Undernutrition during suckling changes the sensitivity to haloperidol and chlorpromazine in two behavioural measures in weaning rats

Tactile stimulation ameliorates haloperidol-induced movement disturbances in rats by promoting neuromodulation on dopaminergic and glutamatergic systems in nigrostriatal brain area

The antipsychotic haloperidol (HAL) primarily antagonizes dopaminergic type-2 receptors. It is known that antipsychotic treatment are commonly related with extrapyramidal syndrome (EPS), which involves movement disorders such as parkinsonism, akathisia and tardive dyskinesia. Tactile stimulation (TS) has been helpful in animal models of drug abuse and depression, raising our interest in evaluating its possible benefits on extrapyramidal HAL-induced side-effects in male adult rats. Subsequently to a sub-chronic model of EPS, TS reversed orofacial dyskinesia and movement impairments induced by HAL and promoted beneficial modulations on dopaminergic and glutamatergic systems in nigrostriatal brain area. Given these outcomes, it is important to consider that: i) TS can help to control and/or reduce movement disorders consequent to antipsychotic treatment; ii) TS can help to better clarify the imbalanced of dopaminergic system haloperidol promotes. Based on our current and previous studies about the benefits of TS, we hypothesize that the TS may represent an important therapeutic target to treat neuromotor disorders originating in the nigrostriatal system.

Influence of magnesium supplementation on movement side effects related to typical antipsychotic treatment in rats

Chronic use of typical antipsychotic haloperidolis related to movement disturbances such as parkinsonism, akathisia and tardive dyskinesia which have been related to excitotoxicity in extrapyramidal brain areas, requiring their prevention and treatment. In the current study we evaluated the influence of the magnesium on prevention (for 28days before-), reversion (for 12days after-) and concomitant supplementation on haloperidol-induced movement disorders in rats. Sub-chronic haloperidol was related to orofacial dyskinesia (OD) and catalepsy development, increased generation of reactive species (RS) and levels of protein carbonyl (PC) in cortex, striatum and substantia nigra (SN) in all experimental protocols. When provided preventatively, Mg reduced the increase of OD and catalepsy time 14 and 7days after haloperidol administration, respectively. When supplemented after haloperidol-induced OD establishment, Mg reversed this behavior after 12days, while catalepsy was reversed after 6days of Mg supplementation.When Mg was concomitantly supplemented with haloperidol administration, OD and catalepsy were prevented. Moreover, Mg supplementation was able to prevent the RS generation in both cortex and SN, reducing PC levels in all brain areas evaluated. When supplemented after haloperidol, Mg reversed RS generation in cortex and striatum, decreasing PC levels in SN and striatum.The co-administration of haloperidol and Mg supplementation prevented RS generation in cortex, striatum and SN, and PC levels in the SN.These outcomes indicate that Mg supplementation may be a useful alternative to prevent movement disturbances resulting of classic antipsychotic pharmacotherapy as haloperidol.

Magnesium Supplementation Prevents and Reverses Experimentally Induced Movement Disturbances in Rats: Biochemical and Behavioral Parameters

Reserpine administration results in a predictable animal model of orofacial dyskinesia (OD) that has been largely used to access movement disturbances related to extrapyramidal oxidative damage. Here, OD was acutely induced by reserpine (two doses of 0.7 mg/kg subcutaneous (s.c.)), every other day for 3 days), which was administered after (experiment 1) and before (experiment 2) magnesium (Mg) supplementation (40 mg/kg/mL, peroral (p.o.)). In experiment 1, Mg was administered for 28 days before reserpine treatment, while in experiment 2, it was initiated 24 h after the last reserpine administration and was maintained for 10 consecutive days. Experiment 1 (prevention) showed that Mg supplementation was able to prevent reserpine-induced OD and catalepsy development. Mg was also able to prevent reactive species (RS) generation, thus preventing increase of protein carbonyl (PC) levels in both cortex and substantia nigra, but not in striatum. Experiment 2 (reversion) showed that Mg was able to decrease OD and catalepsy at all times assessed. In addition, Mg was able to decrease RS generation, with lower levels of PC in both cortex and striatum, but not in substantia nigra. These outcomes indicate that Mg is an important metal that should be present in the diet, since its intake is able to prevent and minimize the development of movement disorders closely related to oxidative damage in the extrapyramidal brain areas, such as OD.

