD effectively induced OD, while VTX significantly reduced HPD-induced OD, decreased oxidative stress, enhanced antioxidant capacity, prevented mitochondrial dysfunction, and reduced neuroinflammatory and apoptotic markers in the striatum, and the protective effects of VTX on both behavioral and biochemical aspects of HPD-induced OD were significantly reduced when trigonelline (TGN), an inhibitor of the nuclear factor erythroid-2-related factor 2 (Nrf2)-mediated pathway, was administered. These findings suggest that VTX provides neuroprotection against HPD-induced OD, potentially through the Nrf2 pathway, indicating its potential as a therapeutic candidate for the prevention or treatment of tardive dyskinesia (TD) in clinical settings. However, further detailed research is required to confirm these preclinical findings and fully elucidate VTX's therapeutic potential in human studies.

The Effect of Chronic Treatment with the Inhibitor of Phosphodiesterase 5 (PDE5), Sildenafil, in Combination with L-DOPA on Asymmetric Behavior and Monoamine Catabolism in the Striatum and Substantia Nigra of Unilaterally 6-OHDA-Lesioned Rats.

The use of phosphodiesterase inhibitors in the treatment of Parkinson's disease is currently widely discussed. The study aimed to investigate the impact of acute and chronic treatment with the phosphodiesterase 5 inhibitor, sildenafil, at low and moderate doses of 2 mg/kg and 6 mg/kg, and L-DOPA (12.5 mg/kg), alone or in combination, on asymmetric behavior and dopamine (DA) and serotonin metabolism in the striatum and substantia nigra of unilaterally 6-OHDA-lesioned rats. Acute administration of sildenafil at both tested doses jointly with L-DOPA significantly increased the number of contralateral rotations during a 2 h measurement compared to L-DOPA alone. The effect of a lower dose of sildenafil combined with L-DOPA was much greater in the second hour of measurement. However, the acute combined administration of a higher dose of sildenafil with L-DOPA resulted in an immediate and much stronger increase in the number of contralateral rotations compared to L-DOPA alone, already visible in the first hour of measurement. Interestingly, the chronic combined administration of 2 mg/kg of sildenafil and L-DOPA significantly reduced the number of contralateral rotations, especially during the first hour of measurement, compared to the long-term treatment with L-DOPA alone. Such an effect was not observed after the long-term combined treatment of a higher dose of sildenafil and L-DOPA compared to L-DOPA alone. The concentration of DA in the ipsilateral striatum and substantia nigra after the last combined chronic dose of sildenafil (2 or 6 mg/kg) and L-DOPA (12.5 mg/kg) was significantly higher than after L-DOPA alone. In spite of much stronger increases in the DA concentration in the ipsilateral striatum and substantia nigra, the number of contralateral rotations was reduced in the group of rats treated with the combination of 2 mg/kg sildenafil and L-DOPA compared to the group receiving L-DOPA alone. Moreover, the combined treatment with a low dose of sildenafil and L-DOPA had an opposite effect on DA catabolism, as assessed by DOPAC/DA and HVA/DA indexes, and these indexes were reduced in the ipsilateral striatum but increased in the contralateral striatum and substantia nigra compared to the treatment with L-DOPA alone. The results of the present study show that the addition of a low dose of a PDE5 inhibitor to the standard L-DOPA therapy differently modulates rotational behavior, the tissue DA concentration and its catabolism in the striatum and substantia nigra.

Early expression of monomeric and oligomeric alpha-synuclein and reduction of tyrosine hydroxylase following intranigral injection of lipopolysaccharide.

