Iron Deficiency Alters Discrete Proteins in Rat Caudate Nucleus and Nucleus Accumbens

Young rats (21 days old) made nutritionally iron deficient, by feeding them a semisynthetic diet containing skimmed milk for 5 weeks, had significantly lowered hemoglobin levels (5.2 +/- 4 g/100 ml). The nonheme iron content in caudate nucleus was decreased by 47%. The behavioral response of iron-deficient rats to apomorphine (2 mg/kg) and the density of 3,4-dihydroxyphenylethylamine (dopamine) D2 receptors, as measured by [3H]spiperone binding in caudate nucleus, were significantly reduced by 70 and 53%, respectively. The possibility that nutritional iron deficiency may affect protein content in brain was investigated by measuring the apparent concentration of proteins in caudate nucleus and nucleus accumbens from iron-deficient and control animals using two-dimensional gel electrophoresis. The data indicate that iron deficiency can affect content in these two brain regions. Significant changes in the content of 10 proteins were noted in the caudate nucleus and nucleus accumbens in iron-deficient rats. The albumin level was significantly increased in both regions studied, whereas the neuron-specific enolase level was increased in the nucleus accumbens and the glial fibrillary acidic protein level was reduced in the caudate nucleus. The significance of these protein content changes, as well as a reduction in content of a 94-kilodalton protein (a molecular size similar to that of the D2 dopamine receptor), remains to be established.     

Modulation by GTP of Basal and Agonist-Stimulated Striatal Adenylate Cyclase Activity Following Chronic Blockade of D1 and D2 Dopamine Receptors: Involvement of G Proteins in the Development of Receptor Supersensitivity

Rats receiving injections of specific antagonists of dopamine receptors (SCH 23390 for D1, haloperidol for D2, and haloperidol+SCH 23390) once daily for 21 days develop a selective supersensitivity of the blocked receptors. To study the molecular correlates of these adaptive changes, we evaluated the involvement of GTP-binding proteins in the development of supersensitivity of dopamine receptors. By means of adenylate cyclase studies, we tested whether any of the treatments modified the functional response to GTP in striata dissected from control and treated rats. Our data show that the chronic blockade of D1 and/or D2 receptors potentiates both basal and dopamine receptor-stimulated adenylate cyclase activity in response to GTP. D1 receptor up-regulation correlates with an increased adenylate cyclase response to GTP, whereas D2 receptor up-regulation is accompanied by an enhanced GTP-induced inhibition of enzyme activity, in both basal and receptor-activated conditions. This potentiation does not seem to match the changes in mRNA content of Gs and Gi alpha subunits. Unexpectedly, however, a significant increase in Gi alpha subunit mRNA was found after the chronic blockade of D1 receptors; this result could be explained by cross-regulation between GTP-binding protein-mediated pathways. This cross-regulation could serve as a protective mechanism whereby cells exposing up-regulated receptors protect themselves from a condition of hyperactivity of the adenylate cyclase enzyme.     

Supersensitivity of sigma receptors after repeated administration of cocaine.

We investigated the role of sigma receptors in the expression of behavioral sensitization induced by cocaine. Rats received intraperitoneal injections of either 20 mg/kg cocaine or saline once daily for 14 consecutive days. Cocaine-treated rats became sensitized. After a 5-day abstinence period, a challenge dose of (+)-3-[3-hydroxyphenyl]-N-(1-propyl)piperidine ((+)-3-PPP), a sigma receptor agonist, was administered. (+)-3-PPP at doses of 12 and 24 mg/kg induced significantly more frequent rearing and more potent stereotypy consisting of repetitive head movement and sniffing in cocaine-sensitized rats than in saline-pretreated rats. These enhanced responses to (+)-3-PPP lasted for at least a month. The enhanced responses to (+)-3-PPP were attenuated by 30 mg/kg BMY 14802, a putative sigma antagonist, and also attenuated by 100 mg/kg (+/-)-sulpiride, a D2 dopamine antagonist. These findings show that repeated administration of cocaine produces lasting supersensitivity of simga receptors, which may induce subsequent activation of dopaminergic transmission.     

