Possible involvement of the dopamine D2 receptors of ventromedial hypothalamus in the control of free- and scheduled-feeding and plasma ghrelin level in rat.

OBJECTIVES: We investigated effect of the ventromedial hypothalamus (VMH) dopamine D2 receptor inhibition on food intake and plasma ghrelin following chronic free or scheduled meal with different caloric intakes. METHODS: Male Wistar rats (220-250 g) were fed diets containing free (control) or three scheduled diets of standard, restricted and high-fat for 1 month. The animals stereotaxically received an intra VMH single dose of sulpiride (0.005 µg)/or saline (0.5 µL) before meal time. Thirty minutes later, food intake and circulating ghrelin were measured. RESULTS: Sulpiride significantly reduced food intake and ghrelin concentration in freely fed and scheduled-standard diet (p<0.05), while increased food intake, with ghrelin level on fasted level in scheduled-restricted group (p<0.01) compared to control. Food intake and ghrelin concentration between scheduled-high fat and freely fed or scheduled-standard diets did not show significant changes. CONCLUSIONS: The VMH D2 receptors are possibly involved in controlling scheduled eating behavior, depending on energy balance context.

A novel nasal co-loaded loratadine and sulpiride nanoemulsion with improved downregulation of TNF-α, TGF-ß and IL-1 in rabbit models of ovalbumin-induced allergic rhinitis.

PURPOSE: The work aimed to develop a co-loaded loratadine and sulpiride nasal nanoemulsion for allergic rhinitis management. METHODS: Compatibility studies were conducted adopting differential scanning calorimetry and Fourier transform infrared spectroscopy. Nanoemulsion formulations were prepared using soybean lecithin, olive oil and tween 80. Sodium cholate and glycerol were employed as co-surfactants. Nanoemulsions were assessed for viscosity, pH, droplet size, polydispersity index, zeta potential, electrical conductivity, entrapment, In vitro drug release and corresponding kinetics. Stability of the selected formulation was investigated. The biological effectiveness was evaluated in rabbit models of ovalbumin-induced allergic rhinitis by measuring TNF-α, TGF-ß and IL-1. RESULTS: Compatibility studies revealed absence of drug/drug interactions. Nanoemulsions exhibited > 90% entrapment efficiency. The selected nanoemulsion demonstrated small droplet size (85.2 ± 0.2 nm), low PDI (0.35 ± 0.0) and appropriate Zeta Potential (-23.3 ± 0.2) and stability. It also displayed enhanced in vitro drug release following the Higuashi Diffusion and Baker-Lonsdale models. The mean relative mRNA expression of TNF-α, IL-1 and TGF-ß significantly decreased from 9.59 ± 1.06, 4.15 ± 0.02 and 4.15 ± 0.02 to 1.28 ± 0.02, 1.93 ± 0.06 and 1.56 ± 0.02 respectively after treatment with the selected nanoemulsion formulation. CONCLUSION: The results reflected a promising potent effect of the combined loratadine and sulpiride nasal nanoemulsion in managing the symptoms of allergic rhinitis.

Chemical Composition of Essential Oil from Flower of 'Shanzhizi' (Gardenia jasminoides Ellis) and Involvement of Serotonergic System in Its Anxiolytic Effect.

Gardenia jasminoides Ellis is a famous fragrant flower in China. Previous pharmacological research mainly focuses on its fruit. In this study, the essential oil of the flower of 'Shanzhizi', which was a major variety for traditional Chinese medicine use, was extracted by hydro distillation and analyzed by GC-MS. Mouse anxiety models included open field, elevated plus maze (EPM), and light and dark box (LDB), which were used to evaluate its anxiolytic effect via inhalation. The involvement of monoamine system was studied by pretreatment with neurotransmitter receptor antagonists WAY100635, flumazenil and sulpiride. The monoamine neurotransmitters contents in the prefrontal cortex (PFC) and hippocampus after aroma inhalation were also analyzed. The results showed that inhalation of G. jasminoides essential oil could significantly elevated the time and entries into open arms in EPM tests and the time explored in the light chamber in LDB tests with no sedative effect. WAY100635 and sulpiride, but not flumazenil, blocked its anxiolytic effect. Inhalation of G. jasminoides essential oil significantly down-regulated the 5-HIAA/5-HT in the PFC and reduced the 5-HIAA content in hippocampus compared to the control treatment. In conclusion, inhalation of gardenia essential oil showed an anxiolytic effect in mice. Monoamine, especially the serotonergic system, was involved in its anxiolytic effect.