BACKGROUND: The insoluble tangles of alpha-synuclein (α-syn) protein in the nigrostriatal circuit, characteristic of synucleinopathy, originate from low molecular weight oligomers, whose appearance and dissemination are related to neuroinflammation. These oligomeric forms of α-syn are considered highly cytotoxic but transient, so knowing the timing in which they appear remains challenging. Therefore, this study aimed to analyze the abundance of oligomeric forms of α-syn and tyrosine hydroxylase (TH) between 3 and 7 days after inducing neuroinflammation with lipopolysaccharide (LPS). METHODS AND RESULTS: LPS (2.5 µg/2.5 µL) was stereotaxically injected in the substantia nigra (SN) of adult male Wistar rats, which were sacrificed 3, 5 and 7 days after this intervention. The brains were processed for semi quantitative Western blot, along with brains from control and sham animals. Our results show an increased expression of α-syn monomer (15 kDa) only 3 days after LPS infusion, and the formation of 50 KDa and 60 kDa α-syn oligomers in the SN and striatum (STR) between 3 and 7 days after LPS infusion. Furthermore, the presence of these oligomers was accompanied by a decrease in the expression of nigral TH. CONCLUSION: These findings highlight the rapidity with which potentially toxic forms of α-syn appear in the nigrostriatal circuit after a neuroinflammatory challenge, in addition to allowing us to identify specific oligomers and a temporal relation with neurodegeneration of TH-positive cells. Knowledge of the timing and location in which these small oligomers appear is essential to developing therapeutic strategies to prevent its formation.

Parthenolide ameliorates 3-nitropropionic acid-induced Huntington's disease-like aberrations via modulating NLRP3 inflammasome, reducing microglial activation and inducing astrocyte shifting.

BACKGROUND: Huntington's disease (HD) is a progressive neurodegenerative disease that causes motor, cognitive, and psychiatric abnormalities, with no satisfying disease-modifying therapy so far. 3-nitropropionic acid (3NP) induces behavioural deficits, together with biochemical and histological alterations in animals' striata that mimic HD. The role of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome in HD pathogenesis remains largely uncharacterized. Parthenolide (PTL), a naturally occurring nuclear factor kappa B (NF-κB) inhibitor, is also known to inhibit NLRP3 inflammasome. Whether PTL is beneficial in HD has not been established yet. AIM: This study evaluated the possible neuroprotective effects of PTL against 3NP-induced behavioural abnormalities, striatal biochemical derangements, and histological aberrations. METHODS: Male Wistar rats received PTL (0.5 mg/kg/day, i.p) for 3 weeks and 3NP (10 mg/kg/day, i.p) was administered alongside for the latter 2 weeks to induce HD. Finally, animals were subjected to open-field, Morris water maze and rotarod tests. Rat striata were examined histologically, striatal protein expression levels of glial fibrillary acidic protein (GFAP), cluster of differentiation 45 (CD45) and neuron-specific enolase (NSE) were evaluated immunohistochemically, while those of interleukin (IL)-1ß, IL-18, ionized calcium-binding adapter molecule-1 (Iba1) and glutamate were determined by ELISA. Striatal nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein (Keap1), NF-κB, NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, S100 calcium-binding protein A10 (S100A10) and complement-3 (C3) were assessed by gene expression analysis. RESULTS: PTL improved motor, locomotor, cognitive and anxiety-like behaviours, restored neuronal integrity, upregulated Nrf2, and inhibited NLRP3 inflammasome, NF-κB and microglial activation. Additionally, PTL induced astrocyte shifting towards the neuroprotective A2 phenotype. CONCLUSION: PTL exhibits neuroprotection against 3NP-induced HD, that might be ascribed, at least in part, to its modulatory effects on Keap1/Nrf2 and NF-κB/NLRP3 inflammasome signaling.

Oxytocin Protects Nigrostriatal Dopamine Signal via Activating GABAergic Circuit in the MPTP-Induced Parkinson's Disease Model.

