Dopamine And 3,4-dihydroxyphenylacetic Acid Research Articles

Early-life exposure to sex hormones promotes voluntary ethanol intake in adulthood. A vulnerability factor to drug addiction.

While there is extensive research on alcohol dependence, the factors that make an individual vulnerable to developing alcoholism haven't been explored much. In this study, we aim to investigate how neonatal exposure to sex hormones affects alcohol intake and the regulation of the mesolimbic pathway in adulthood.The study aimed to investigate the impact of neonatal exposure to a single dose of testosterone propionate (TP) or estradiol valerate (EV) on ethanol consumption in adult rats. The rats were subjected to a two-bottle free-choice paradigm, and the content of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens (NAcc) was measured using HPLC-ED. The expression of critical DA-related proteins in the mesolimbic pathway was evaluated through RT-qPCR and western blot analysis.Supraphysiological neonatal exposure to EV or TP resulted in increased ethanol intake over four weeks in adulthood. In addition, the DA and DOPAC content was reduced and increased in the NAcc of EV and TP-treated rats, and β-endorphin content in the hypothalamus decreased in EV-treated rats. The VTA μ receptor and DA type 2 form short receptor (D2S) expression were significantly reduced in EV and TP male rats. Finally, in an extended 6-week protocol, the increase in ethanol consumption induced by EV was mitigated during the initial two hours post-naloxone injection.Neonatal exposure to sex hormones is a detrimental stimulus for the brain, which can facilitate the development of addictive behaviors, including alcohol use disorder.

Response of nitrergic system in the brain of rat conditioned to intracranial self-stimulation.

The role of nitrergic system in modulating the action of psychostimulants on reward processing is well established. However, the relevant anatomical underpinnings and scope of the involved interactions with mesolimbic dopaminergic system have not been clarified. Using immunohistochemistry, we track the changes in neuronal nitric oxide synthase (nNOS) containing cell groups in the animals conditioned to intracranial self-stimulation (ICSS) via an electrode implanted in the lateral hypothalamus-medial forebrain bundle (LH-MFB) area. An increase in the nNOS immunoreactivity was noticed in the cells and fibers in the ventral tegmental area (VTA) and nucleus accumbens shell (AcbSh), the primary loci of the reward system. In addition, nNOS was up-regulated in the nucleus accumbens core (AcbC), vertical limb of diagonal band (VDB), locus coeruleus (LC), lateral hypothalamus (LH), superficial gray layer (SuG) of the superior colliculus, and periaqueductal gray (PAG). The brain tissue fragments drawn from these areas showed a change in nNOS mRNA expression, but in opposite direction. Intracerebroventricular (icv) administration of nNOS inhibitor, 7-nitroindazole (7-NI) showed decreased lever press activity in a dose-dependent manner in ICSS task. While an increase in the dopamine (DA) and 3, 4-dihydroxyphenylacetic acid (DOPAC) efflux was noted in the microdialysates collected from the AcbSh of ICSS rats, pre-administration of 7-NI (icv route) attenuated the response. The study identifies nitrergic centers that probably mediate sensory, cognitive, and motor components of the goal-directed behavior.

Improvement effect of cinnamaldehyde on reserpine-induced Parkinson's disease rat model

In order to study the neuroprotective mechanism of cinnamaldehyde on reserpine-induced Parkinson's disease(PD) rat models, 72 male Wistar rats were randomly divided into blank group, model group, Madopar group, and cinnamaldehyde high-, medium-, and low-dose groups. Except for the blank group, the other groups were intraperitoneally injected with reserpine of 0.1 mg·kg~(-1) once every other morning, and cinnamaldehyde and Madopar solutions were gavaged every afternoon. Open field test, rotarod test, and oral chewing movement evaluation were carried out in the experiment. The brain was taken and fixed. The positive expression of dopamine receptor D1(DRD1) was detected by TSA, and the changes in neurotransmitters such as dopamine(DA) and 3,4-dihydroxyphenylacetic acid(DOPAC) in the brain were detected by enzyme-linked immunosorbent assay(ELISA). The protein and mRNA expression levels of tyrosine hydroxylase(TH) and α-synuclein(α-Syn) in substantia nigra(SN) were detected by RT-PCR and Western blot. The results showed that after the injection of reserpine, the hair color of the model group became yellow and dirty; the arrest behavior was weakened, and the body weight was reduced. The spontaneous movement and exploration behavior were reduced, and the coordination exercise ability was decreased. The number of oral chewing was increased, but the cognitive ability was decreased, and the proportion of DRD1 positive expression area in SN was decreased. The expression of TH protein and mRNA was down-regulated, and that of α-Syn protein and mRNA was up-regulated. After cinnamaldehyde intervention, it had an obvious curative effect on PD model animals. The spontaneous movement behavior, the time of staying in the rod, the time of movement, the distance of movement, and the number of standing times increased, and the number of oral chewing decreased. The proportion of DRD1 positive expression area in SN increased, and the protein and mRNA expression levels of α-Syn were down-regulated. The protein and mRNA expression levels of TH were up-regulated. In addition, the levels of DA, DOPAC, and homovanillic acid(HVA) neurotransmitters in the brain were up-regulated. This study can provide a new experimental basis for clinical treatment and prevention of PD.