No change in dopamine D1 receptor in vivo binding in rats after sub-chronic haloperidol treatment

A frequent side effect in the long-term treatment of schizophrenia with the dopamine D2 antagonist haloperidol (HAL) is the appearance of tardive dyskinesia or, in animals, of repetitive involuntary vacuous chewing movements (VCMs). In rats, chronic HAL-induced or D1 receptor-stimulated VCMs are suppressed by D1 antagonists, suggesting that this behavioral supersensitivity is mediated by D1 receptors. The goal of this study was to investigate in vivo the possible relationship between D1 receptor binding and D1-mediated behavioral supersensitivity, after subchronic HAL treatments. D1 agonist R-SKF 82957 and antagonist SCH 23390, both labeled with carbon-11, were used to assess in vivo D1 receptor binding. Rats were treated with HAL (1.5 mg/kg, i.p.) or vehicle for 21 days, followed by a 4 day washout period. No significant difference was found in the regional brain binding of either radioligand. D1 receptor-mediated behaviors including VCMs, grooming, and rearing were measured in control or HAL-treated rats. VCMs were significantly increased in HAL-treated rats, suggesting D1 receptor stimulation and possibly receptor supersensitivity. This study failed to link the purported D1 receptor-mediated behaviors with in vivo receptor binding measures of R-[11C]SKF 82957 or [11C]SCH 23390 in rat brain regions.     

Age related alterations of motor behavior and release of dopaminergic supersensitivity in rats

Rats aged greater than or equal to 18 months show, aside from clearly diminished motor parameters (exploratory behavior, resting activity, nocturnal activity profile, rotation behavior), after intracerebral dopamine injection a considerably lower apomorphine hypermotility than young animals. The characteristic alteration of activity occurring in young rats during and following chronic administration of haloperidol (1 mg/kg . day, s.c. for 21 days) as an expression of developing dopaminergic supersensitivity does not appear in older animals. Repeated application of amphetamine (2 X 2 mg/kg daily) caused a significant increase in hypermotility. The results are interpreted as the consequence of a age-related reduction of the activity of central-dopaminergic transmission systems and are discussed with regard to possible differences in the realization of agonist- or antagonist-induced supersensitivity.     

The effect of chronic levodopa on haloperidol induced behavioral supersensitivity in the guinea pig

The effect of chronic levodopa-carbidopa administration (200 mg/kg for 21 days) on guinea pigs rendered behaviorally supersensitive by the prior administration of haloperidol (.5 mg/kg for 21 days) was examined. Animals who showed an increased behavioral response to apomorphine after chronic haloperidol administration were treated with levodopa-carbidopa and then apomorphine - induced stereotypy was reexamined. Although the chronic levodopa control groups and the chronic haloperidol control remained supersensitive to the behavioral effect of apomorphine, the haloperidol-levodopa group's behavioral response to apomorphine returned to normal. Both chronic dopaminergic antagonist and agonist administration have been demonstrated to induce heightened apomorphine-induced stereotypy and this has been interpreted as a reflection of altered striatal dopamine receptor site sensitivity. The finding that the serial administration of a chronic dopaminergic antagonist followed by a chronic dopaminergic agonist results in a return to normal of a striatal dopamine receptor-dependent behavior suggests that these chronic treatments affect dopamine receptor sites by different mechanisms of action. Since neuroleptic induced dopaminergic supersensitivity in animals is an accepted model of tardive dyskinesia, levodopa may also reverse dopaminergic supersensitivity in patients and might be a potential therapeutic agent in tardive dyskinesia.     

Down-regulation of haloperidol-induced striatal dopamine receptor supersensitivity by active analogues of L-prolyl-L-leucyl-glycinamide (PLG)

Tardive dyskinesia, a clinical syndrome, is one of the major side effects of protracted treatment with neuroleptics in schizophrenic patients. Functional supersensitivity of striatal dopamine receptors is believed to contribute to the pathogenesis of schizophrenia and tardive dyskinesia. In a rodent model of neuroleptic-induced dopamine receptor supersensitivity, we investigated the efficacy of structurally modified analogues of PLG to down-regulate the striatal dopamine receptor supersensitivity as determined by alterations in [³H]spiroperidol binding to striatal membranes in vitro. The PLG analogue, L-prolyl-L-leucyl-(+)-thiazolidine-2-carboxamide-HCl, when given at the dose of 10 mg/kg IP for 5 days prior to haloperidol (3 mg/kg IP 21 days) significantly prevented the up-regulation of striatal dopamine receptor supersensitivity, thus demonstrating a prophylactic effect. Two other analogues, L-prolyl-L-leucyl-5-aminomethyltetrazole and L-prolyl-L-leucyl-glycine-dimethylamide at a dose of 10 mg/kg IP when given concurrently with haloperidol for 21 days, suppressed the development of dopamine receptor supersensitivity. None of the analogues tested in the post-haloperidol session reversed the haloperidol-induced increase in the density of striatal dopamine receptors. Active PLG analogues hold promise as potential therapeutic agents for the amelioration of tardive dyskinesia.     