The most pronounced neuropathological feature of Parkinson's disease (PD) is the loss of dopamine (DA) neurons in the substantia nigra compacta (SNc), which depletes striatal DA. Hypothalamic oxytocin is found to be reduced in PD patients and closely interacts with the DA system, but the role of oxytocin in PD remains unclear. Here, the disturbances of endogenous oxytocin level and the substantia nigra (SN) oxytocin receptor expression in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model is observed, correlated with the striatal tyrosine hydroxylase (TH) expression reduction. Killing/silencing hypothalamic oxytocin neurons aggravates the vulnerability of nigrostriatal DA signal to MPTP, whereas elevating oxytocin level by intranasal delivery or microinjecting into the SN promotes the resistance. In addition, knocking out SN oxytocin receptors induces the time-dependent reductions of SNc DA neurons, striatal TH expression, and striatal DA level by increasing neuronal excitotoxicity. These results further uncover that oxytocin dampens the excitatory synaptic inputs onto DA neurons via activating oxytocin receptor-expressed SN GABA neurons, which target GABA(B) receptors expressed in SNc DA neuron-projecting glutamatergic axons, to reduce excitotoxicity. Thus, besides the well-known prosocial effect, oxytocin acts as a key endogenous factor in protecting the nigrostriatal DA system.

Intra-striatal infusion of the small molecule alpha-synuclein aggregator, FN075, does not enhance parkinsonism in a subclinical AAV-alpha-synuclein rat model.

Numerous challenges hinder the development of neuroprotective treatments for Parkinson's disease, with a regularly identified issue being the lack of clinically relevant animal models. Viral vector overexpression of α-synuclein is widely considered the most relevant model; however, this has been limited by high variability and inconsistency. One potential method of optimisation is pairing it with a secondary insult such as FN075, a synthetic molecule demonstrated to accelerate α-synucleinopathy. Thus, the aim of this study was to investigate if sequential infusion of adeno-associated virus (AAV)-α-synuclein and FN075 into the rat brain can replicate α-synucleinopathy, nigrostriatal pathology and motor dysfunction associated with Parkinson's disease. Rats received a unilateral injection of AAV-α-synuclein (or AAV-green fluorescent protein) into two sites in the substantia nigra, followed 4 weeks later by unilateral injection of FN075 (or vehicle) into the striatum. Animals underwent behavioural testing every 4 weeks until sacrifice at 20 weeks, followed by immunohistochemistry assessment post-mortem. As anticipated, AAV-α-synuclein led to extensive overexpression of human α-synuclein throughout the nigrostriatal pathway, as well as elevated levels of phosphorylated and aggregated forms of the protein. However, the sequential administration of FN075 into the striatum did not exacerbate any of the α-synuclein pathology. Furthermore, despite the extensive α-synuclein pathology, neither administration of AAV-α-synuclein nor FN075, alone or in combination, was sufficient to induce dopaminergic degeneration or motor deficits. In conclusion, this approach did not replicate the key characteristics of Parkinson's disease, and further studies are required to create more representational models for testing of novel compounds and treatments for Parkinson's disease.

Methylphenidate Exposing During Neurodevelopment Alters Amino Acid Profile, Astrocyte Marker and Glutamatergic Excitotoxicity in the Rat Striatum.

There is a public health concern about the use of methylphenidate (MPH) since the higher prescription for young individuals and non-clinical purposes is addressed to the limited understanding of its neurochemical and psychiatric consequences. This study aimed to evaluate the impact of early and chronic MPH treatment on the striatum focusing on amino acid profile, glutamatergic excitotoxicity, redox status, neuroinflammation and glial cell responses. Male Wistar rats were treated with MPH (2.0 mg/kg) or saline solution from the 15th to the 44th postnatal day. Biochemical and histological analyses were conducted after the last administration. MPH altered the amino acid profile in the striatum, increasing glutamate and ornithine levels, while decreasing the levels of serine, phenylalanine, and branched-chain amino acids (leucine, valine, and isoleucine). Glutamate uptake and Na+,K+-ATPase activity were decreased in the striatum of MPH-treated rats as well as increased ATP levels, as indicator of glutamatergic excitotoxicity. Moreover, MPH caused lipid peroxidation and nitrative stress, increased TNF alpha expression, and induced high levels of astrocytes, and led to a decrease in BDNF levels. In summary, our results suggest that chronic early-age treatment with MPH induces parallel activation of damage-associated pathways in the striatum and increases its vulnerability during the juvenile period. In addition, data presented here contribute to shedding light on the mechanisms underlying MPH-induced striatal damage and its potential implications for neurodevelopmental disorders.

