Injection Of Apomorphine Research Articles

Enhanced prepulse inhibition and low sensitivity to a dopamine agonist in HESR1 knockout mice

Transcription factor Hesr family genes are important in neuronal development. We demonstrated previously that HESR1 and HESR2 modified expression of the dopamine transporter (DAT) reporter gene. HESR-family genes have been investigated in development, but their functions, especially in relation to behaviors regulated by dopamine, in adult animals remain unclear. In the present study, we investigated the effects of Hesr1 and Hesr2 on behavior. A behavioral test battery to examine spontaneous activity, anxiety-like behavior, aggressive behavior, pain sensitivity, and sensorimotor gating was conducted in Hesr1 and Hesr2 knockout (KO) mice. Enhanced prepulse inhibition (PPI), which is a form of sensorimotor gating, was observed in only Hesr1 KO mice; other behavioral traits were mostly comparable to wild-type animals in both the Hesr1 and the Hesr2 KO lines. Next, we used a dopamine agonist, apomorphine, to confirm the involvement of the dopaminergic system. Injection of apomorphine reduced the enhanced PPI in Hesr1 KO mice. Additionally, dose-dependent sensitivity to the agonist was lower in the Hesr1 KO mice than in wild-type mice, suggesting that the enhanced PPI resulted from this alteration in dopamine sensitivity. Furthermore, DAT mRNA was downregulated in Hesr1 KO mice, whereas the dopamine D1 and D2 receptors were comparable. These findings suggest Hesr1 to be a novel factor that affects dopamine sensitivity and the sensorimotor gating system.

Neuroprotective Effects of Protocatechuic Aldehyde against Neurotoxin-Induced Cellular and Animal Models of Parkinson’s Disease

Protocatechuic aldehyde (PAL) has been reported to bind to DJ-1, a key protein involved in Parkinson’s disease (PD), and exerts potential neuroprotective effects via DJ-1 in SH-SY5Y cells. In this study, we investigated the neuroprotective pharmacological effects of PAL against neurotoxin-induced cell and animal models of PD. In cellular models of PD, PAL markedly increased cell viability rates, mitochondrial oxidation-reduction activity and mitochondrial membrane potential, and reduced intracellular ROS levels to prevent neurotoxicity in PC12 cells. In animal models of PD, PAL reduced the apomorphine injection, caused turning in 6-OHDA treated rats, and increased the motor coordination and stride decreases in MPTP treated mice. Meanwhile, in an MPTP mouse model, PAL prevented a decrease of the contents of dopamine (DA) and its metabolites in the striatum and TH-positive dopaminergic neuron loss in the substantia nigra (SN). In addition, PAL increased the protein expression of DJ-1 and reduced the level of α-synuclein in the SN of MPTP lesioned mice. PAL also increased the spine density in hippocampal CA1 neurons. The current study demonstrates that PAL can efficiently protect dopaminergic neurons against neurotoxin injury in vitro and in vivo, and that the potential mechanisms may be related to its effects in increasing DJ-1, decreasing α-synuclein and its growth-promoting effect on spine density.

Differential Interaction of Neuroleptics with Apomorphine-Induced Behavior in Rats as a Function of Changing Levels of Dopamine Receptor Stimulation

Twenty-two neuroleptic drugs were studied for interaction with the behavior induced by intravenous injection of apomorphine in rats. All compounds dose-dependently shortened the duration of the apomorphine-induced agitation and-with the exception of clozapine-shortened the onset of the de-arousal grooming that typically occurs immediately after the agitation phase has been terminated. Progressively higher doses were required to antagonize higher levels of apomorphine at earlier time intervals after the intravenous injection. The compounds also decreased palpebral opening, and most of them suppressed grooming behavior at higher doses. Compounds differed considerably in dose increments required for: 1) suppression of grooming, from 0.33 for clozapine to >600 for remoxipride, raclopride, and droperidol; 2) blockade of agitation at 5 minutes after apomorphine, from 2.6 for pimozide to 165 for chlorprothixene and 254 for remoxipride; 3) mild decrease of palpebral opening, from 0.21 for sertindole to 191 for remoxipride; and 4) pronounced decrease of palpebral opening, from 10 for melperone to >820 for raclopride. Only four compounds were able to advance grooming to 15 minutes postapomorphine, but again dose increments varied considerably: droperidol (3.4), pimozide (9.1), raclopride (42), and remoxipride (383). Based on these results obtained in a single animal model, compounds were differentiated in terms of behavioral specificity, incisiveness (the power to counteract the effects of progressively higher apomorphine concentrations), and sedative side-effect liability. Possible explanations for the observed differences and clinical relevance are discussed.

