D-amphetamine Sulfate Research Articles

NMR Study of the Molecular Dynamics of D-Amphetamine Sulfate Salt Powder

The temperature dependence of the proton spin–lattice relaxation times was measured for the D-amphetamine sulfate salt in the temperature range from 80 to 466 K. Two minima of T 1 were observed and explained in terms of reorientation of the CH3 and NH3 groups. The T 1 minimum attributed to the motion of methyl groups was analyzed assuming two dynamically inequivalent types of these groups in the unit cell of the studied salt. The activation parameters for the C 3 reorientation of the methyl and ammonium groups were determined. A structural phase transition was evidenced at about 335 K in the polycrystalline sample of the D-amphetamine sulfate salt.

Comparison of the Effects of Deramciclane, Ritanserin and Buspirone on Extracellular Dopamine and Its Metabolites in Striatum and Nucleus Accumbens of Freely Moving Rats

In the present study, we assessed the effect of single graded doses of a putative anxiolytic compound, the 5-HT(2A/C )antagonist, deramciclane fumarate (EGIS-3886), on the dopamine efflux and metabolism in nucleus accumbens and striatum and thus evaluated the dose window for deramciclane to cause adverse effects related to the brain dopaminergic system. Dual probe in vivo microdialysis in freely moving rats was used to compare the effects of graded doses of deramciclane fumarate (3, 10 and 30 mg/kg), 5-HT(2A/C )antagonist ritanserin (1 mg/kg) and a partial 5-HT(1A) agonist buspirone hydrochloride (5 mg/kg) on the extracellular levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in nucleus accumbens and striatum assayed by high performance liquid chromatography with electrochemical detection. The indirect dopamine agonist, D-amphetamine sulfate (2 mg/kg), was used as a positive control. Ritanserin, buspirone and deramciclane 3 and 10 mg/kg had no significant effects on the extracellular dopamine levels in either brain area but deramciclane 30 mg/kg significantly increased accumbal dopamine as well as DOPAC and HVA in both brain areas. As expected, the positive control D-amphetamine significantly increased both striatal and accumbal dopamine levels. The effects of buspirone or the highest deramciclane dose and D-amphetamine on DOPAC and HVA levels were opposite; buspirone and deramciclane increased while D-amphetamine decreased the metabolite levels in both brain areas. The results indicate that a single high dose of deramciclane has the neuroleptic- or buspirone-like effect, particularly in mesolimbic regions. There is at least a 5-fold margin between the anxiolytic and neuroleptic doses of deramciclane in the rat.

Brain vasopressin involvement in behavioral sensitization to amphetamines and drinking hypertonic salt solutions.

Sodium restriction cross-sensitizes rats to the psychomotor effects of amphetamines and activation of brain vasopressin pathways induce a psychomotor sensitization and facilitate salt intake in sodium-deficient rats. In Experiment 1, we tested the hypothesis that male rats previously sensitized to central VP injections would subsequently show enhanced psychomotor responses to amphetamine. Rats were administered either saline, intraventricular injections of VP (50 ng) or amphetamine (1 or 3 mg/kg, d-amphetamine sulfate, i.p.) on two consecutive days. All rats were administered amphetamine on day 3 and behavior was monitored. Amphetamine on day 3 elicited a significantly greater psychomotor response in rats that had two prior injections of amphetamine or VP, than in rats previously treated with saline or those receiving amphetamine for the first time on Day 3. In Experiment 2, the hypothesis that prior experience with central VP would cross-sensitize the rat to drinking hypertonic sodium (NaCl) solutions was tested. Naïve male rats were administered intraventricular injections of VP (50 ng) or isotonic saline for 3 days and on the fourth day non deprived rats were given access to 0.3 M NaCl and water for 1 h. Control (isotonic saline treated) rats only drank 1 ml of 0.3 M NaCl, but need-free rats previously exposed to central VP injections drank significantly more hypertonic saline (4 ml). These results show that prior experience with central VP cross-sensitizes rats to the psychomotor stimulant effects of amphetamine and the ingestion of concentrated NaCl solutions. Supported by NIH DK50586 and RR15640.

Dopaminergic Actions of d-Amphetamine on Schedule-Induced Polydipsia in Rats

Schedule-induced polydipsia in rats was developed by means of a fixed-time 60-s schedule of food presentation. The acute administration of d-amphetamine sulfate (0.1–3.0 mg/kg) produced a dose-dependent decrease in the rate of licking. d-Amphetamine shifted to the left the temporal distribution of adjunctive drinking within interfood intervals. Dopaminergic antagonists SCH23390 ([R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro- 1H-3-benzazepine hydrochloride], 0.001–0.01 mg/kg), eticlopride (0.001–0.03 mg/kg), and flupenthixol (0.03–0.3 mg/kg) also produced dose-dependent decreases in licks per minute but did not alter the temporal distribution of adjunctive behavior. Selective doses of dopaminergic antagonists further suppressed licking rates when combined with d-amphetamine, 1.0 mg/kg, but an antagonism could be observed on the temporal distribution after the administration of SCH23390 (0.01 mg/kg) or flupenthixol (0.1 mg/kg). The dopaminergic agonists SKF38393 ([R(+)-1-phenyl-7,8-dihydroxy-2,3,4,5-tetrahydro-1H-3-bezazepine hydrochloride]; 1.0–10.0 mg/kg) and quinpirole (0.003–0.03 mg/kg) produced a dose-dependent decrease in the rate of licking, and when combined with d-amphetamine, additive-like suppressive effects were found. These results suggest a dopaminergic selectivity for the effects of d-amphetamine on the temporal distribution of schedule-induced polydipsia.