Correlation between compulsive behaviors and plastic changes in the dendritic spines of the prefrontal cortex and dorsolateral striatum of male rats.

Obsessive-compulsive disorder (OCD) is a mental affliction characterized by compulsive behaviors often manifested in intrusive thoughts and repetitive actions. The quinpirole model has been used with rats to replicate compulsive behaviors and study the neurophysiological processes associated with this pathology. Several changes in the dendritic spines of the medial prefrontal cortex (mPFC) and dorsolateral striatum (DLS) have been related to the occurrence of compulsive behaviors. Dendritic spines regulate excitatory synaptic contacts, and their morphology is associated with various brain pathologies. The present study was designed to correlate the occurrence of compulsive behaviors (generated by administering the drug quinpirole) with the morphology of the different types of dendritic spines in the mPFC and DLS. A total of 18 male rats were used. Half were assigned to the experimental group, the other half to the control group. The former received injections of quinpirole, while the latter rats were injected with physiological saline solution, for 10 days in both cases. After the experimental treatment, the quinpirole rats exhibited all the parameters indicative of compulsive behavior and a significant correlation with the density of stubby and wide neckless spines in both the mPFC and DLS. Dendritic spines from both mPFC and DLS neurons showed plastic changes correlatively with the expression of compulsive behavior induced by quinpirole. Further studies are suggested to evaluate the involvement of glutamatergic neurotransmission in the neurobiology of OCD.

Sustained fentanyl exposure inhibits neuronal activity in dissociated striatal neuronal-glial cocultures through actions independent of opioid receptors.

Besides having high potency and efficacy at the µ-opioid (MOR) and other opioid receptor types, fentanyl has some affinity for some adrenergic receptor types, which may underlie its unique pathophysiological differences from typical opioids. To better understand the unique actions of fentanyl, we assessed the extent to which fentanyl alters striatal medium spiny neuron (MSN) activity via opioid receptors or α1-adrenoceptors in dopamine type 1 or type 2 receptor (D1 or D2)-expressing MSNs. In neuronal and mixed-glial cocultures from the striatum, acute fentanyl (100 nM) exposure decreased the frequency of spontaneous action potentials. Overnight exposure of cocultures to 100 nM fentanyl severely reduced the proportion of MSNs with spontaneous action potentials, which was unaffected by coexposure to the opioid receptor antagonist naloxone (10 µM) but fully negated by coadministering the pan-α1-adrenoceptor inverse agonist prazosin (100 nM) and partially reversed by the selective α1A-adrenoceptor antagonist RS 100329 (300 nM). Acute fentanyl (100 nM) exposure modestly reduced the frequency of action potentials and caused firing rate adaptations in D2, but not D1, MSNs. Prolonged (2-5 h) fentanyl (100 nM) application dramatically attenuated firing rates in both D1 and D2 MSNs. To identify possible cellular sites of α1-adrenoceptor action, α1-adrenoceptors were localized in subpopulations of striatal astroglia and neurons by immunocytochemistry and Adra1a mRNA by in situ hybridization in astrocytes. Thus, sustained fentanyl exposure can inhibit striatal MSN activity via a nonopioid receptor-dependent pathway, which may be modulated via complex actions in α1-adrenoceptor-expressing striatal neurons and/or glia.NEW & NOTEWORTHY Acute fentanyl exposure attenuated the activity of striatal medium spiny neurons (MSNs) in vitro and in dopamine D2, but not D1, receptor-expressing MSNs in ex vivo slices. By contrast, sustained fentanyl exposure suppressed the spontaneous activity of MSNs cocultured with glia through a nonopioid receptor-dependent mechanism modulated, in part, by α1-adrenoceptors. Fentanyl exposure can affect striatal function via a nonopioid receptor mechanism of action that appears mediated by α1-adrenoreceptor-expressing striatal neurons and/or astroglia.