Radiotelemetric assessment of intracavernosal pressure in apomorphine-induced erection: hypercholesterolemic rats vs normal control

A recording of the intracavernosal pressure (ICP) in conscious rats using telemetry has the advantage of being able to evaluate erection under physiological conditions. The aim of this study was to determine whether the radiotelemetric assessment of ICP in apomorphine-induced erection is appropriate for assessing erectile function in an animal model of disease. Seven rats were assigned to the normal group, and another nine rats were assigned to the hypercholesterolemia group. A telemetric pressure sensor was implanted in the corpus cavernosum. Pressure was recorded in freely moving animals after apomorphine injection. Sexual events were visually identified and recorded. Only the pressure increase occurring during sexual behavior was analyzed. The main outcome measures were as follows: latency for first peak after injection (latency), duration, maximum ICP (Max ICP) and area under the curve (AUC). The mean latency, mean duration of each episode, mean Max ICP, mean AUC and mean summed AUC were 389.9 ± 59.4 s, 61.6 ± 7.8 s, 140.0 ± 22.5 mm Hg, 1834.4 ± 358.2 mm Hg s and 3259.1 ± 795.9 mm Hg s, respectively, for the normal group vs 652.8 ± 102.2 s, 32.4 ± 5.2 s, 92.7 ± 6.4 mm Hg, 572.9 ± 73.6 mm Hg s and 739.9 ± 87.2 mm Hg s, respectively, for the hypercholesterolemia group. There was a significant difference in mean latency, mean AUC and mean summed AUC. Additionally, we cannot find any obvious immediate adverse events after surgical implantation in both normal control and hypercholesterolemic rats. And, no catheter displacement and no adverse local reaction, including fibrosis to the implant, were observed. In conclusion, radiotelemetric assessment of ICP in apomorphine-induced erection provided consistent and accurate data during erectile events, and was appropriate for assessing erectile function in an animal model of disease.

The dopamine agonist apomorphine enhances conditioned pain modulation in healthy humans

Although cumulative evidence suggests that dopamine plays a role in pain processing, the mechanisms by which dopaminergic transmission affects pain remain elusive. Conditioned pain modulation (CPM) is a psychophysical paradigm based on endogenous descending inhibitory pain modulation. The current study was aimed to test the effects of apomorphine, a non-specific dopamine agonist, on the magnitude of CPM in healthy subjects. One hundred and five healthy subjects participated in this randomized, double-blind study. CPM was assessed by subtracting the response to a phasic painful heat stimulus administered simultaneously with a conditioning cold pain stimulus from the response to the same heat stimulus administered alone. CPM was tested prior to and 25min following a subcutaneous injection of either apomorphine (1.5mg) or a placebo. CPM following apomorphine administration increased by 27.3% and by only 4% following placebo administration. RM-ANOVA revealed a significant interaction between ‘session’ and ‘time’ factors (F=5.316, p=0.023, η=0.054), and significant effect for the ‘session’ (F=5.719, p=0.019, η=0.006), but not for the ‘time’ (F=0.586, p=0.446, η=0.057). These results suggest that dopaminergic pathways both participate in and enhance pain modulation, represented by CPM. The role of dopamine in pain processing should be further studied.