Investigation of Antidepressant, Anxiolytic and Sedative Activities of the Aqueous Leaf Extract of Musa sapientum Linn. (Banana; Musaceae).

BACKGROUND: Musa sapientum Linn. (Musaceae) is used in traditional African medicine in the management of mental disorders. This study was conducted to evaluate the central nervous system activities of the aqueous leaf extract of M. sapientum (MS). MATERIALS AND METHODS: MS (50, 100 and 200 mg/kg, p.o.) was administered to separate groups of mice 1 h before behavioural studies. The antidepressant effect was studied using the forced swimming test (FST) and tail suspension test (TST) while the elevated plus maze (EPM) and the hole-board tests were used to evaluate the anxiolytic effect. The probable mechanism of antidepressant-like effect was also investigated. RESULTS: MS (50, 100 and 200 mg/kg) produced significant (P<0.0001) reduction in the duration of immobility with peak effect at 200 mg/kg (79.6%) in FST and 66.9 % in TST respectively when compared with control. The pre-treatment of mice with prazosin (α1-adrenoceptor antagonist, 62.5 µg/kg, i.p.) and sulpiride (dopamine D2 receptor antagonist, 50 mg/kg, i.p.) significantly prevented the antidepressant effect produced by MS in FST. However, pre-treatment of mice with metergoline (5-HT2 receptor antagonist, 4 mg/kg, i.p.) and yohimbine (α2-adrenoceptor antagonist, 1 mg/kg, i.p.) did not prevent the antidepressant effect of MS. In the EPM test, MS did not significantly increase open arm exploration. It also did not significantly increase the number of head dips in the hole-board test. CONCLUSIONS: Results showed that MS had antidepressant activity possibly mediated through α1-adrenergic and D2 dopaminergic receptors, without significant anxiolytic effect.

The influence of dopaminergic system inhibition on biosynthesis of gonadotrophin-releasing hormone (GnRH) and GnRH receptor in anoestrous sheep; hierarchical role of kisspeptin and RFamide-related peptide-3 (RFRP-3).

This study aimed to explain how prolonged inhibition of central dopaminergic activity affects the cellular processes governing gonadotrophin-releasing hormone (GnRH) and LH secretion in anoestrous sheep. For this purpose, the study included two experimental approaches: first, we investigated the effect of infusion of sulpiride, a dopaminergic D2 receptor antagonist (D2R), on GnRH and GnRH receptor (GnRHR) biosynthesis in the hypothalamus and on GnRHR in the anterior pituitary using an immunoassay. This analysis was supplemented by analysis of plasma LH levels by radioimmunoassay. Second, we used real-time polymerase chain reaction to analyse the influence of sulpiride on the levels of kisspeptin (Kiss1) mRNA in the preoptic area and ventromedial hypothalamus including arcuate nucleus (VMH/ARC), and RFamide-related peptide-3 (RFRP-3) mRNA in the paraventricular nucleus (PVN) and dorsomedial hypothalamic nucleus. Sulpiride significantly increased plasma LH concentration and the levels of GnRH and GnRHR in the hypothalamic-pituitary unit. The abolition of dopaminergic activity resulted in a significant increase in transcript level of Kiss1 in VMH/ARC and a decrease of RFRP-3 in PVN. The study demonstrates that dopaminergic neurotransmission through D2R is involved in the regulatory pathways of GnRH and GnRHR biosynthesis in the hypothalamic-pituitary unit of anoestrous sheep, conceivably via mechanisms in which Kiss1 and RFRP-3 participate.

Influence of sulpiride treatment on the level of prolactin and immunoglobulins in the peripheral blood of mares during the postpartum period.