Effects of omega-3 essential fatty acids (omega-3 EFAs) on motor disorders and memory dysfunction typical neuroleptic-induced: behavioral and biochemical parameter

The effects of fish oil supplementation on motor disorders, memory dysfunction, and lipid peroxidation (LP) induced by typical neuroleptics were studied. Wistar rats received a suspension prepared with fish oil containing omega-3 fatty acids, water, and Tween 80 (1%) in the place of drinking water (FO group) or vehicle (C group) for 8 weeks. After 4 weeks of treatment, half of the animals of both groups were treated with haloperidol (H and FO + H groups; experiment 1), fluphenazine (F and FO + F groups; experiment 2), or vehicle (C group), administered once a week (12 mg/kg/im) for 4 weeks, maintaining the treatment with FO. Extrapyramidal motor disorders by haloperidol and fluphenazine were observed by an increase in vacuous chewing movements and catalepsy (P < 0.05). These effects were reduced by FO treatment (P < 0.05). Both neuroleptics displayed impairment in memory retention observed by latency time to find the original location of platform in water-maze task, after 4 days of training performed in the last treatment week. This effect was reduced by FO (P < 0.05) to both haloperidol and fluphenazine treatments. Haloperidol increased the LP in plasma and hippocampus, and these effects were decreased by FO treatment (P < 0.05). Fluphenazine increased the LP in plasma and substantia nigra, which were completely decreased by FO treatment (P < 0.05). The FO decreased the motor disorders, memory dysfunction, and oxidative damage typical neuroleptic-induced. Our results indicate that FO exhibits a neuroprotector role useful on diseases related to oxidative damages, and may be considered in the prevention of motor and memory side effects induced by the antipsychotic treatment.

Prenatal ethanol preferentially enhances reactivity of the dopamine D1 but not D2 or D3 receptors in offspring

Reports of prenatal ethanol (ETOH) effects on the dopamine system are inconsistent. In an attempt to clarify this issue, dams were given 35% ethanol-derived calories as the sole nutrient source in a liquid diet from the 10th through the 20th day of gestation (ETOH). Controls were pair-fed (PF) an isocaloric liquid diet or given ad libitum access to laboratory chow (LC). Prenatal exposure to both liquid diets reduced body weight of offspring relative to LC controls, more so for ETOH than for PF exposure. Prenatal ETOH also decreased litter size and viability, relative to both LC and PF control groups. On postnatal days 21-23, male and female offspring were given an injection of saline vehicle or one of eight specific dopamine receptor agonists or antagonists. Immediately after injection subjects were placed in individual observation cages, and over the following 30 min, eight behaviors (square entries, grooming, rearing, circling, sniffing, yawning, head and oral movements) were observed and quantified. No prenatal treatment effects on drug-induced behaviors were observed for dopamine D2 (Apomorphine, DPAT or Quinpirole) or D3 (PD 152255, Nafadotride, Apo or Quin effects on yawning) receptor agonists or antagonists, or for the vehicle control. In contrast, prenatal treatment effects were seen with drugs affecting the dopamine D1 receptor. Both D1 agonists (SKF 38393) and antagonists (SCH 23390 and high doses of spiperone) altered behaviors, especially oral and sniffing behaviors, in a manner which suggested enhanced dopamine D1 drug sensitivity in both ETOH and PF offspring relative to LC controls. These results suggest that at this age, both sexes experience a prenatal undernutrition-linked increase in the behavioral response to dopamine D1 agonists and antagonists, which can be intensified by gestational exposure to alcohol.