Characterization of Cognitive Deficits in Rats Overexpressing Human Alpha-Synuclein in the Ventral Tegmental Area and Medial Septum Using Recombinant Adeno-Associated Viral Vectors

Intraneuronal inclusions containing alpha-synuclein (a-syn) constitute one of the pathological hallmarks of Parkinson's disease (PD) and are accompanied by severe neurodegeneration of A9 dopaminergic neurons located in the substantia nigra. Although to a lesser extent, A10 dopaminergic neurons are also affected. Neurodegeneration of other neuronal populations, such as the cholinergic, serotonergic and noradrenergic cell groups, has also been documented in PD patients. Studies in human post-mortem PD brains and in rodent models suggest that deficits in cholinergic and dopaminergic systems may be associated with the cognitive impairment seen in this disease. Here, we investigated the consequences of targeted overexpression of a-syn in the mesocorticolimbic dopaminergic and septohippocampal cholinergic pathways. Rats were injected with recombinant adeno-associated viral vectors encoding for either human wild-type a-syn or green fluorescent protein (GFP) in the ventral tegmental area and the medial septum/vertical limb of the diagonal band of Broca, two regions rich in dopaminergic and cholinergic neurons, respectively. Histopathological analysis showed widespread insoluble a-syn positive inclusions in all major projections areas of the targeted nuclei, including the hippocampus, neocortex, nucleus accumbens and anteromedial striatum. In addition, the rats overexpressing human a-syn displayed an abnormal locomotor response to apomorphine injection and exhibited spatial learning and memory deficits in the Morris water maze task, in the absence of obvious spontaneous locomotor impairment. As losses in dopaminergic and cholinergic immunoreactivity in both the GFP and a-syn expressing animals were mild-to-moderate and did not differ from each other, the behavioral impairments seen in the a-syn overexpressing animals appear to be determined by the long term persisting neuropathology in the surviving neurons rather than by neurodegeneration.

The neurokinin-3 receptor (NK3R) antagonist SB222200 prevents the apomorphine-evoked surface but not nuclear NK3R redistribution in dopaminergic neurons of the rat ventral tegmental area

Schizophrenia is a severe condition that has been associated with functional abnormalities in dopaminergic (DA) neurons of the ventral tegmental area (VTA). Neurokinin-3 receptors (NK3Rs) of the tachykinin family of neuropeptides modulate the activity of VTA DA neurons and might be involved in DA abnormalities relevant to schizophrenia. Recent work from our lab showed that systemic injection of the dopamine D1/D2 receptor agonist apomorphine in rats, which mimics schizophrenia-like behaviors in humans, also evoked a redistribution of NK3Rs in DA neurons of the rat VTA. In the present study, VTA microinjection of the selective NK3R antagonist SB222200 (1nmol/0.2μl) or the nuclear import blocker SN50 (2μg/0.2μl) was performed in awake rats 10min prior to systemic injection of apomorphine. VTA sections were dual immunolabeled for the NK3R (immunogold) and the dopamine synthesizing enzyme tyrosine hydroxylase (TH, immunoperoxidase). Electron microscopic quantifications of somatic and dendritic densities of NK3 immunogold particles were compared in rats receiving central and systemic injections. In DA (TH-labeled) dendrites, VTA microinjection of SB222200 prevented the apomorphine-evoked decrease in surface NK3R density as well as the apomorphine-induced increase in cytoplasmic NK3R density. In contrast, VTA microinjection of SN50, but not SB222200, prevented the apomorphine-induced increase in nuclear NK3R density. VTA microinjection of SB222200 or SN50 without apomorphine had no effect on the NK3R distribution or density in TH and non-TH profiles within the VTA. In non-TH, presumably GABAergic neurons of the VTA, the NK3R densities in somata and dendrites were not significantly changed by apomorphine with or without SB222200. The results suggest that the NK3R antagonist SB222200 is effective against the apomorphine-evoked NK3R internalization in VTA DA dendrites, but does not prevent nuclear NK3R trafficking in VTA DA neurons. These results might have important implications in targeting NK3R antagonists in basic or clinical studies.