The aim of this study was to determine the effect of increased levels of prolactin (PRL) on the concentration of immunoglobulins in the blood, colostrum and milk of mares. The study was conducted on 12 mares of the Polish Pony breed (6 in the control and 6 in the experimental group). To induce hyperprolactinaemia in mares of the experimental group, 750 mg sulpiride was administered orally once a day. The initial PRL concentration was 52.22 ± 11.21 ng/ml in the control group and 49.39 ± 10.12 ng/ml in the experimental group. In the subsequent days, the concentration of PRL dynamically changed. Statistical analysis showed highly significant differences (P < 0.01) between the groups. The concentration of immunoglobulins in the blood plasma was at the same level during the experimental period (32.97-29.08 mg/ml in the experimental group and 28.60-18.11 mg/ml in the control group). Statistical analysis showed highly significant differences between the groups in blood plasma immunoglobulin level (P < 0.01). The highest immunoglobulin concentration was obtained within 12 h after parturition in the control and the experimental group (23.49 ± 2.12 mg/ml and 26.94 ±1.72 mg/ml, respectively). The lowest values were obtained on day 12 after parturition in the experimental group (10.15 mg/ml ± 1.47 mg/ml) and on day 7 after parturition in the control group (14.30 mg/ml ± 2.48 mg/ml). In conclusion, this study did not provide evidence that the lactogenic hormone prolactin is involved in the transfer of immunoglobulins into the colostrum in horses.

Sulpiride, Amisulpride, Thioridazine, and Olanzapine: Interaction with Model Membranes. Thermodynamic and Structural Aspects.

Neuroleptic drugs are widely applied in effective treatment of schizophrenia and related disorders. The lipophilic character of neuroleptics means that they tend to accumulate in the lipid membranes, impacting their functioning and processing. In this paper, the effect of four drugs, namely, thioridazine, olanzapine, sulpiride, and amisulpride, on neutral and negatively charged lipid bilayers was examined. The interaction of neuroleptics with lipids and the subsequent changes in the membrane physical properties was assessed using several complementary biophysical approaches (isothermal titration calorimetry, electron paramagnetic resonance spectroscopy, dynamic light scattering, and ζ potential measurements). We have determined the thermodynamic parameters, that is, the enthalpy of interaction and the binding constant, to describe the interactions of the investigated drugs with model membranes. Unlike thioridazine and olanzapine, which bind to both neutral and negatively charged membranes, amisulpride interacts with only the negatively charged one, while sulpiride does not bind to any of them. The mechanism of olanzapine and thioridazine insertion into the bilayer membrane cannot be described merely by a simple molecule partition between two different phases (the aqueous and the lipid phase). We have estimated the number of protons transferred in the course of drug binding to determine which of its forms, ionized or neutral, binds more strongly to the membrane. Finally, electron paramagnetic resonance results indicated that the drugs are localized near the water-membrane interface of the bilayer and presence of a negative charge promotes their burying deeper into the membrane.

Nucleus accumbens dopamine receptors mediate hypothalamus-induced antinociception in the rat formalin test.

BACKGROUND: Lateral hypothalamus (LH) involves in modulation of tonic pain. Regarding the direct and indirect neural connections between the LH and nucleus accumbens (NAc), we aimed to examine the pain modulatory role of NAc dopamine receptors in modulation of LH-induced analgesia in the formalin test. METHODS: Vehicle-control groups received saline or DMSO into the NAc and saline into the LH. Carbachol-control groups received carbachol (250 nmol/L) into the LH, 5 min after saline or DMSO injection into the NAc. In treatment groups, intra-NAc administration of SCH-23390 or sulpiride (D1-and D2-like dopamine receptor antagonists, respectively) was performed 5 min before carbachol injection. Formalin test was done in all rats 5 min after the second injection. RESULTS: The blockade of NAc dopamine receptors reduced carbachol-induced antinociception during both phases of formalin test and reduction in LH-induced analgesia during the late phase was more than that during the early phase. Furthermore, contribution of D2-like dopamine receptors to mediation of anti-hyperalgesic effect of carbachol was greater than that of D1-like dopamine receptors during the late phase. CONCLUSIONS: The findings suggest that LH-VTA-NAc circuit is contributed to the modulation of formalin-induced pain. These findings demonstrate that transmission at D1- and D2-like dopamine receptors mediates the LH-induced analgesia. SIGNIFICANCE: Blockade of accumbal dopamine receptors attenuated analgesia induced by carbachol injection into the lateral hypothalamus during both phases of formalin test. Effect of blockade of D1- and D2-like dopamine receptors on reduction in antinociception was more during the late phase. Contribution of D2-like dopamine receptors to mediation of antinociception during the late phase was greater than the early phase.

Serotonergic and dopaminergic systems are implicated in antidepressant-like effects of chotosan, a Kampo formula, in mice.