Myopia control in Mendelian forms of myopia.

To study the effectiveness of high-dose atropine for reducing eye growth in Mendelian myopia in children and mice. We studied the effect of high-dose atropine in children with progressive myopia with and without a monogenetic cause. Children were matched for age and axial length (AL) in their first year of treatment. We considered annual AL progression rate as the outcome and compared rates with percentile charts of an untreated general population. We treated C57BL/6J mice featuring the myopic phenotype of Donnai-Barrow syndrome by selective inactivation of Lrp2 knock out (KO) and control mice (CTRL) daily with 1% atropine in the left eye and saline in the right eye, from postnatal days 30-56. Ocular biometry was measured using spectral-domain optical coherence tomography. Retinal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured using high-performance liquid chromatography. Children with a Mendelian form of myopia had average baseline spherical equivalent (SE) -7.6± 2.5D and AL 25.8± 0.3 mm; children with non-Mendelian myopia had average SE -7.3± 2.9 D and AL 25.6± 0.9 mm. During atropine treatment, the annual AL progression rate was 0.37 ± 0.08 and 0.39 ± 0.05 mm in the Mendelian myopes and non-Mendelian myopes, respectively. Compared with progression rates of untreated general population (0.47 mm/year), atropine reduced AL progression with 27% in Mendelian myopes and 23% in non-Mendelian myopes. Atropine significantly reduced AL growth in both KO and CTRL mice (male, KO: -40 ± 15; CTRL: -42 ± 10; female, KO: -53 ± 15; CTRL: -62 ± 3μm). The DA and DOPAC levels 2 and 24 h after atropine treatment were slightly, albeit non-significantly, elevated. High-dose atropine had the same effect on AL in high myopic children with and without a known monogenetic cause. In mice featuring a severe form of Mendelian myopia, atropine reduced AL progression. This suggests that atropine can reduce myopia progression even in the presence of a strong monogenic driver.

Recovery of dopaminergic amacrine cells after strobe light stimulation in the developing rat retina

Concerns regarding the impact of strobe light on human health and life have recently been raised. Sources of strobe light include visual display terminals, light-emitting diodes, and computer monitors. Strobe light exposure leads to visual discomfort, headaches, and poor visual performance and affects the number of dopaminergic amacrine cells (DACs) in the developing retina, as well as retinal dopamine levels in animals. DACs serve as the sole source of retinal dopamine, and dopamine release from the retina is activated by light exposure following a circadian rhythm. Using a Sprague-Dawley rat model, this study sought to determine whether changes in DACs caused by strobe light are recoverable after ceasing strobe light exposure during retinal development. From eye opening (postnatal 2 weeks), rats in the control group were reared under normal light (an unflickering 150 lux incandescent lamp with a 12 h light/dark cycle), whereas those in the experimental group (i.e., strobe-recovery group) were reared under strobe light (2 Hz for 12 h/day) exposure for 2 weeks. After postnatal week 4, normal light was provided to all animals to observe the reversibility of the effect of strobe light. Immunohistochemistry and immunoblot analysis for the rate limiting enzyme for dopamine synthesis, tyrosine hydroxylase (TH), as well as high-pressure liquid chromatography for measuring dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) were performed at postnatal weeks 4, 6, 8, and 10. The number of type I and type II TH-immunoreactive (TH-IR) cells across the entire retina was counted to evaluate whether changes in DACs induced by strobe light could recover after ceasing strobe light exposure. The number of type I TH-IR cells slightly decreased but remained at a constant level in the control group. In contrast, the number of type I TH-IR cells rapidly decreased up to postnatal week 6, but then increased after postnatal week 8 in the strobe-recovery group. Subsequently, the number of type I TH-IR cells eventually reached a number similar to that in the control group. In addition, the number of intermediate-sized TH-IR cells were increased at postnatal weeks 8 and 10 and the dopamine level was decreased at postnatal week 8 in the strobe-recovery group. However, the levels of DOPAC and TH proteins did not differ between the two groups. This suggests that changes in DACs caused by strobe light are reversible and that type II TH-IR cells may play a key role in this recovery.