Effect of Pregabalin on Erectile Function and Penile NOS Expression in Rats with Streptozotocin-Induced Diabetes

To investigate the effect of pregabalin on erectile function and on the penile expression of nitric oxide synthase (NOS) isoforms in diabetic rat models. Male Sprague-Dawley rats were injected with streptozotocin to induce diabetes mellitus. The rats with blood glucose levels above 300 mg/dL were selected for the study. Those were randomly divided into 2 groups (N=10 per group): i) EDDM (erectile dysfunction diabetes mellitus) group fed with saline and ii) EDDM+Pregabalin treated group receiving pregabalin (10 mg/k/day) by intragastric administration. 10 animals served as a control group and received no streptozotocin. 4 weeks later, the erectile function of the rats was assessed by recording frequency of erection after subcutaneous apomorphine (80 ug/kg) injection. Superoxide anion generation and the expression of mRNA of nNOS and eNOS were evaluated in corpora cavernosum tissue. Penile erection, the expression of both nNOS, eNOS and superoxide generation were significantly decreased in pregabalin treated group compared to control group. Treatment with pregabalin for 4 weeks decreases superoxide production but cannot improve erectile dysfunction in diabetic rats probably by inhibiting Ca(2)(+) channel-mediated NOS activation.

Behavioural recovery on simple and complex tasks by means of cell replacement therapy in unilateral 6‐hydroxydopamine‐lesioned mice

Before cell replacement therapies can enter the clinic, it is imperative to test the therapeutic benefits in well-described animal models. In the present study, we aimed to investigate the effects of 6-hydroxydopamine lesions to the medial forebrain bundle and subsequent grafting of embryonic day (E)12.5 ventral mesencephalon into the denervated striatum in C57/Bl6 mice on a battery of simple motor tests (drug-induced rotation, rotarod, and corridor) and the lateralised choice reaction time task conducted in the mouse nine-hole box. Histological analysis confirmed effective lesions and good graft survival. The lesion induced marked deficits in the choice reaction time task, the rotarod test, and corridor test, and these deficits were partially but significantly alleviated in the grafted mice. Although the lesions induced significant rotation following injections of amphetamine and apomorphine, respectively, the grafts did not, suprisingly, alleviate the rotation deficit. This study shows the ability of ventral mesencephalic tissue to ameliorate some of the lesion-induced deficits, and the power of operant testing in detecting small but significant improvements. The behavioural tests presented are useful drug-free approaches for evaluating cell-based therapies.

Effects of dopamine receptor agonist and antagonists on cholestasis-induced anxiolytic-like behaviors in rats

Dysfunctions in the dopamine transmission system have been suggested to contribute to the pathogenesis of hepatic encephalopathy. In an experimental animal model, cholestasis induction through bile duct ligation may present several main pathological features of hepatic encephalopathy. Dopaminergic systems are shown to play pivotal roles in regulation of anxiety-like behaviors. The main bile duct in male Wistar rats, weighing 220–240g, was ligated using two ligatures plus duct transection in between. Anxiety-like behaviors were measured using the elevated plus maze task. Cholestasis increased the open arm time percentage (%OAT), 13 but not 10 days after bile duct ligation, indicating an anxiolytic-like effect. Sole intraperitoneal injection of apomorphine (dopamine D1/D2 receptor agonist, 0.25mg/kg), SCH23390 (dopamine D1 receptor antagonist, 0.005, 0.01 and 0.02mg/kg) or sulpiride (dopamine D2 receptor antagonist, 0.125, 0.25 and 0.5mg/kg) did not alter %OAT, open arm entries percentage (%OAE) and locomotor activity in the sham-operated rats. Meanwhile, the higher dose apomorphine (0.5mg/kg) induced anxiolytic-like behaviors in this group. The subthreshold dose injection of SCH23390 or sulpiride, partially reversed the anxiolytic-like behaviors induced by cholestasis (13 days after bile duct ligation). On the other hand, subthreshold dose of apomorphine in cholestatic rats (10 days post bile duct ligation) induced anxiolytic-like effects which could be blocked by SCH23390 or sulpiride. The effective doses of above drugs did not alter locomotor activity, number of rearings, groomings and defections. These findings suggested that the dopaminergic system may potentially be involved in the modulation of cholestasis-induced anxiolytic-like behaviors in rats.

Turmeric active substance, curcumin, enhanced apomorphine-induced yawning in rats.