Region-Specific Gene Expression Changes Associated with Oleoylethanolamide-Induced Attenuation of Alcohol Self-Administration.

Oleoylethanolamide (OEA) is a lipid with anti-inflammatory activity that modulates multiple reward-related behaviors. Previous studies have shown that OEA treatment reduces alcohol self-administration (SA) while inhibiting alcohol-induced inflammatory signaling. Nevertheless, the specific mechanisms that OEA targets to achieve these effects have not been widely explored. Here, we tested the effects of OEA treatment during alcohol SA, extinction or previous to cue-induced reinstatement of alcohol seeking. In addition, we measured gene expression changes in the striatum and hippocampus of relevant receptors for alcohol consumption (Drd1, Drd2, Cnr1, Oprm) as well as immune-related proteins (Il-6, Il-1ß, Tlr4) and the brain-derived neurotrophic factor (Bdnf). Our results confirmed that when administered contingently, systemic OEA administration reduced alcohol SA and attenuated cue-induced reinstatement. Interestingly, we also observed that OEA treatment reduced the number of sessions needed for the extinction of alcohol seeking. Biochemical analyses showed that OEA induced gene expression changes in dopamine and cannabinoid receptors in the striatum and hippocampus. In addition, OEA treatment modulated the long-term immune response and increased Bdnf expression. These results suggest that boosting OEA levels may be an effective strategy for reducing alcohol SA and preventing relapse.

Volatile oil from Acori graminei Rhizoma affected the synaptic plasticity of rats with tic disorders by modulating dopaminergic and glutamatergic systems.

ETHNOPHARMACOLOGICAL RELEVANCE: Acori graminei Rhizoma is a commonly used traditional Chinese medicine for treating TD, with its main component being calamus volatile oil. Volatile Oil from Acori graminei Rhizoma (VOA)can protect nerve cells and alleviate learning and memory disorders. However, the mechanism of anti-tic of VOA is still unclear. AIM OF THE STUDY: We aimed to explore the effects of Volatile Oil from Acori Tatarinowii Rhizoma (VOA) on striatal dopaminergic and glutamatergic systems and synaptic plasticity of rats with Tic Disorder (TD), as well as its pharmaceutical mechanism against TD. MATERIALS AND METHODS: This study involved 48 (three-week-old) Sprague Dawley (SD) rats, which were randomly divided into two primary groups: Control (8) and TD (40). Rats in the TD group were injected intraperitoneally with 3,3-iminodipropionitrile (IDPN) to construct the TD rat model. They were divided into five subgroups: Model, Tiapride, VOA-high, VOA-medium, and VOA-low (N = 8). After modeling, VOA was administrated to rats in the VOA groups through gavage (once/day for four consecutive weeks), while rats in the blank control and model groups received normal saline of the same volume. The animals' behavioral changes were reflected using the stereotypic and motor behavior scores. After interferences, patterns of striatal neurons and the density of dendritic spines were investigated using H&E and Golgi staining, and the ultrastructure of striatal synapses was examined using Transmission Electron Microscopy (TEM). Furthermore, Ca2+ content was determined using the Ca2+ detector, and Dopamine (DA) and Glutamate (GLU) contents in serum and striatum were detected through ELISA. Finally, DRD1, DRD2, AMPAR1, NMPAR1, DAT, VMAT2, CAMKⅡ, and CREB expression in the striatum was detected using Quantitative real-time PCR (qRT-PCR), Western Blotting (WB) and Immunohistochemical (IHC) methods. RESULTS: Compared to rats in the blank control and model groups, rats in the VOA groups showed lower stereotypic behavior scores. Furthermore, rats in the VOA groups exhibited relieved, neuron damage and increased quantities of neuronal dendrites and dendritic spines Additionally, based on TEM images show that, the VOA groups showed a clear synaptic structure and increased amounts of postsynaptic dense substances and synaptic vesicles. The VOA groups also exhibited reduced Ca2+ contents, and upregulation of DRD1, DRD2, DAT, AMPAR1, and NMPAR1 and downregulation of VMAT-2, CAMKⅡ, and CREB in the striatum. CONCLUSIONS: In summary, VOA could influence synaptic plasticity by tuning the dopaminergic and glutamatergic systems, thus relieving TD.