Concurrent treatment with benztropine and haloperidol attenuates development of behavioral hypersensitivity but not dopamine receptor proliferation

Groups of male rats (n = 16 each) were treated with normal saline, haloperidol (0.75 mg/kg), benztropine (1.8 mg/kg) or haloperidol and benztropine once a day for 24 days. Following a 96 hour drug free interval, subsets of these animals were assessed for apomorphine-induced (0.75 mg/kg) stereotypic behavior, sacrificed and analyzed for striatal dopamine biochemistry or sacrificed and analyzed for spiroperidol binding sites. Benztropine cotreatment attenuated the development of behavioral hypersensitivity to haloperidol but did not alter either the dopamine receptor proliferation or the striatal dopamine biochemical changes induced by haloperidol. These results suggest that behavioral hypersensitivity is not an automatic manifestation of dopamine receptor proliferation but must depend, in part, on other factors.     

Effect of Iron Chelators on Dopamine D2 Receptors

Nutritional iron deficiency induced in rats causes a selective reduction of [3H]spiperone binding in caudate nucleus. This effect can be reversed by iron supplementation in vivo. The possibility that iron may be involved in the dopamine D2 receptor was investigated by examining the effect of various iron and noniron chelators on the binding of [3H]spiperone in rat caudate nucleus. Iron chelators 1,10-phenanthroline, 2,4,6-tripyridyl-s-triazine, alpha, alpha'-dipyridyl, and desferrioxamine mesylate inhibited the binding of [3H]spiperone. The inhibition by 1,10-phenanthroline was noncompetitive and reversible. In the presence of FeCl2 or FeCl3, the inhibitory effect of 1,10-phenanthroline was potentiated. Iron salts or chelators were without effect on the binding of [3H]dihydroalprenolol to beta-adrenoreceptors in caudate nucleus; thus the action of iron chelators on the dopamine D2 receptor tends to be selective. Incubation of caudate nucleus membrane prepared from iron-deficient rats with FeCl2 or FeCl3 did not reverse the diminished binding of [3H]spiperone. The present study indicates that if iron is involved in the physiological regulation of dopamine D2 agonist-antagonist binding sites, it is more complex than hitherto considered.     

Effect of chronic treatment with haloperidol on vasopressin release and behavioral changes by osmotic stimulation of the supraoptic nucleus.

Chronic treatment with dopamine D2 blockers in schizophrenic patients has been proposed as one of the causes of polydipsia and water intoxication, but this conclusion is still controversial. To investigate the relationship between dopamine D2 blockers and these syndromes, we designed a behavioral and neurochemical study using hyperosmotic stimulation in the supraoptic nucleus (SON) by microdialysis after chronic treatment with haloperidol in rats. Animals were injected with haloperidol decanoate (20 mg/kg, i.m.) or sesame oil at 2-week intervals for 8 successive weeks. During the 7th week, water-intake was increased 30-60 min after the hyperosmotic stimulation in both groups, but more so in haloperidol-treated animals compared to that in the control group. Moreover, arginine vasopressin (AVP) was released by the hyperosmotic stimulation in SON, but was not significantly different between groups. In addition, striatal dopamine levels 3-4 days after the microdialysis study showed a significant decrease in the haloperidol-treated animals. These results suggest that chronic treatment with haloperidol enhances water-intake produced by hyperosmotic stimulation in the SON but does not increase AVP levels in dialysates following hyperosmotic stimulation. Thus, these symptoms may be mediated by dopaminergic systems in brain.     