Curcumin is a major constituent of turmeric and influences many functions of the brain. In the present study, we investigated the effect of curcumin on yawning induced by apomorphine in rats. Curcumin administered orally for 10 consecutive days. Yawning was induced by subcutaneous (s.c.) injection of apomorphine (a dopamine receptor agonist) and the number of yawns was recorded for a period of 30 min. Apomorphine (0.05 and 0.1 mg/kg) produced yawning. Haloperidol (a dopamine receptors antagonist) at a dose of 0.05 mg/kg partially and at a dose of 0.2 mg/kg completely inhibited apomorphine-induced yawning. Curcumin alone produced no yawning, whereas at doses of 30 and 60 mg/kg, it increased yawning induced by 0.1 mg/kg of apomorphine. Curcumin at the high doses (30 and 60 mg/kg) produced yawning when apomorphine (0.1 mg/kg) action was partially blocked with 0.5 mg/kg of haloperidol. In the presence of complete blockade of apomorphine (0.1 mg/kg) action with 0.2 mg/kg of haloperidol, curcumin did not produce yawning. The results showed that curcumin at high doses increased apomorphine-induced yawning. In the presence of partial, but not complete blockade of apomorphine action, curcumin produced yawning. Curcumin produced a dopamine-like effect on yawning.

アポモルヒネ皮下注射製剤（販売名：アポカイン<sup>®</sup>皮下注30 mg）―レボドパ治療に伴う運動症状の日内変動に対するレスキュー療法―

パーキンソン病（PD）はアルツハイマー病に次いで患者数が多い慢性進行性の神経変性疾患である．レボドパ製剤はPDの運動機能障害に対して最も強力な改善効果を示すが，長期間の使用により運動症状の日内変動が大きくなり，薬効持続時間の短縮や突発的かつ予測困難な薬効減弱等のオフ症状が増加する．オフ症状の発現は患者のQOLを著しく低下させることから適切な対処が必要であるが，進行期のPD患者では，他のPD治療薬の追加・併用やレボドパの用量・用法の最適化の後もオフ症状が残存することがある．この残存したオフ症状に対しては，症状が発現した時に即効的に症状を改善するレスキュー療法が有用と考えられる．アポモルヒネはドパミンD1およびD2受容体サブファミリーに対して幅広く作動活性を有しており，PD患者の線条体においてドパミン受容体を介して間接経路出力および直接経路出力の両方を調節することにより，抗PD作用を示すと考えられる．霊長類の病態モデル動物および進行期のPD患者において，皮下投与したアポモルヒネはレボドパと遜色ない強い薬効を示す．またアポモルヒネ製剤は，顕著な薬効，即効性および作用時間が比較的短いこと等から，既存のPD治療薬によりコントロールできないオフ症状に対するレスキュー治療薬として，欧米各国で長い臨床使用の実績がある．アポモルヒネの薬理作用として嘔吐中枢の刺激による悪心・嘔吐等の発現が知られているが，これらの副作用は制吐剤の適切な使用等により制御可能である．レスキュー用途には，患者が必要と感じた時に患者自らが決められた薬物量を安全かつ確実に投与できることが重要となる．そのため，本邦においては，アポモルヒネの皮下投与のための専用の電動式インジェクターが開発された．本剤は内服薬に反応しない重篤なオフ症状に対するアンメットニーズを充たす新しいタイプのPD治療薬であり，本邦においては2012年3月に「パーキンソン病におけるオフ症状の改善（レボドパ含有製剤の頻回投与及び他の抗パーキンソン病薬の増量等を行っても十分に効果が得られない場合）」を効能・効果として承認された．海外と同様に本邦においても，本剤が患者とその家族および介護者のQOLに貢献することが期待される．

Morning Akinesia and the Potential Role of Gastroparesis – Managing Delayed Onset of First Daily Dose of Oral Levodopa in Patients with Parkinson’s Disease

In patients with Parkinson’s disease (PD), motor and non-motor symptoms are frequent during OFF periods, especially when the next levodopa dose has a delayed onset of action (delayed ON). Delayed ON of the first daily dose of levodopa is known as morning akinesia, which can significantly affect quality of life and impair daily activities. Morning akinesia can occur due to a delay in gastric emptying, impaired intestinal absorption, pharmacodynamic effects or other mechanisms. Gastroparesis is common in patients with PD and can cause gastrointestinal symptoms, delayed ON and morning akinesia. Alternative delivery of dopaminergic therapy by a non-oral route may be useful in patients with PD and gastroparesis. Subcutaneous apomorphine injection is used by patients with PD in the OFF state to decrease time-to-ON. An ongoing study is investigating its use for morning akinesia, as well as the frequency of delayed gastric emptying in these patients.