Studies on the interactions of retinal dopamine with choroidal thickness in the chicken

PurposeRecently, an increasing number of studies relied on the assumption that visually induced changes in choroidal thickness can serve as a proxy to predict future axial eye growth. The retinal signals controlling choroidal thickness are, however, not well defined. We have studied the potential roles of dopamine, released from the retina, in the choroidal response in the chicken.MethodsChanges in retinal dopamine release and choroidal thickness changes were induced by intravitreal injections of either atropine (250 µg or 360 nMol), atropine combined with a dopamine antagonist, spiperone (500 µMol), or spiperone alone and were tracked by optical coherence tomography (OCT). To visually stimulate dopamine release, other chicks were exposed to flicker light of 1, 10, or 400 Hz (duty cycle 0.2) and choroidal thickness was tracked. In all experiments, dopamine and 3,4-Dihydroxyphenylacetic acid (DOPAC) were measured in vitreous, retina, and choroid by high-performance liquid chromatography with electrochemical detection (HLPC-ED). The distribution of the rate-limiting enzyme of dopamine synthesis, tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), vascular endothelial growth factor (VEGF), and alpha2A adrenoreceptors (alpha2A-ADR) was studied in the choroid by immunofluorescence.ResultsThe choroid thickened strongly in atropine-injected eyes, less so in atropine + spiperone–injected eyes and became thinner over the day in spiperone alone-, vehicle-, or non-injected eyes. Flickering light at 20 lx, both 1 and 10 Hz, prevented diurnal choroidal thinning, compared to 400 Hz, and stimulated retinal dopamine release. Correlation analysis showed that the higher retinal dopamine levels or release, the thicker became the choroid. TH-, nNOS-, VEGF-, and alpha2A adrenoreceptor–positive nerve fibers were localized in the choroid around lacunae and in the walls of blood vessels with colocalization of TH and nNOS, and TH and VEGF.ConclusionsRetinal DOPAC and dopamine levels were positively correlated with choroidal thickness. TH-positive nerve fibers in the choroid were closely associated with peptides known to play a role in myopia development. Findings are in line with the hypothesis that dopamine is related to retinal signals controlling choroidal thickness.

Early-Life Exposure to Non-Absorbable Broad-Spectrum Antibiotics Affects the Dopamine Mesocorticolimbic Pathway of Adult Rats in a Sex-Dependent Manner.

Gut microbiota with a stable, rich, and diverse composition is associated with adequate postnatal brain development. Colonization of the infant’s gut begins at birth when parturition exposes the newborn to a set of maternal bacteria, increasing richness and diversity until one to two first years of age when a microbiota composition is stable until old age. Conversely, alterations in gut microbiota by diet, stress, infection, and antibiotic exposure have been associated with several pathologies, including metabolic and neuropsychiatric diseases such as obesity, anxiety, depression, and drug addiction, among others. However, the consequences of early-life exposure to antibiotics (ELEA) on the dopamine (DA) mesocorticolimbic circuit are poorly studied. In this context, we administered oral non-absorbable broad-spectrum antibiotics to pregnant Sprague-Dawley dams during the perinatal period (from embryonic day 18 until postnatal day 7) and investigated their adult offspring (postnatal day 60) to assess methylphenidate-induced conditioned place preference (CPP) and locomotor activity, DA release, DA and 3,4-dihydroxyphenylacetic acid (DOPAC) content in ventral tegmental area (VTA), and expression of key proteins within the mesocorticolimbic system. Our results show that ELEA affect the rats conduct by increasing drug-seeking behavior and locomotor activity induced by methylphenidate of males and females, respectively, while reducing dopamine striatal release and VTA content of DOPAC in females. In addition, antibiotics increased protein levels of DA type 1 receptor in prefrontal cortex and VTA of female rats, and tyrosine hydroxylase in VTA of adult male and female rats. Altogether, these results suggest that ELEA alters the development of the microbiota-gut-brain axis affecting the reward system and the response to abuse drugs in adulthood.