Iron-responsive olfactory uptake of manganese improves motor function deficits associated with iron deficiency

Iron-responsive manganese uptake is increased in iron-deficient rats, suggesting that toxicity related to manganese exposure could be modified by iron status. To explore possible interactions, the distribution of intranasally-instilled manganese in control and iron-deficient rat brain was characterized by quantitative image analysis using T1-weighted magnetic resonance imaging (MRI). Manganese accumulation in the brain of iron-deficient rats was doubled after intranasal administration of MnCl(2) for 1- or 3-week. Enhanced manganese level was observed in specific brain regions of iron-deficient rats, including the striatum, hippocampus, and prefrontal cortex. Iron-deficient rats spent reduced time on a standard accelerating rotarod bar before falling and with lower peak speed compared to controls; unexpectedly, these measures of motor function significantly improved in iron-deficient rats intranasally-instilled with MnCl(2). Although tissue dopamine concentrations were similar in the striatum, dopamine transporter (DAT) and dopamine receptor D(1) (D1R) levels were reduced and dopamine receptor D(2) (D2R) levels were increased in manganese-instilled rats, suggesting that manganese-induced changes in post-synaptic dopaminergic signaling contribute to the compensatory effect. Enhanced olfactory manganese uptake during iron deficiency appears to be a programmed "rescue response" with beneficial influence on motor impairment due to low iron status.     

Rolipram,a selective c-AMP phosphodiesterase inhibitor suppresses oro-facial dyskinetic movements in rats

Since striatal dopamine D2 receptor supersensitivity in the etiology of tardive dyskinesia has been suggested and dopamine D2 receptors are known to inhibit adenylate cyclase activity resulting in a decrease of cyclic adenosine 3′,5′-monophosphate (cAMP) levels, we hypothesized that an increase in cAMP levels ameliorates the condition. In the present study, 21-day haloperidol treatment (1.5 mg/kg I.P.) in rats resulted in an increase in striatal [³H]-spiperone (D2) binding whereas [³H] SCH23390 (D1) binding was unaltered. This haloperidol treatment also induced a significantly increase in the frequency of involuntary chewing movements and tongue protrusions, which are considered as a model of tardive dyskinesia. These dyskinetic movements were suppressed by administration of rolipram (0.5 and 1.0 mg/kg I.P.), an inhibitor of the cAMP phosphodiesterase type IV. The present results suggest that selective cAMP phosphodiesterase type IV inhibitors could be putative therapeutic drugs for tardive dyskinesia.     

Effects of cyclo (Leu-Gly) on neurochemical indices of striatal dopaminergic supersensitivity induced by prolonged haloperidol treatment

The effects of a prolonged treatment with cyclo (Leu-Gly) and/or haloperidol on biochemical parameters indicative of striatal dopamine target cell supersensitivity have been investigated in the rat. When given acutely, cyclo (Leu-Gly) (2 mg/kg sc) did not affect striatal homovanillic acid, dihydroxyphenylacetic acid and acetylcholine levels both under basal conditions or after acute haloperidol (1 mg/kg ip) treatment. When given concomitantly with haloperidol (infused by means of osmotic minipumps at a rate of 2.5 μg/h sc) for 14 days, cyclo (Leu-Gly) (2 mg/kg sc once daily) failed to prevent the fall of striatal dopamine metabolites observed 2 days following withdrawal and the tolerance to the elevation of dopamine metabolites which occurs in response to challenge with the neuroleptic during withdrawal. Prolonged treatment with cyclo (Leu-Gly) also failed to affect the tolerance to the decrease of striatal acetylcholine levels which occurs under chronic haloperidol treatment. These data suggest that the mechanism whereby cyclo (Leu-Gly) inhibits the development of neuroleptic-induced dopaminergic supersensitivity does not involve an action of the peptide on nigro-striatal dopaminergic and striatal cholinergic neurons and is probably exerted distally to both dopaminergic and cholinergic synapses.     

Regulation of D1A and D2 dopamine receptor mRNA during ontogenesis, lesion and chronic antagonist treatment.