We previously demonstrated that chotosan (CTS), a traditional herbal formula called Kampo medicine, improves diabetes-induced cognitive deficits. In the present study, we investigated the antidepressant-like effects of CTS in mice. The administration of CTS (1.0 g/kg, for 3 days) decreased the immobility time in the forced-swim test, and this decrease was prevented by the prior administration of sulpiride (an antagonist of D2/3 receptors) and WAY100635 (an antagonist of 5-HT1A receptors). None of the treatments tested altered the locomotor activity of mice. These results suggest that CTS exerts antidepressant-like effects through changes in the serotonergic and dopaminergic systems.

Formulation, characterization, in vitro and in vivo evaluation of castor oil based self-nano emulsifying levosulpiride delivery systems.

CONTEXT: Levosulpiride (LSP) is a hydrophobic benzamide derivative used in the treatment of schizophrenia. SNEDDS were extensively practiced for systemic delivery of poorly aqueous soluble drugs to achieve maximum bioavailability. OBJECTIVE: The present study was focussed on the formulation, optimisation and evaluation of LSP SNEDDS using castor oil, for enhancement of drug absorption and bioavailability. MATERIALS AND METHODS: Pseudo-ternary phase diagram was plotted to identify the range of SNEDDS components. Twenty formulations were designed, prepared and characterised by its particle size, zeta potential, viscosity, and stability. In vitro dissolution data modelling was performed. Microscopy, FTIR and in vivo bioavailability studies were conducted for optimum formulation. Results, discussion and conclusion: F18 containing castor oil, 0.9 mL; PEG 600, 1.36 mL and Tween 80, 2.74 mL was found to be optimum. The optimised formulation had shown uniform globule size, no interactions of LSP with SNEDDS components and higher pharmacokinetic parameters than that of commercial preparation.

Potentials of Mangifera indica in the treatment of depressive-anxiety disorders: possible mechanisms of action.

BACKGROUND: Mangifera indica (Anacardiaceae) is an important herb in the traditional African and Ayurvedic medicines. The stem barks are used in the treatment of hypertension, insomnia, tumour, depression, rheumatism and as a tonic. This study was carried out to investigate antidepressant- and anxiolytic-like effect of the hydroethanol stem bark extract of M. indica (HeMI) in mice. METHODS: HeMI (12.5-100 mg/kg, p.o.) was administered 1 h before subjecting the animal to the forced swim test (FST), tail suspension test (TST) and elevated plus maze tests (EPM). RESULTS: HeMI (12.5-100 mg/kg, p.o.) treatment produced significant reduction in immobility time [F(6.56)=8.35, p<0.001], [F(6,56)=7.55, p<0.001] in the FST and TST, respectively. Moreover, co-administration of sub-therapeutic doses of imipramine or fluoxetine with HeMI (3.125 mg/kg) elicited significant reduction in time spent immobile in the FST. However, pretreatment of mice with parachlorophenylalanine, metergoline, yohimbine or sulpiride abolished the antidepressant-like effect elicited by HeMI. In the EPM, HeMI produced significant [F(5,42)=8.91, p<0.001] increase in open arms exploration by 75.55 % and this effect was blocked by pretreatment of mice with flumazenil or metergoline. CONCLUSIONS: Findings from this study showed antidepressant-like effect of M. indica through interaction with 5-HT2 receptor, α2-adrenoceptor and dopamine D2-receptors. Also, an anxiolytic-like effect through its affinity for 5-HT2 and benzodiazepine receptors. Hence, M. indica could be a potential phytotherapeutic agent in the treatment of mixed anxiety-depressive illness.

The opioid system contributes to the acquisition of reinforcement for dietary fat but is not required for its maintenance.