Neuroplastic Changes in the Superior Colliculus and Hippocampus in Self-rewarding Paradigm: Importance of Visual Cues.

Coincident excitation via different sensory modalities encoding objects of positive salience is known to facilitate learning and memory. With a view to dissect the contribution of visual cues in inducing adaptive neural changes, we monitored the lever press activity of a rat conditioned to self-administer sweet food pellets in the presence/absence of light cues. Application of light cues facilitated learning and consolidation of long-term memory. The superior colliculus (SC) of rats trained on light cue showed increased neuronal activity, dendritic branching, and brain-derived neurotrophic factor (BDNF) protein and mRNA expression. Concomitantly, the hippocampus showed augmented neurogenesis as well as BDNF protein and mRNA expression. While intra-SC administration of U0126 (inhibitor of ERK 1/2 and long-term memory) impaired memory formation, lidocaine (local anaesthetic) hindered memory recall. The light cue-dependent sweet food pellet self-administration was coupled with increased efflux of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens shell (AcbSh). In conditioned rats, pharmacological inhibition of glutamatergic signalling in dentate gyrus (DG) reduced lever press activity, as well as DA and DOPAC secretion in the AcbSh. We suggest that the neuroplastic changes in the SC and hippocampus might represent memory engrams sculpted by visual cues encoding reward information.

Voluntary oral dosing for precise experimental compound delivery in adult rats.

Preclinical drug studies routinely administer experimental compounds to animal models with the goal of minimizing potential adverse events from the procedure. In this study, we assessed the ability to train adult male Long Evans rats to accept daily voluntarily syringe feedings of l-3,4-dihydroxyphenylalanine (L-DOPA) compared to intraperitoneal (IP) injections. Rats were trained to become familiar with the syringe and then fed a training solution that did not contain the experimental compound. If the rat was compliant during the training phase, the dilution of training solution was continuously decreased and replaced with the experimental solution. Voluntary oral dosing compliance was recorded and quantified throughout the study. To assess drug activity within the drug-targeted tissues, the striatum and retina were collected and analyzed for L-DOPA, dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) levels by high performance liquid chromatography (HPLC). Drug delivery efficiency by oral dosing was directly compared to IP injection by collecting plasma and analyzing L-DOPA levels with HPLC. Adult male rats had high compliance for voluntary oral dosing. HPLC showed that oral administration of the compound at the same dose as IP injection yielded significantly lower plasma levels, and that higher oral L-DOPA doses yield higher plasma L-DOPA content. This study describes detailed methodology to train adult rats to syringe feed experimental compounds and provides important preclinical research on drug dosing and drug delivery to the striatum and retina.

Neuropeptide CART modulates dopamine turnover in the nucleus accumbens: Insights into the anatomy of rewarding circuits.

Neuropeptide cocaine- and amphetamine-regulated transcript (CART) is known to influence the activity of the canonical mesolimbic dopaminergic pathway and modulate reward seeking behaviour. CART neurons of the lateral hypothalamus (LH) send afferents to the ventral tegmental area (VTA) and paraventricular thalamic nucleus (PVT) and these nuclei, in turn, send secondary projections to nucleus accumbens. We try to dissect the precise sites of CART's action in these circuits in promoting reward. Rats were implanted with bipolar electrode targeted at the lateral hypothalamus-medial forebrain bundle (LH-MFB) and trained to press the lever through intracranial self-stimulation (ICSS) protocol. CART (55-102) administered directly into posterior VTA (pVTA) or PVT of the conditioned rats significantly increased the number of lever presses, indicating reward-promoting activity of the peptide. Concomitant increase in dopamine (DA) and 3, 4-dihydroxyphenylacetic acid (DOPAC) efflux was noted in the microdialysate collected from the nucleus accumbens shell (AcbSh). On the other hand, immunoneutralization of endogenous CART with CART antibodies injected directly in the pVTA or PVT reduced the lever press activity as well as DA and DOPAC efflux in the AcbSh. Injection of CART (1-39) in pVTA or PVT was ineffective. We suggest that CART cells in the LH-MFB area send afferents to (a) pVTA and influence dopaminergic neurons projecting to AcbSh and (b) PVT, from where the secondary neurons may feed into the AcbSh. Excitation of the CARTergic pathway to the pVTA as well as the PVT seems to promote DA release in the AcbSh and contribute to the generation of reward.