The developmental characteristics of D1A and D2 dopamine receptor mRNA levels were determined by Northern blot analyses. Striatal D1A and D2 dopamine receptor mRNAs of male Fischer 344 rats were about 60% of adult (day 120) levels at postnatal day 1 and reached their highest levels at day 30 (126 and 139% adult levels) and then decreased by day 120 (100%). D1 and D2 dopamine receptors showed much greater quantitative changes with densities at day 30 about 6- and 14-fold higher than at day 1, respectively, while mRNA levels showed only a 2-fold increase. The highest level of D2 dopamine receptor mRNA in the midbrain was reached at day 14 (195% of adult levels) while the level at day 1 was 31% higher than that at day 120. Striatal beta-actin mRNA levels decreased gradually as the rats developed with the level at postnatal day 1 almost twice that at day 120 postpartum. Treatment of adult rats with the selective D2 dopamine receptor antagonist, haloperidol (0.5 mg/kg/day, s.c., for 2 h, 7, 14, 21 days or 21 days + 3 days withdrawal) had no effect on striatal D2 dopamine receptor mRNA levels in spite of significant increases in dopamine receptor density at the later time points. However, 21 days following a 6-hydroxydopamine lesion of the nigrostriatal pathway, striatal D2 dopamine receptor mRNA levels were increased by 53%.     

Chronic haloperidol treatment increased calcium-dependent phosphorylation in rat striatum

In previous studies, we observed that when rats were chronically treated wih haloperidol, there was a significant increase of calmodulin activity in their striatal membranes. Calmodulin is known to modulate calcium-dependent protein phosphorylation in neural membranes. In the present study, we found that the total 32P-incorporation in the striatal proteins from chronic haloperidol-treated rats was significantly increased in comparison to saline-treated rats. A majority of the phosphorylation was attributed to the calcium-mediated activity, since it could be blocked by a calcium chelating agent (EGTA). By using EGTA to inhibit phosphorylation, the results indicated that the haloperidol-treated rats had approximately 3.5-fold greater Ca++-dependent protein kinase activity than the saline-treated rats. Exogenous calcium alone was insufficient to stimulate phosphorylation in the haloperidol-treated rats to the same magnitude as in the saline-treated rats. Calmodulin may be required. 32P-incorporation of two striatal proteins at molecular weight 40 and 52 kilodaltons were markedly stimulated by calcium. Cyclic AMP-mediated phosphorylation seemed to take only a small part in the alteration of total phosphorylation. Therefore, the increase of calmodulin activity and calcium-dependent phosphorylation appears to play a major role in the drug-induced dopamine receptor supersensitivity in rat striatum.     

Chronic haloperidol treatment potentiates apomorphine- and ethanol-induced hypothermia in the rat

Supersensitivity developed in the central dopaminergic system of the rat after 21 days of chronic haloperidol injection. This was indicated by a higher level of apomorphine-elicited stereotypic behavior and by higher concentrations of striatal ³H-spiroperidol binding sites in haloperidol-treated rats compared to saline-treated controls. The chronic haloperidol treatment did not affect the baseline body temperature but potentiated both apomorphine- and ethanol-induced falls in core temperature. Such potentiation may also be related to dopamine supersensitivity. However, no significant correlation was found between apomorphine- or ethanol-induced hypothermia and apomorphine-elicited stereotypic behavior or the concentration of striatal ³H-spiroperidol binding sites. Hence, the nigrostriatal dopamine system does not appear to be involved in the development of hypothermic responses to these agents.     

Effect of chronic haloperidol and quinacrine coadministration on striatal HVA levels and stereotypic behaviors in response to apomorphine in the rat

The effects of chronic administration of quinacrine, a phospholipase A2 inhibitor, on striatal homovanillic acid (HVA) levels and behavioral sensitivity to challenge with a dopamine agonist were examined in rats. Moreover, the ability of chronic phospholipase A2 inhibition to modulate the behavioral supersensitivity and striatal HVA reduction induced by chronic haloperidol administration was also examined. Daily intraperitoneal injection of quinacrine resulted in a significant reduction of striatal HVA levels. Coadministration of haloperidol with quinacrine in this paradigm caused a more profound reduction of striatal HVA levels than either drug administered alone. That this effect of combined administration is not simply due to postsynaptic effects of quinacrine on dopamine receptor sensitivity is suggested by the fact that behavioral supersensitivity was not induced by quinacrine alone nor was the behavioral supersensitivity induced by the quinacrinehaloperidol combination greater than that induced by chronic haloperidol administration alone. There were no effects of any treatment condition on striatal levels of serotonin (5-HT) or 5-hydroxyindoleacetic acid (5-HIAA). These data implicate phospholipase A2 activity in the regulation of dopaminergic transmission.     

Hepatic adaptations to iron deficiency and exercise training.