Spontaneous Calcium Transients Recorded from Striatal Astrocytes in a Preclinical Model of Autism.

Autism spectrum disorder (ASD) is known as a group of neurodevelopmental conditions including stereotyped and repetitive behaviors, besides social and sensorimotor deficits. Anatomical and functional evidence indicates atypical maturation of the striatum. Astrocytes regulate the maturation and plasticity of synaptic circuits, and impaired calcium signaling is associated with repetitive behaviors and atypical social interaction. Spontaneous calcium transients (SCT) recorded in the striatal astrocytes of the rat were investigated in the preclinical model of ASD by prenatal exposure to valproic acid (VPA). Our results showed sensorimotor delay, augmented glial fibrillary acidic protein -a typical intermediate filament protein expressed by astrocytes- and diminished expression of GABAA-ρ3 through development, and increased frequency of SCT with a reduced latency that resulted in a diminished amplitude in the VPA model. The convulsant picrotoxin, a GABAA (γ-aminobutyric acid type A) receptor antagonist, reduced the frequency of SCT in both experimental groups but rescued this parameter to control levels in the preclinical ASD model. The amplitude and latency of SCT were decreased by picrotoxin in both experimental groups. Nipecotic acid, a GABA uptake inhibitor, reduced the mean amplitude only for the control group. Nevertheless, nipecotic acid increased the frequency but diminished the latency in both experimental groups. Thus, we conclude that striatal astrocytes exhibit SCT modulated by GABAA-mediated signaling, and prenatal exposure to VPA disturbs this tuning.

Silymarin ameliorates motor function and averts neuroinflammation-induced cell death in the rat model of Huntington's disease.

Huntington's disease (HD) is a scarce neurodegenerative disorder defined by chorea (unusual involuntary movements), behavioral presentations, psychiatric features, and cognitive deterioration. Although the precise pathogenic mechanism behind HD has not yet been identified, the most widely acknowledged pathways include excitotoxicity, mitochondrial malfunction, neuroinflammation, neurochemical imbalance, oxidative stress, and apoptosis HD has no efficient therapy. Current medications have drawbacks. Silymarin, a compound made up of standardized extracts obtained from the seeds of the Silybum marianum and polyphenolic flavonolignan, is utilized in therapeutic settings to treat a variety of experimental disorders in animals. Silymarin's key pharmacological activities include anti-cancer, hepatoprotection, antioxidant, cardioprotection, and anti-inflammatory. It also has no adverse side effects on people or animals. The current study aims to provide Silymarin's neuro-pharmacological activities or therapeutic qualities in HD. In this study, Thirty-six male Sprague-Dawley rats (200-220 g, 8 weeks) at the initial of the study were used. Silymarin solution (100 mg/Kg) was administered by oral gavage for 21 days to ameliorate neural damage in rats injected with 3-nitropropionicacid (3-NP) in a preliminary rat model of HD. The results showed that administration of silymarin to HD rats reduced gliosis, improved motor coordination and muscle activity, and increased striatal volume and the number of neurons and glial cells. Our results suggest that silymarin provides a protective environment for nerve cells and can have beneficial effects against the harmful effects of HD.