Neuroprotective effects of pomegranate (Punica granatum L.) juice and seed extract in paraquat-induced mouse model of Parkinson\u2019s disease

BackgroundParaquat, (PQ), an herbicide that can induce Parkinsonian-like symptoms in rodents and humans. The consumption of phytochemical-rich plants can reduce the risk of chronic illnesses such as inflammation and neurodegenerative diseases. The present study aimed to investigate the protective effects of pomegranate seed extract (PSE) and juice (PJ) against PQ-induced neurotoxicity in mice.MethodsMice were assigned into 4 groups; three groups received PQ (10 mg/kg, i.p.) twice a week for 3 weeks. Two of the PQ-induced groups pretreated with either PSE or PJ. Detection of phytochemicals, total phenolics, and total flavonoids in PSE and PJ was performed. Tyrosine hydroxylase (TH) level was measured in the substantia nigra (SN) by Western blotting technique. Striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were detected using high-performance liquid chromatography (HPLC). The levels of adenosine triphosphate (ATP), malondialdehyde (MDA), and the activity of the antioxidant enzymes were estimated in the striatum by colorimetric analysis. Striatal pro-inflammatory and anti-inflammatory markers using enzyme-linked immunosorbent assay (ELISA) as well as DNA fragmentation degree by qualitative DNA fragmentation assay, were evaluated. Real-time polymerase chain reaction (qPCR) assay was performed for the detection of nuclear factor kappa B (NF-кB) gene expression. Moreover, Western blotting analysis was used for the estimation of the cluster of differentiation 11b (CD11b), transforming growth factor β (TGF-β), and glial cell-derived neurotrophic factor (GDNF) levels in the striatum.ResultsPretreatment with PSE or PJ increased the levels of TH in the SN as well as DA and its metabolite in the striatum that were reduced by PQ injection. PSE and PJ preadministration improved the PQ-induced oxidative stress via a significant reduction of the MDA level and the augmentation of antioxidant enzyme activities. PSE and PJ also significantly downregulated the striatal NF-кB gene expression, reduced the PQ-enhanced apoptosis, decreased the levels of; pro-inflammatory cytokines, CD11b, and TGF-β coupled with a significant increase of; interleukin-10 (IL-10), GDNF, and ATP levels as compared with PQ-treated mice.ConclusionsThe current study indicated that PSE and PJ consumption may exhibit protective effects against PQ-induced neurotoxicity in mice.

Initiation of L-DOPA Treatment After Detection of Diabetes-Induced Retinal Dysfunction Reverses Retinopathy and Provides Neuroprotection in Rats

PurposeL-DOPA treatment initiated at the start of hyperglycemia preserves retinal and visual function in diabetic rats. Here, we investigated a more clinically relevant treatment strategy in which retinal and visual dysfunction designated the beginning of the therapeutic window for L-DOPA treatment.MethodsSpatial frequency thresholds using optomotor response and oscillatory potential (OP) delays using electroretinograms were compared at baseline, 3, 6, and 10 weeks after streptozotocin (STZ) between diabetic and control rats. L-DOPA/carbidopa treatment (DOPA) or vehicle was delivered orally 5 days per week beginning at 3 weeks after STZ, when significant retinal and visual deficits were measured. At 10 weeks after STZ, retinas were collected to measure L-DOPA, dopamine, and 3,4-dihydroxyphenylacetic acid (DOPAC) levels using high-performance liquid chromatography.ResultsSpatial frequency thresholds decreased at 6 weeks in diabetic vehicle rats (28%), whereas diabetic DOPA rats had stable thresholds (<1%) that maintained to 10 weeks, creating significantly higher thresholds compared with diabetic vehicle rats (P < 0.0001). OP2 implicit times in response to dim, rod-driven stimuli were decreased in diabetic compared with control rats (3 weeks, P < 0.0001; 10 weeks, P < 0.01). With L-DOPA treatment, OP2 implicit times recovered in diabetic rats to be indistinguishable from control rats by 10 weeks after STZ. Rats treated with L-DOPA showed significantly increased retinal L-DOPA (P < 0.001) and dopamine levels (P < 0.05).ConclusionsL-DOPA treatment started after the detection of retinal and visual dysfunction showed protective effects in diabetic rats.Translational RelevanceEarly retinal functional deficits induced by diabetes can be used to identify an earlier therapeutic window for L-DOPA treatment which protects from further vision loss and restores retinal function.