The opioid system plays an important role in ingestive behavior, especially with regard to palatable high-fat or sweetened foods. In the present study, we investigated the role of the opioid system in the regulation of ingestive behavior in mice with regard to dietary fat intake, reinforcement, and particularly the processes involved in development of these behavior types. Subcutaneous administration of the non-selective opioid receptor antagonist naltrexone (0.5 or 2.0mg/kg body weight [BW]) reduced the spontaneous intake of fat emulsion (Intralipid). We investigated the effect of naltrexone on reinforcement by using an operant behavioral paradigm under a progressive ratio schedule in which the number of lever presses required to obtain a test sample increased progressively. Mice showed stronger reinforcement by Intralipid as a function of concentration. However, naltrexone (0.5 or 2.0mg/kg BW) did not affect reinforcement at any concentration of Intralipid in mice that had repeatedly ingested Intralipid before testing was carried out. Intralipid ingestion also induced conditioned place preference (CPP), which is another evaluation index of reinforcement. High-dose naltrexone (2.0mg/kg BW) administration during CPP conditioning suppressed the reinforcement induced by Intralipid ingestion, although the drug administration (0.5 or 2.0mg/kg BW) during CPP testing did not affect reinforced behavior. These results suggest that the amount of fat ingestion and reinforcement for fat ingestion are separately regulated by the opioid system. Furthermore, our results indicate that the opioid system plays an important role in acquiring reinforcement for fat but is not required for maintenance of learned reinforcement.

Antidepressant and anxiolytic effects of the methanol root extract of Capparis thonningii: involvement of monoaminergic, cholinergic and GABAergic systems.

BACKGROUND: Capparis thonningii Schum. (Capparaceae) is used in traditional African Medicine for the treatment of mood disorders. OBJECTIVE: The study investigates antidepressant and anxiolytic activities of methanol root extract of C. thonningii (CT). METHODS: CT (25-100 mg/kg, p. o.) was administered 1 h before behavioral studies were carried out in mice. Antidepressant effect was investigated using the forced swimming test (FST) and tail suspension test (TST). The anxiolytic effect was evaluated using the elevated-plus maze test (EPM), hole-board test (HBT), and light-dark test. RESULTS: CT (25 and 50 mg/kg) increased swimming activity (P<0.05) by 92.73% and attenuated immobility time by 35.72%, similar to anti-immobility effect of imipramine (33.87%) in FST. In addition, CT (50 mg/kg) significantly (P<0.01) reduced immobility time by 30.24% in TST. -However, the antidepressant-like effect elicited by CT was reversed by metergoline, cyproheptadine, and sulpiride (40.81, 45.93, and 48.52%, respectively) pretreatment but prazosin, and yohimbine failed to reverse this antidepressant-like effect. Similar to diazepam, CT (25 mg/kg) increased duration of open arms exploration (P<0.05) by 43.73% in EPM, number of head-dips (HBT) (90.32%), and time spent in the light compartment by 45.77% in light/dark test indicating anxiolytic-like effect. The anxiolytic-like effect of CT was reversed by flumazenil pretreatment. CONCLUSION: The findings from this study suggest antidepressant-like effect of C. thonningii involving interaction with serotonergic (5-HT2), dopaminergic (D2), noradrenergic (α1 and α2), and muscarinic cholinergic systems; and anxiolytic effect through an interaction with GABAA benzodiazepine receptor.

Effects of dopamine D2/D3 blockade on human sensory and sensorimotor gating in initially antipsychotic-naive, first-episode schizophrenia patients.

It has been suggested that psychophysiological measures of sensory and sensorimotor gating, P50 gating and prepulse inhibition of the startle reflex (PPI), underlie core features of schizophrenia and are linked to dopaminergic pathways in the striatum and prefrontal cortex. In the present study, the effects of a potent D2/D3 receptor antagonist, amisulpride, were investigated on PPI and P50 gating in a large sample of antipsychotic-naive, first-episode patients with schizophrenia. A total of 52 initially antipsychotic-naive, first-episode schizophrenia patients were assessed for their P50 gating, PPI, and habituation/sensitization abilities at baseline and after 2 and 6 weeks of treatment with flexible doses of amisulpride. In addition, 47 matched healthy controls were assessed at baseline and after 6 weeks. At baseline, the patients showed significantly reduced PPI, yet normal levels of P50 gating, habituation, and sensitization. Treatment with amisulpride showed no effects on these measures, either at 2 or 6 weeks of follow-up. This is the first study investigating the effects of monotherapy with a relatively selective dopamine D2/D3 receptor antagonist (amisulpride) on sensory and sensorimotor gating deficits in a longitudinal study of a large group of initially antipsychotic-naive, first-episode patients with schizophrenia. Our finding that amisulpride effectively reduced symptom severity in our patients without reducing their PPI deficits indicates that increased activity of dopamine D2 receptors may be involved in symptomatology of patients with schizophrenia, but not in their sensorimotor gating deficits.