Monitoring of Erectile and Urethral Sphincter Dysfunctions in a Rat Model Mimicking Radical Prostatectomy Damage

Animal models of urinary incontinence and erectile dysfunction following radical prostatectomy (RP) are lacking. To develop an animal model of combined post-RP urethral sphincter and erectile dysfunctions, and noninvasive methods to assess erectile function (EF) and urinary sphincter function (USF) during prolonged follow-up. In the main experiments, 60 male Sprague Dawley rats were randomized to a sham operation (N = 30) or electrocautery of both sides of the striated urethral sphincter (N = 30). EF and USF were evaluated preoperatively and on postoperative days 7, 15, 30, 60, and 90. Sphincter and penile tissue samples were evaluated histologically on days 7 (N = 10) and 30 (N = 10) to detect apoptosis (TUNEL assays) and fibrosis (Trichrome Masson staining). To assess EF, we measured systemic and penile blood flow using penile laser Doppler and penile rigidity using a durometer before and after apomorphine injection. USF was assessed based on the retrograde leak point pressure (LPPr). Apomorphine increased baseline Doppler flow by 180% (95% confidence interval, 156-202%) and penile hardness from 3.49 ± 0.5 to 7.16 ± 0.82 Shore A units but did not change systemic arterial flow. Mean LPPr was 76.8 ± 6.18 mm Hg at baseline and decreased by 50% after injury, with no response to apomorphine on day 7. EF and USF impairments persisted up to 90 days post injury. Histology showed penile apoptosis on day 7 and extensive urethral sphincter and penile fibrosis on day 30. Our data did not allow us to determine whether the impairment in erectile response to apomorphine preponderantly reflected arterial penile insufficiency or veno-occlusive dysfunction. Electrocautery of the striated urethral sphincter caused severe and lasting impairment of EF and USF that could be monitored repeatedly using minimally invasive methods. This new animal model may hold potential for developing new treatments designed to correct post-RP impairments.

Antipsychotic-like activity of Noni (Morinda citrifolia Linn.) in mice

BackgroundNoni fruit is widely consumed in tropical regions of Indonesia to the Hawaiian Islands. The noni plant has a long history of use as a medicinal plant to treat a wide variety of ailments including CNS disorders. The present investigation was designed to evaluate the antipsychotic effect of noni fruits (Morinda citrifolia Linn.) using mouse models of apomorphine-induced climbing behaviour and methamphetamine-induced stereotypy (licking, biting, gnawing and sniffing).MethodsIn acute study, the methanolic extract of Morinda citrifolia (MMC) at different doses 1, 3, 5, 10 g/kg was administered orally one hour prior to apomorphine (5 mg/kg, i.p) and methamphetamine ( 5 mg/kg, i.p) injection respectively in Swiss albino mice. In chronic studies, (TAHITIAN NONI® Juice, TNJ) was made available freely in daily drinking water at 30, 50 and 100% v/v for 7 days; 30 and 50% v/v for 21 days respectively. On the test day, an equivalent average daily divided dose of TNJ was administered by oral gavage one hour prior to apomorphine treatment. Immediately after apomorphine/ methamphetamine administration, the animals were placed in the cylindrical metal cages and observed for climbing behaviour/ stereotypy and climbing time.ResultsThe acute treatment of MMC (1, 3, 5, 10 g/kg, p.o) significantly decreased the apomorphine-induced cage climbing behaviour and climbing time in mice in a dose dependent manner. The MMC also significantly inhibited methamphetamine-induced stereotypy behaviour and climbing time in mice dose-dependently. The 7 and 21 days treatment of TNJ in drinking water at 50 and 100%v/v significantly alleviated the apomorphine-induced climbing behaviour and climbing time in mice.ConclusionsThe present study results demonstrated the antidopaminergic effect of Morinda citrifolia Linn. in mice, suggesting that noni has antipsychotic-like activity which can be utilized in the treatment of psychiatric disorders. However further studies are warranted to identify the active principles responsible for the antipsychotic activity of noni.