Administration of a VIP-antagonist in vivo modifies ovarian hormone secretion in a rat model with polycystic ovary syndrome

AimsIn the cyclic rat in estrus, the vasoactive intestinal peptide (VIP) has an impact on ovarian function, which depends on the endocrine status of the animal. In this work, we aimed to clarify the participation of VIP in the pathophysiological condition of polycystic ovary syndrome (PCOS) using a model of PCOS induced by estradiol valerate (EV-PCOS) in rats. Main methodsIn the cyclic rat in estrus and in the EV-PCOS model, we analyzed the acute effects of blocking VIP receptors with the use of an antagonist (Ant-VIP) injected into the left or right ovarian bursa on the steroidogenic response and ovarian catecholamine levels. Key findingsIn the cyclic animal in estrus, the treatment with Ant-VIP in the left ovarian bursa resulted in a reduction in testosterone serum levels and in ovarian levels of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC), without changes in 4-hydroxy-3-methoxyphenyl (MHPG) and norepinephrine (NE). When the treatment was applied on the right side, only MHPG levels increased.In the EV-PCOS model, the treatment with Ant-VIP in the left ovarian bursa increased testosterone, estradiol, MHPG, and NE levels. When the treatment was performed on the right side, progesterone levels decreased and estradiol increased, without changes in ovarian catecholamines. SignificanceThe binding of VIP to its receptors differentially regulates steroidogenesis in the cyclic animal in estrus and in the EV-PCOS model. The blocking of VIP signaling produces changes in ovarian catecholamines.

β-Methylphenylalanine exerts neuroprotective effects in a Parkinson's disease model by protecting against tyrosine hydroxylase depletion.

We evaluated the neuroprotective effects of β‐methylphenylalanine in an experimental model of rotenone‐induced Parkinson's disease (PD) in SH‐SY5Y cells and rats. Cells were pre‐treated with rotenone (2.5 µg/mL) for 24 hours followed by β‐methylphenylalanine (1, 10 and 100 mg/L) for 72 hours. Cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), mitochondrial fragmentation, apoptosis, and mRNA and protein levels of tyrosine hydroxylase were determined. In a rat model of PD, dopamine (DA) and 3,4‐dihydroxyphenylacetic acid (DOPAC) levels, bradykinesia and tyrosine hydroxylase expression were determined. In rotenone–pre‐treated cells, β‐methylphenylalanine significantly increased cell viability and MMP, whereas ROS levels, apoptosis and fragmented mitochondria were reduced. β‐Methylphenylalanine significantly increased the mRNA and protein levels of tyrosine hydroxylase in SH‐SY5Y cells. In the rotenone‐induced rat model of PD, oral administration of β‐methylphenylalanine recovered DA and DOPAC levels and bradykinesia. β‐Methylphenylalanine significantly increased the protein expression of tyrosine hydroxylase in the striatum and substantia nigra of rats. In addition, in silico molecular docking confirmed binding between tyrosine hydroxylase and β‐methylphenylalanine. Our experimental results show neuroprotective effects of β‐methylphenylalanine via the recovery of mitochondrial damage and protection against the depletion of tyrosine hydroxylase. We propose that β‐methylphenylalanine may be useful in the treatment of PD.

Reduced dopaminergic tone during lactation is permissive to the hypothalamic stimulus for suckling-induced prolactin release.