Influence of aripiprazole, risperidone, and amisulpride on sensory and sensorimotor gating in healthy 'low and high gating' humans and relation to psychometry.

Despite advances in the treatment of schizophrenia spectrum disorders with atypical antipsychotics (AAPs), there is still need for compounds with improved efficacy/side-effect ratios. Evidence from challenge studies suggests that the assessment of gating functions in humans and rodents with naturally low-gating levels might be a useful model to screen for novel compounds with antipsychotic properties. To further evaluate and extend this translational approach, three AAPs were examined. Compounds without antipsychotic properties served as negative control treatments. In a placebo-controlled, within-subject design, healthy males received either single doses of aripiprazole and risperidone (n=28), amisulpride and lorazepam (n=30), or modafinil and valproate (n=30), and placebo. Prepulse inhibiton (PPI) and P50 suppression were assessed. Clinically associated symptoms were evaluated using the SCL-90-R. Aripiprazole, risperidone, and amisulpride increased P50 suppression in low P50 gaters. Lorazepam, modafinil, and valproate did not influence P50 suppression in low gaters. Furthermore, low P50 gaters scored significantly higher on the SCL-90-R than high P50 gaters. Aripiprazole increased PPI in low PPI gaters, whereas modafinil and lorazepam attenuated PPI in both groups. Risperidone, amisulpride, and valproate did not influence PPI. P50 suppression in low gaters appears to be an antipsychotic-sensitive neurophysiologic marker. This conclusion is supported by the association of low P50 suppression and higher clinically associated scores. Furthermore, PPI might be sensitive for atypical mechanisms of antipsychotic medication. The translational model investigating differential effects of AAPs on gating in healthy subjects with naturally low gating can be beneficial for phase II/III development plans by providing additional information for critical decision making.

Effects of SCH-23390 and sulpiride on active avoidance in ovariectomized rats treated with a low dose of 17ß-estradiol.

We studied the effects of dopamine D1/D2 receptor antagonists on the dynamics of acquisition and extinction of active avoidance responses and open field behavior in ovariectomized female rats. Dopamine D1 receptor antagonist SCH-23390 (0.1 mg/kg intraperitoneally) and dopamine D2 receptor antagonist sulpiride (10.0 mg/kg intraperitoneally) were administered chronically (14 days) either alone or in combination with a low dose of 17ß-estradiol (0.5 µg per rat subcutaneously) to females after ovariectomy. It was found that SCH-23390 in combination with a low dose of 17ß-estradiol completely restored impaired conditioning and retention of a conditioned avoidance response in ovariectomized animals. Simultaneous correction of behavioral patterns in the open field test was also observed in ovariectomized females receiving SCH-23390. Sulpiride injected alone or in combination with low dose of 17ß-estradiol did not correct conditioning and reproduction of active avoidance response in females with estrogen deficiency and did not significantly affect animal behavior. The results indicate positive effect of dopamine D1 receptor blockade on active learning under conditions of estrogen deficiency.

Involvement of dopaminergic receptors of the rat nucleus accumbens in decreasing the conditioned place preference induced by lateral hypothalamus stimulation.

Our previous study showed that chemical stimulation of the lateral hypothalamus (LH) by carbachol can produce conditioned place preference (CPP) in rats. Also, it has been indicated that orexin activates the mesolimbic dopamine projecting neurons to the nucleus accumbens (NAc) and promotes the development of reward in rodents. Therefore, in this study, we tried to determine the role of intra-accumbal D1 and D2 dopamine receptors in the development (acquisition) of reward-related behaviors induced by chemical stimulation of the LH. Eighty-eight adult male Wistar rats were unilaterally implanted by two separate cannulae into the LH and NAc. For chemical stimulation of LH, carbachol (250nmol/0.5µl saline) was microinjected once daily during 3-days conditioning phase (acquisition period) of CPP paradigm. In the next experiments, different doses of D1 receptor antagonist, SCH23390 (0.25, 1 and 4µg/0.5µl saline) or sulpiride (0.25, 1 and 4µg/0.5µl DMSO) as a D2 receptor antagonist were unilaterally microinjected into the NAc, 5min prior to LH stimulation. One-way ANOVA showed that intra-accumbal administration of SCH23390 or sulpiride can decrease the development of LH stimulation-induced CPP in the rats. However, this decrease is more effective after blockade of the D2 dopamine receptor in the NAc. It seems that the dopaminergic system in this area is involved in place preference induced by LH stimulation.