Pressor Responsiveness to Intravenous Quinpirole is Blunted in Malnourished, Conscious Rats: Central vs. Peripheral and Spinal Mechanisms

In conscious rats, intravenous treatment with the dopamine D2-like receptor agonist quinpirole, elicited a pressor effect, which is attributed to central dopamine D2 receptor-mediated activation of sympathetic outflow associated with arginine vasopressin release. This prominent central effect is opposed to peripheral sympathoinhibitory and spinal depressor effects. The present study investigated the effects of pre- and postnatal undernutrition on the central pressor responsiveness to quinpirole. Malnourished (MalN) rats were obtained by feeding dams a multideficient diet (providing 8% protein) during pregnancy and nursing. At 90 days of age, MalN rats weighed significantly less than control (CNT) rats born to dams fed standard commercially diet (23% protein) during pregnancy and nursing. Baseline mean arterial pressure and heart rate in MalN rats were comparable to those of CNT. Intravenous treatment with quinpirole (0.3 mg/kg) in MalN conscious rats induced a pressor effect, which was significantly reduced in both magnitude and duration, when compared with CNT rats. In both groups studied, pressor response to quinpirole was fully abolished by the peripheral and central dopamine D2 receptor antagonist, metoclopramide (5 mg/kg, i.v.) whereas was significantly enhanced after pretreatment with either intravenous (0.5 mg/kg) or intrathecal (40 microg per rat at T9-T10 level) domperidone, a dopamine D2 receptor antagonist that does not cross the blood-brain barrier. However, even under peripheral and spinal dopamine D2 receptor blockade, maximum pressor effect of quinpirole remained significantly reduced in MalN when compared with CNT rats. Neither the maximum pressor nor the bradycardiac responses to intravenous phenylephrine or arginine vasopressin differed between CNT and MalN rats. This study shows that undernutrition imposed during fetal life and suckling blunted the pressor response to quinpirole in conscious rats. This blunted response appears mainly related to desensitization of brain dopamine D2 receptors rather than enhanced peripheral and/or spinal dopamine D2 receptor-mediated depressor effect or vascular hyporesponsiveness to alpha1-adrenoceptor and vasopressin receptor stimulation.

Blunted central bromocriptine-induced tachycardia in conscious, malnourished rats

Bromocriptine-induced tachycardia, persisting after adrenalectomy, is mediated by central dopamine D2 receptor stimulation through activation of the sympathetic outflow to the heart. The present study investigated the effects of malnutrition during pregnancy on bromocriptine-induced tachycardia in adult conscious rats. Malnourished rats were obtained by feeding dams a multideficient diet (providing 8% protein) during mating and pregnancy. Birth weight was significantly reduced in malnourished rats when compared to control rats born to dams fed standard commercially diet (23% protein) during mating and pregnancy. Baseline mean aortic pressure and heart rate in malnourished rats were comparable to those of well-nourished rats. Tachycardia (33+/-9 beats/min.), but not the hypotensive response to intravenous bromocriptine (150 microg/kg) was significantly reduced in malnourished rats, compared with control rats (70+/-10 beats/min.). In malnourished rats, pretreatment with intravenous domperidone (500 microg/kg) blocked the bromocriptine-induced hypotension, without affecting the tachycardia. Neither cardiac vagal (40+/-6 beats/min.) nor sympathetic tone (76+/-6 beats/min.) was significantly altered by multideficient diet-induced malnutrition (51+/-6 and 67+/-10 beats/min., respectively). In isolated perfused heart preparations from malnourished rats, positive inotropic response to isoproterenol (10-8 to 10-4 M) was not significantly different compared to that in control rats. In summary, malnutrition during foetal life blunted the bromocriptine-induced tachycardia, an effect that could be related to central dopamine D2 receptor desensitization rather than to impairment of autonomic regulation of the heart or cardiac beta-adrenoceptor desensitization.

Influence of the test situation on pup retrieval behavior of normal and undernourished lactating rats