Dopamine from tuberoinfundibular dopaminergic (TIDA) neurones tonically inhibits prolactin (PRL) secretion. Lactational hyperprolactinaemia is associated with a reduced activity of TIDA neurones. However, it remains controversial whether the suckling-induced PRL surge is driven by an additional decrease in dopamine release or by stimulation from a PRL-releasing factor. In the present study, we further investigated the role of dopamine in the PRL response to suckling. Non-lactating (N-Lac), lactating 4hour apart from pups (Lac), Lac with pups return and suckling (Lac+S), and post-lactating (P-Lac) rats were evaluated. PRL levels were elevated in Lac rats and increased linearly within 30 minutes of suckling in Lac+S rats. During the rise in PRL levels, dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the median eminence (ME) and neurointermediate lobe of the pituitary did not differ between Lac+S and Lac rats. However, dopamine and DOPAC were equally decreased in Lac and Lac+S compared to N-Lac and P-Lac rats. Suckling, in turn, reduced phosphorylation of tyrosine hydroxylase in the ME of Lac+S. Domperidone and bromocriptine were used to block and activate pituitary dopamine D2 receptors, respectively. Domperidone increased PRL secretion in both N-Lac and Lac rats, and suckling elicited a robust surge of PRL over the high basal levels in domperidone-treated Lac+S rats. Conversely, bromocriptine blocked the PRL response to suckling. The findings obtained in the present study provide evidence that dopamine synthesis and release are tonically reduced during lactation, whereas dopamine is still functional with respect to inhibiting PRL secretion. However, there appears to be no further reduction in dopamine release associated with the suckling-induced rise in PRL. Instead, the lower dopaminergic tone during lactation appears to be required to sensitise the pituitary to a suckling-induced PRL-releasing factor.

Behavioral and neurochemical characterization of the spontaneous mutation tremor, a new mouse model of audiogenic seizures

The tremor mutant phenotype results from an autosomal recessive spontaneous mutation arisen in a Swiss–Webster mouse colony. The mutant mice displayed normal development until three weeks of age when they began to present motor impairment comprised by whole body tremor, ataxia, and decreased exploratory behavior. These features increased in severity with aging suggesting a neurodegenerative profile. In parallel, they showed audiogenic generalized clonic seizures. Results from genetic mapping identified the mutation tremor on chromosome 14, in an interval of 5 cM between D14Mit37 (33.21 cM) and D14Mit115 (38.21 cM), making Early Growth Response 3 (Egr3) the main candidate gene. Comparing with wild type (WT) mice, the tremor mice showed higher hippocampal gene expression of Egr3 and Gabra1 and increased concentrations of noradrenalin (NOR; p = .0012), serotonin (5HT; p = .0083), 5-hydroxyindoleacetic acid (5-HIAA; p = .0032), γ-amino butyric acid (GABA; p = .0123), glutamate (p = .0217) and aspartate (p = .0124). In opposition, the content of glycine (p = .0168) and the vanillylmandelic acid (VMA)/NOR ratio (p = .032) were decreased. Regarding to dopaminergic system, neither dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) contents nor the turnover rate of DA showed statistically significant differences between WT and mutant mice. Data demonstrated that audiogenic seizures of tremor mice are associated with progressive motor impairment as well as to hippocampal alterations of the Egr3 and Gabra1 gene expression and amino acid and monoamine content. In addition, the tremor mice could be useful for study of neurotransmission pathways as modulators of epilepsy and the pathogenesis of epilepsies occurring with generalized clonic seizures.

Stimulatory effect of dopamine derivative, salsolinol, on pulsatile luteinizing hormone secretion in seasonally anestrous sheep: Focus on dopamine, kisspeptin and gonadotropin-releasing hormone

In the present study, there was testing of the hypothesis that a centrally administered dopamine (DA) derivative, salsolinol, could affect pulsatile luteinizing hormone (LH) secretion in seasonally anestrous sheep by affecting the neuronal components of the estradiol (E2) negative feedback. In two experiments performed during early spring (increasing day length – March/April), salsolinol or Ringer-Locke solution (control) were administered into the third brain ventricle (IIIv): 1) in several injections for three consecutive days; and 2) in several hour-long infusions. In addition to determining the LH concentration (in both experiments), the abundances of gonadotropin-releasing hormone (GnRH) and kisspeptin mRNA were examined in the hypothalamus and LHβ subunit mRNA in the pituitary (Experiment 1). In Experiment 2, concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined in perfusates collected from the infundibular nucleus/median eminence (IN/ME) by the push-pull method. In both experiments, salsolinol increased both LH pulse frequency (P < 0.05) and plasma LH concentration (P < 0.001) compared to controls. The injected salsolinol also increased (P < 0.05) the abundance of GnRH mRNA in the mediobasal hypothalamus and kisspeptin mRNA in the arcuate nucleus. The two doses of infused salsolinol decreased DA to undetectable concentrations and DOPAC concentration by 60% in perfusates collected from the IN/ME. In conclusion, exogenous salsolinol functioning centrally stimulates pulsatile LH secretion in sheep during seasonal anestrus. It is suggested that salsolinol may have this effect by reducing the activity of the hypothalamic neuroendocrine dopaminergic system, which results in an increase in both kisspeptin and GnRH neurons activity.