Proline-induced changes in acetylcholinesterase activity and gene expression in zebrafish brain: reversal by antipsychotic drugs.

Hyperprolinemia is an inherited disorder of proline metabolism and hyperprolinemic patients can present neurological manifestations, such as seizures, cognitive dysfunctions, and schizoaffective disorders. However, the mechanisms related to these symptoms are still unclear. In the present study, we evaluated the in vivo and in vitro effects of proline on acetylcholinesterase (AChE) activity and gene expression in the zebrafish brain. For the in vivo studies, animals were exposed at two proline concentrations (1.5 and 3.0mM) during 1h or 7 days (short- or long-term treatments, respectively). For the in vitro assays, different proline concentrations (ranging from 3.0 to 1000 µM) were tested. Long-term proline exposures significantly increased AChE activity for both treated groups when compared to the control (34% and 39%). Moreover, the proline-induced increase on AChE activity was completely reverted by acute administration of antipsychotic drugs (haloperidol and sulpiride), as well as the changes induced in ache expression. When assessed in vitro, proline did not promote significant changes in AChE activity. Altogether, these data indicate that the enzyme responsible for the control of acetylcholine levels might be altered after proline exposure in the adult zebrafish. These findings contribute for better understanding of the pathophysiology of hyperprolinemia and might reinforce the use of the zebrafish as a complementary vertebrate model for studying inborn errors of amino acid metabolism.

Continuous stress promotes expression of VGF in melanotroph via suppression of dopamine.

Prolonged exposure to stress elicits profound effects on homeostasis that may lead to cryptogenic disorders such as chronic fatigue syndrome. To investigate the pathophysiology associated with the syndrome, we used a rat continuous stress (CS) model where the pituitary represents one of the most affected organs. Here we found that mRNA for VGF (non-acronymic), a member of the granin family, was induced specifically in the intermediate lobe (IL). This was matched by a concomitant increase at the peptide/protein level assessed by C-terminal antibody. Furthermore, the up-regulation of VGF was confirmed by immunohistochemistry in a subset of melanotrophs. VGF expression was altered in the IL of rats receivingthe dopamine D2 receptor agonist bromocriptine or the antagonist sulpiride. In vitro, dopamine dose-dependently decreased the mRNA levels in cultured melanotrophs. These findings suggest that VGF expression under CS is negatively regulated by dopaminergic neurons projecting from the hypothalamus.

[Significance of CRF and dopamine receptors in amygdala for reinforcing effects of opiates and opioids on self-stimulation of lateral hypothalamus in rats].

Bipolar electrodes were implanted in the lateral hypothalamus in a group of 44 Wistar male rats in order to study self-stimulation reaction in the Skinner box. Simultaneously, microcanules were implanted into the central nucleus of the amygdala to inject the drugs (1 microl per injection). The blockade of corticoliberin (CRF) receptors (astressin, 1 microg) or Na+influx currents (xycaine or lidocain 1 microg) by the intrastructural administration of drugs into the amygdala decreased self-stimulation reaction of the lateral hypothalamus in rats by 29-55%. The inhibition of D1 and D2 dopamine receptors in the amygdala with SCH23390 (1 microg) or sulpiride (1 microg) respectively, also reduced self-stimulation but to a lower degree. On the background of blockade of CRF (astressin) and dopamine (sulpiride) receptors as well as sodium influx ionic currents (lidocain) in the amygdala neurons, psychomotor stimulant amphetamine (1 mg/kg) and barbiturate sodium ethaminal (5 mg/kg) retained their psychoactivating effect on self-stimulation (+30-37%), while fentanyl (0.1 mg/kg) and leu-enkephaline (0.1 mg/kg) did not produce this effect. Fentanyl moderately activated self-stimulation only after the blockade of D1 dopamine receptors with SCH23390. After the blockade of CRF receptors, leu-enkephaline strengthened its depressant effect on self-stimulation reaction (-89%). Therefore, if the modulating action of amygdala on the hypothalamus is eliminated, the enhancing effects of opiates (fentanyl) and opioids (leu-encephaline) are blocked, but the effects of psychomotor stimulant amphetamine and barbiturate sodium ethaminal are retained.