Increased Dopamine Receptor Activity in the Nucleus Accumbens Shell Ameliorates Anxiety during Drug Withdrawal

A number of lines of evidence suggest that negative emotional symptoms of withdrawal involve reduced activity in the mesolimbic dopamine system. This study examined the contribution of dopaminergic signaling in structures downstream of the ventral tegmental area to withdrawal from acute morphine exposure, measured as potentiation of the acoustic startle reflex. Systemic administration of the general dopamine receptor agonist apomorphine or a cocktail of the D1-like receptor agonist SKF82958 and the D2-like receptor agonist quinpirole attenuated potentiated startle during morphine withdrawal. This effect was replicated by apomorphine infusion into the nucleus accumbens shell. Finally, apomorphine injection was shown to relieve startle potentiation during nicotine withdrawal and conditioned place aversion to morphine withdrawal. These results suggest that transient activation of the ventral tegmental area mesolimbic dopamine system triggers the expression of anxiety and aversion during withdrawal from multiple classes of abused drugs.

Effects of Ningdong granule on DA, DRD2, and HVA in a rat model of Tourette's syndrome

ObjectiveNingdong granule is a traditional Chinese medicine preparation for the treatment of Tourette's syndrome. MethodsSixty-four rats were randomly assigned to a control group and three experimental groups, respectively. Rat models of Tourette's syndrome were established via intraperitoneal injection of apomorphine (Apo). The rats in the experimental groups were subsequently intragastrically injected with haloperidol at 10 mg/kg (haloperidol group), Ningdong granule at 370 mg/kg (NDG group), and normal saline (0.9%) at 10 mL/kg (Apo group), respectively. Rat behaviors were observed and recorded on a daily basis. After 12 w, all rats were sacrificed, and sera and striatal tissues were harvested. Homovanillic acid levels in sera, as well as dopamine and dopamine D2 receptor mRNA expression in the striatum, were measured to determine possible mechanisms of Ningdong granule on the dopamine system in a rat model of Tourette's syndrome. ResultsFollowing intervention, stereotype actions of the Tourette's syndrome rats were significantly inhibited in the haloperidol and NDG groups, respectively (P<0.01). Homovanillic levels were significantly greater in the haloperidol and NDG groups, respectively (P<0.05). In addition, dopamine levels were significantly less in the NDG group (P<0.01), and DRD2 mRNA expression was significantly reduced in the haloperidol and NDG groups, respectively (P<0.05). ConclusionResults demonstrated that Ningdong granule effectively inhibited stereotype actions and Tourette's syndrome symptoms by promoting dopamine metabolism, reducing dopamine levels in the striatum, increasing homovanillic acid content in sera, and reducing mRNA expression of DRD2 in the striatum.

Characterization of corpus cavernosum smooth muscle cell phenotype in diabetic rats with erectile dysfunction

Phenotypic modulation from a contractile to a proliferative state within vascular smooth muscle cells has a critical role in the pathogenesis of a variety of cardiovascular diseases. To investigate the characterization of corpus cavernosum smooth muscle cell phenotype in diabetic rats with erectile dysfunction, a group of Sprague-Dawley rats (n=30) were induced by intraperitoneal injection of streptozotocin (60 mg kg(-1)) and screened by subcutaneous injection of apomorphine (100 μg kg(-1)) for the measurement and comparison of the penile erections, and then three different groups were defined. Primary corpus cavernosum smooth muscle cells were cultured and passaged. The cavernous tissue segments were subjected to quantitative real-time polymerase chain reaction to determine the expressions of smooth muscle α-actin (SMA), SM myosin heavy chain (SMMHC), smoothelin, calponin and myocardin. Cell contractility in vitro and western blot analysis of SMA and SMMHC in the cavernous tissues and cells were determined. Compared with the control group (n=8) and the diabetes mellitus group (n=5), the expressions of SMA, calponin, SMMHC, smoothelin and myocardin mRNA were decreased in the cavernous tissues in rats of the diabetic erectile dysfunction group (n=15; P=0.001 and 0.02, P=0.014 and 0.012, both P<0.001, P=0.005 and <0.001, P=0.003 and 0.035, respectively). The levels of SMA and SMMHC proteins showed a significant decrease in cavernous tissues and cultured cells in rats of the diabetic erectile dysfunction group. Cells of the diabetic erectile dysfunction group exhibited significantly less contractility compared with those of other groups (P<0.001). Corpus cavernosum SM cell possesses the ability to modulate the phenotype under hyperglycemic conditions, which could have a key role in the pathogenesis of diabetic erectile dysfunction.