Development and validation of a liquid chromatography/tandem mass spectrometry assay for the simultaneous determination of d-amphetamine and diphenhydramine in beagle dog plasma and its application to a pharmacokinetic study

A new drug, quick-acting anti-motion capsule (QAAMC) composed of d-amphetamine sulfate, dimenhydrinate and ginger extraction has been studied for anti-motion-sickness use. We have developed a sensitive, specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the quantitative determination of d-amphetamine and diphenhydramine, the main effective components of the QAAMC, using pseudoephedrine as the internal standard. The analytes and internal standard were isolated from 200 μL plasma samples by a simple liquid–liquid extraction (LLE). Reverse-phase HPLC separation was accomplished on a Zorbax SB-C18 column (100 mm × 3.0 mm, 3.5 μm) with a mobile phase composed of methanol–water–formic acid (65:35:0.5, v/v/v) at a flow rate of 0.2 mL/min. The method had a chromatographic total run time of 5 min. A Varian 1200 L electrospray tandem mass spectrometer equipped with an electrospray ionization source was operated in selected reaction monitoring (SRM) mode with the precursor-to-product ion transitions m/ z 136.0 → 91.0 ( d-amphetamine), 256.0 → 167.0 (diphenhydramine) and 166.1 → 148.0 (IS) used for quantitation. The method was sensitive with a lower limit of quantitation (LLOQ) of 0.5 ng/mL for d-amphetamine and 1 ng/mL for diphenhydramine, with good linearity in the range 0.5–200 ng/mL for d-amphetamine and 1–500 ng/mL for diphenhydramine ( r 2 ≥ 0.9990). All the validation data, such as accuracy, precision, and inter-day repeatability, were within the required limits. The method was successfully applied to pharmacokinetic study of the QAAMC in beagle dogs.

Differential effects of the d- and l- isomers of amphetamine on pharmacological MRI BOLD contrast in the rat

The D - and L-amphetamine sulphate isomers are used in the formulation of Adderall XR(R), which is effective in the treatment of attention-deficit hyperactivity disorder (ADHD). The effects of these isomers on brain activity has not been examined using neuroimaging. This study determines the pharmacological magnetic resonance imaging blood-oxygenation-level-dependent (BOLD) response in rat brain regions after administration of each isomer. Rats were individually placed into a 2.35 T Bruker magnet for 60 min to achieve basal recording of variation in signal intensity. Either saline (n = 9), D-amphetamine sulphate (2 mg/kg, i.p.; n = 9) or L: -amphetamine sulphate (4 mg/kg, i.p.; n = 9) were administered, and recording continued for a further 90 min. Data were analysed for BOLD effects using statistical parametric maps. Blood pressure, blood gases and respiratory rate were monitored during scanning. The isomers show overlapping effects on the BOLD responses in areas including nucleus accumbens, medial entorhinal cortex, colliculi, field CA1 of hippocampus and thalamic nuclei. The L-isomer produced greater global changes in the positive BOLD response than the D-isomer, including the somatosensory and motor cortices and frontal brain regions such as the orbitofrontal cortices, prelimbic and infralimbic cortex which were not observed with the D-isomer. The amphetamine isomers produce different BOLD responses in brain areas related to cognition, pleasure, pain processing and motor control probably because of variations on brain amine systems such as dopamine and noradrenaline. The isomers may, therefore, have distinct actions on brain regions affected in ADHD patients.

A triazolam/amphetamine dose–effect interaction study: dissociation of effects on memory versus arousal

In addition to producing robust memory impairment, benzodiazepines also induce marked sedation. Thus, it is possible that the observed amnestic effects are secondary to more global sedative effects and do not reflect a specific primary benzodiazepine effect on memory mechanisms. The objective was to use the nonspecific stimulant d-amphetamine to dissociate the sedative and memory-impairing effects of the benzodiazepine triazolam. Single oral doses of placebo, triazolam alone (0.25, 0.50 mg/70 kg), d-amphetamine sulfate alone (20, 30 mg/70 kg), and triazolam (0.25, 0.50 mg/70 kg) and d-amphetamine sulfate (20, 30 mg/70 kg) conjointly (at all dose combinations) were administered to 18 healthy adult participants across nine sessions in a double-blind, staggered-dosing, crossover design. In addition to standard data analyses, analyses were also conducted on z-score standardized data, enabling effects to be directly compared across measures. Relative to the sedative measures, the memory measures generally exhibited a pattern of less reversal of triazolam's effects by d-amphetamine. The memory measures ranged in degree of reversal such that the most reversal was observed for reaction time on the n-back working memory task, and the least reversal was observed for accuracy on the Sternberg working memory task, with most measures showing an overall pattern of partial reversal. Benzodiazepines have specific effects on memory that are not merely a by-product of the drugs' sedative effects, and the degree to which sedative effects contribute to the amnestic effects varies as a function of the particular memory process being assessed.