Undernutrition of dams and pups disrupts the retrieval efficiency of mothers. However, if the mothers are assessed in their home cages, they spend more time with their litters. In the present study the effect of test conditions on pup retrieval behavior of mothers receiving a 25% (well-nourished group) and 8% casein diet (undernourished group) was examined. In agreement with previous studies, undernourished mothers spent more time with their litters than well-nourished dams as lactation proceeded. Pup retrieval behavior varied with test conditions. In the first experiment, the maternal behavior of dams was assessed by the standard procedure (pups were separated from their mother and scattered over the floor of the home cage). The mother was then returned and the number of retrieved pups was recorded. From day 3 to 8, the retrieval efficiency of undernourished dams decreased, while the retrieval efficiency of well-nourished mothers did not vary. In the second experiment, mothers were subjected to a single retrieval test (on day 9 of lactation) using the procedure described for experiment 1. No difference between well-nourished and undernourished mothers was observed. In the third experiment, seven-day-old pups were separated from the mothers and returned individually to a clean home cage. Dietary treatment did not affect the retrieval efficiency. However, undernourished dams reconstructed the nest more slowly than did well-nourished dams. Taken together, these results suggest that pup retrieval behavior of the undernourished mother is not impaired by dietary restriction when the maternal environment is disturbed minimally.

Dopaminergic modulation of ventilation in obese Zucker rats

To investigate the hypothesis that the impaired respiratory drive noted in morbid obesity was attributable to altered dopaminergic mechanisms acting on peripheral and/or central chemoreflex sensitivity, seven obese and seven lean Zucker rats were studied at 11 wk of age. Ventilation (VE) was measured by the barometric technique during hyperoxic (100% O(2)), normoxic (21% O(2)), hypoxic (10% O(2)), and hypercapnic (7% CO(2)) exposures after the administration of vehicle (control), haloperidol [Hal, 1 mg/kg, a central and peripheral dopamine (Da) receptor antagonist], or domperidone (Dom, 0.5 mg/kg, a peripheral Da receptor antagonist). In both lean and obese rats, Hal increased tidal volume and decreased respiratory frequency during hyperoxia or normoxia, resulting in an unchanged VE. In contrast, Dom did not affect tidal volume, frequency, or VE during hyperoxia or normoxia. During hypoxia, however, VE significantly increased from 1,132 +/- 136 to 1,348 +/- 98 ml. kg(-1). min(-1) (P < 0.01) after the administration of Dom in obese rats, whereas no change was observed in lean rats. Hal significantly decreased VE during hypoxia compared with control in lean but not obese rats. In both lean and obese rats, Hal decreased VE in response to hypercapnia, whereas Dom had no effect. Our major findings suggest that peripheral chemosensitivity to hypoxia in obese Zucker rats is reduced as a result of an increased dopaminergic receptor modulation in the carotid body.

Effect of mercuric chloride and lead acetate treatment during the second stage of rapid post-natal brain growth on the behavioral response to chlorpromazine and on delta-ALA-D activity in weaning rats

During the early post-natal period the brain is extremely sensitive to external agents. In the present study, we examined the effects of the treatment with lead acetate (3.5 or 7.0 mg/kg) and mercuric chloride (2.5 or 5.0 mg/kg) during the early post-natal period (day 8-12) on the behavioral response to chlorpromazine (CPZ) of 22-day-old rats. The effects of these metals on the sulfhydryl-containing enzyme delta-aminolevulinate dehydratase (delta-ALA-D) were also investigated. Mercuric chloride (2.5 mg/kg) did not affect brain enzyme activity, but caused a significant stimulation of renal delta-ALA-D of 24-day-old rats (27%), while animals treated with 5 mg/kg HgCl(2) showed a small but significant inhibition of cerebral (10%) and renal delta-ALA-D activity (15%). Lead acetate (3.5 or 7 mg/kg) treatment did not affect renal or cerebral delta-ALA-D. Mercuric chloride treatment (5 mg/kg) changed the pattern of open-field activity and the CPZ-induced catalepsy. However, since the undernutrition that accompanied the metal treatment also caused changes in CPZ-induced catalepsy, the effect of mercury on catalepsy could not be clearly established. Lead acetate treatment (7 mg/kg) changed the pattern of open-field motor activity and abolished the decrease in activity observed in control rats. The cataleptic response of animals to CPZ was also affected by lead acetate treatment (7 mg/kg). The increase in activity is compatible with the hyperactivity described in animals exposed to lead for long periods. Thus, the present study suggests that a short exposure to lead or mercury during suckling (second stage of rapid post-natal brain growth) caused permanent changes in locomotor activity that can be interpreted as hyperactivity. Additionally, the behavioral response to CPZ was affected by metal treatment indicating an alteration in the dopaminergic system.