Combinatorial topography and cell-type specific regulation of the ERK pathway by dopaminergic agonists in the mouse striatum

Therapeutic agents and drugs of abuse regulate the extracellular signal-regulated kinase (ERK) cascade signaling in the medium-sized spiny neurons (MSNs) of the striatum. However, whether this regulation is associated with specific cortical and thalamic inputs has never been studied. We used Drd2-EGFP BAC-transgenic mice to undertake a topographical and cell-type specific analysis of ERK phosphorylation and two of its downstream targets histone H3 and ribosomal protein S6 (rS6) in the dorsal striatum following injection of SKF81297 (D1R-like agonist), quinpirole (D2R-like agonist) or apomorphine (non selective DA receptor agonist). In striatal areas receiving inputs from the cingulate/prelimbic, visual and auditory cortex, SKF81297 treatment increased phosphorylation of ERK, histone H3 and rS6 selectively in EGFP-negative MSNs of Drd2-EGFP mice. In contrast, no regulation was found in striatal region predominantly targeted by the sensorimotor and motor cortex. Apomorphine slightly enhanced ERK and rS6, but not histone H3 phosphorylation. This regulation occurred exclusively in EGFP-negative neurons mostly in striatal sectors receiving connections from the insular, visual and auditory cortex. Quinpirole administration inhibited basal ERK activation but did not change histone H3 and rS6 phosphorylation throughout the rostrocaudal axis of the dorsal striatum. This anatomo-functional study indicates that D1R and D2R agonists produce a unique topography and cell-type specific regulation of the ERK cascade signaling in the mouse striatum, and that those patterns are closely associated with particular cortical and thalamic inputs. This work evidences the need of a precise identification of the striatal areas under study to further understand striatal plasticity.

Deep brain stimulation of the subthalamic nucleus in the 6-hydroxydopamine rat model of Parkinson's disease: Effects on sensorimotor gating

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is effectively used to treat motor symptoms in Parkinson's disease (PD). Recently more attention has been paid to behavioral disturbances caused by PD itself and by STN DBS. In the 6-hydroxydopamine (6-OHDA) PD rat model we investigated the effect of STN DBS on deficient prepulse inhibition (PPI) induced by the dopamine (DA) receptor agonist apomorphine, which is an operative measure for disturbed sensorimotor gating seen in certain neuropsychiatric disturbances.Male Sprague Dawley rats with bilateral lesions of the nigrostriatal DA system (striatal injection of 6-OHDA or vehicle for sham-lesion) were bilaterally implanted with electrodes for DBS into the STN. After determination of individual thresholds rats were stimulated (130Hz, 80μs pulse width) or sham-stimulated for epochs of six days. On the sixth day of each epoch rats were tested for PPI of the acoustic startle response after apomorphine or vehicle injection in a within randomized cross-over design.Stimulation of the STN improved PPI in vehicle-treated (control) rats, but deteriorated PPI after apomorphine treatment. This effect was more pronounced in sham-lesioned rats. Furthermore, in lesioned rats the startle reaction was marginally enhanced without effect of stimulation or apomorphine treatment.These data suggest that STN DBS interacts with dopaminergic action. With respect to functional neurosurgery, STN DBS alone may improve certain aspects of psychiatric disturbances, but may have a different impact when combined with dopaminergic medication.