Brooks et al. [Am. J. Physiol. 253 (Endocrinol. Metab. 16): E461-E466, 1987] demonstrated an elevated gluconeogenic rate in resting iron-deficient rats. Because physical exercise also imposes demand on this hepatic function, we hypothesized that exercise training superimposed on iron deficiency would augment the hepatic capacity for amino acid transamination/deamination and pyruvate carboxylation. Sprague-Dawley rats (n = 32) were obtained at weaning (21 days of age) and randomly assigned to iron-sufficient (dietary iron = 60 mg iron/kg diet) or iron-deficient (3 mg iron/kg) dietary groups. Dietary groups were subdivided into sedentary and trained subgroups. Treadmill training was 4 wk in duration, 6 days/wk, 1 h/day, 0% grade. Treadmill speed was initially 26.8 m/min and was decreased to 14.3 m/min over the 4-wk training period. The mild exercise-training regimen did not affect any measured variable in iron-sufficient rats. In contrast, in iron-deficient animals, training increased endurance capacity threefold and reduced blood lactate and the lactate-to-alanine ratio during submaximal exercise by 34 and 27%, respectively. The mitochondrial oxidative capacity of gastrocnemius muscle was increased 46% by training. However, the oxidative capacity of liver was not affected by either iron deficiency or training. Maximal rates of pyruvate carboxylation and glutamine metabolism by isolated liver mitochondria were also evaluated. Iron deficiency and training interacted to increase pyruvate carboxylation by intact mitochondria. Glutamine metabolism was increased roughly threefold by iron deficiency alone, and training amplified this effect to a ninefold increase over iron-sufficient animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selective Alteration in Blood-Brain Barrier and Insulin Transport in Iron-Deficient Rats

Nutritional iron deficiency induced in rats causes a significant reduction in level of brain nonheme iron and is accompanied by selective reduction of dopamine D2 receptor Bmax. Our previous studies have clearly demonstrated that these alterations can be restored to normal by supplementation with ferrous sulfate; however, neither brain nonheme iron level nor dopamine D2 receptor Bmax can be increased beyond control values even after long-term iron therapy. The possibility that iron deficiency can induce the breakdown of the blood-brain barrier (BBB) was examined. A 70 and 100% increase in brain uptake index (BUI) for L-glucose and insulin, respectively, were noted in iron-deficient rats. However, the BUI for valine was decreased by 40%, and those for L-norepinephrine and glycine were unchanged. In addition, it was demonstrated that in normal rats insulin is transported into the brain. The data show that iron deficiency selectively affects the integrity of the BBB for insulin, glucose, and valine transport. Whether the effect of iron deficiency on the BBB is at the level of the capillary endothelial cell tight junction is not yet known. However, this study has shown that an important nutritional disorder (iron-deficiency anemia) has a profound effect on the BBB and brain function.     

Effects of haloperidol on rat behavior and density of dopaminergic D2-like receptors

The present work shows the effects of a typical neuroleptic drug (haloperidol, HAL) on rat behavior (catalepsy and locomotor activity) and dopaminergic D2-like receptor densities in the hippocampus and striatum. Male Wistar rats (2-3 months old) were treated daily for 30 days with HAL (0.2 or 1mg/kg, intraperitoneally (i.p.)). At the end of treatment and 1h or 1, 3, 7 and 15 days after drug withdrawal, animals were subjected to behavioral tests and sacrificed afterwards for binding assays. The results showed that behavioral effects with both doses were significant only 1h and 1 day after withdrawal, and similar to controls at the third day. An up-regulation of D2 receptors was observed in the striatum (28% increase) but not in the hippocampus after 24h HAL (1mg/kg) withdrawal. However, an up-regulation was seen in both areas (1mg/kg) 3 days after drug withdrawal (58 and 42% increases in the hippocampus and striatum, respectively), and continued after 7 days of withdrawal only in the striatum (43 and 49% for the doses of 0.2 and 1mg/kg, respectively), suggesting the influence of dose, age, and time of drug withdrawal on these parameters. The up-regulation disappeared after 15 days of haloperidol withdrawal. Increases (72 and 140%) in constant dissociation values (K(d)) values were also observed 7 days after withdrawal. Results show differences on a time-basis between behavioral alterations and dopaminergic D2 receptors up-regulation.