Determination of endogenous substance change in PM2.5-induced rat plasma and lung samples by UPLC-MS/MS method to identify potential markers for lung impairment.

Exposure to fine particulate matter (PM2.5) could induce lung impairment aggravation. Moreover, endogenous substances are known to play a significant role in lung impairment. Therefore, the research objectives was to investigate the influence of PM2.5-induced lung impairment on the levels of the eight endogenous substances, γ-aminobutyric acid (GABA), acetylcholine (ACh), glutamate (Glu), serotonin (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), noradrenaline (NE), dopamine (DA), and 3, 4-dihydroxyphenylacetic acid (DOPAC). A sensitive UPLC-MS/MS method for the simultaneous determination of these endogenous substances in rat plasma and lung tissues was developed. The validated method was successfully applied for comparing profiles of analytes in rat plasma and lung tissues. The results indicated that five endogenous substances, namely, GABA, Ach, Glu, DA, and DOPAC, had a significant change in the rats with PM2.5-induced lung impairment.

Neuroprotective effect of diclofenac on chlorpromazine induced catalepsy in rats.

Neuroinflammation plays a key role in progressive degeneration of dopaminergic cells. Upregulation of prostaglandins and free radicals formation are involved in the mechanisms of cell death in Parkinson's disease (PD). The present study aimed to investigate the neuroprotective effect of diclofenac against chlorpromazine (CPZ) induced catalepsy and motor impairment in mice. Adult Wistar rats treated with CPZ (3mg/kg/day, IP) were orally dosed with diclofenac and L-dopa/carbidopa for 21days. Catalepsy was measured after 21days of dosing by using standard bar test at 30, 60, 90, 120 and 180min then motor performances were assessed via open field test and wire hanging test. Histopathological investigation and determination of dopamine (DA) and 3,4-Dihydroxyphenylacetic acid (DOPAC) levels of rat's brain was also carried out. We found that CPZ treated group exhibited reduced motor impairment after 21days of treatment in open field and wire hanging test (P < 0.01) as compared to control group. The cataleptic scores of CPZ treated rats were also significantly increased (P < 0.01) after 21days of chronic dosing, however diclofenac treated groups showed significant reduction in cataleptic scores with improved motor performances. Histopathology of CPZ treated rats showed marked degeneration with architecture distortion in the mid brain region. Dopaminergic degeneration is confirmed by neurochemical results that showed reduced amount of dopamine and DOPAC levels in mid brain. Moreover, histopathological slides of diclofenac treated rats showed improved architecture with reduced gliosis of mid brain region as well as improved dopamine and DOPAC levels were achieved after 21days dosing of diclofenac. Taken together, the present work provide an evidence that diclofenac ameliorated behavioral performances by mediating neuroprotection against CPZ induced PD via preventing dopaminergic neuronal cell death.

Selective changes in locomotor activity in mice due to low-intensity microwaves amplitude modulated in the EEG spectral domain

Despite the numerous benefits of microwave applications in our daily life, microwaves were associated with diverse neurological complaints such as headaches and impaired sleep patterns, and changes in the electroencephalogram (EEG). To which extent microwaves influence the brain function remains unclear. This exploratory study assessed the behavior and neurochemistry in mice immediately or 4weeks after a 6-day exposure to low-intensity 10-GHz microwaves with an amplitude modulation (AM) of 2 or 8Hz. These modulation frequencies of 2 and 8Hz are situated within the delta and theta-alpha frequency bands in the EEG spectrum and are associated with sleep and active behavior, respectively. During these experiments, the specific absorbance rate was 0.3W/kg increasing the brain temperature with 0.23°C. For the first time, exposing mice to 8-Hz AM significantly reduced locomotor activity in an open field immediately after exposure which normalized after 4weeks. This in contrast to 2-Hz AM which didn’t induce significant changes in locomotor activity immediately and 4weeks after exposure. Despite this difference in motor behavior, no significant changes in striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels and DOPAC/DA turnover nor in cortical glutamate (GLU) concentrations were detected. In all cases, no effects on motor coordination on a rotarod, spatial working memory, anxiety nor depressive-like behavior were observed. The outcome of this study indicates that exposing mice to low-intensity 8-Hz AM microwaves can alter the locomotor activity in contrast to 2-Hz AM which did not affect the tested behaviors.