Clozapine and prazosin slow the rhythm of head movements during focused stereotypy induced by d-amphetamine in rats

Clozapine is an efficacious, symptom-ameliorating, atypical antipsychotic drug with few extrapyramidal side effects. Clozapine has been reported either not to affect or to increase d-amphetamine-induced stereotypy, a behavior that is blocked by typical antipsychotic drugs. This work used a high-resolution measurement system to reassess clozapine's effects on d-amphetamine-induced focused stereotypy (FS) in rats. A force-plate actometer permitted the quantitation of the rhythm and vigor of movements during FS. Eight rats received a sensitizing series of doses of 5.0 mg/kg d-amphetamine sulfate, and this dosing regimen induced head movements with a rhythm near 10 Hz. Thirty minutes after d-amphetamine treatment, rats received acute clozapine (2.5-10.0 mg/kg), followed by eight, daily clozapine injections (5.0 mg/kg) given with d-amphetamine on days 2, 5, and 8. Effects of acute doses of the alpha1-noradrenergic antagonist prazosin (0.5-2.0 mg/kg) on the d-amphetamine response were also examined. Clozapine dose-dependently slowed the near 10-Hz rhythm and reduced the vigor of the d-amphetamine-induced FS. Clozapine significantly lengthened the duration of the FS phase, but the rhythm remained slowed. No evidence for tolerance to clozapine's rhythm-slowing effects was seen in the subchronic phase. Prazosin dose-dependently reduced the near 10-Hz rhythm induced by d-amphetamine, but prazosin did not lengthen the FS phase. The results show that clozapine diminished the rhythm and vigor of d-amphetamine-induced stereotyped head movements but, at the same time, lengthened the duration of the expression of the stereotypy. alpha1 antagonism is a likely contributor to the rhythm-modulating effects of clozapine.

Effects of bilateral vibrissotomy on the expression of focused stereotypy (FS) induced by amphetamine in Sprague Dawley (SD) or Fischer 344 (F344) rats

Above doses of about 2.5 mg/kg in SD rats, amphetamine produces FS, a syndrome characterized by a complete lack of locomotion accompanied by rapid, rhythmic head movements. During these movements, the rat’s vibrissae are stimulated by accelerations of the head and by contact with the floor and walls of the cage. Given that previous reports have linked removal of vibrissae with changes in brain dopamine systems and given amphetamine’s dopamine releasing effects in vivo, we hypothesized that bilateral removal of the vibrissae would alter the FS response to amphetamine. Of additional interest was the question of rat strain differences in response to amphetamine. Accordingly, in a between-groups dosing design male SD and male F344 rats were treated with 0, 1.25, 2.5 and 5.0 mg/kg d-amphetamine sulfate every 4th day for a total of 7 injections, and on the 7th day, amphetamine treatment was accompanied by bilateral vibrissotomy. Behavior was recorded continuously in 4-hr sessions with a force-plate actometer, a new type of technology that permits quantitation of FS without human observers. Vibrissotomy did not alter the basic style of FS for either rat strain where style was assessed by the power spectra of the vertical force component of the head movements. Area-under-the-curve analyses of FS scores showed vibrissotomy increased the intensity of the head movements in the F344 rats but not in the SD rats. Indexes of spatial confinement were not significantly affected. These data suggest that the rhythmic, rapid head movements of FS are probably not sustained by, nor appreciably modulated by sensory feedback from the vibrissae. Supported by MH43429 and HD002528.

Impaired response to amphetamine and neuronal degeneration in the nucleus accumbens of autoimmune MRL-lpr mice

Spontaneous development of lupus-like disease in MRL-lpr mice is accompanied by a constellation of behavioral deficits, including blunted responsiveness to sucrose. Although autoimmunity-induced damage of limbic areas is proposed to underlie this deficit, the systemic nature of the disease precludes inference of a causal relationship between CNS damage and functional loss. Based on the stimulatory effects of d-amphetamine sulfate (AMPH) on sucrose intake, the present study pharmacologically probes the functional status of central dopaminergic circuits involved in control of behavioral reward. The response rates were compared between diseased MRL-lpr mice and congenic MRL +/+ controls tested in the sucrose preference paradigm. Neuronal loss was assessed by Fluoro Jade B (FJB) staining of nucleus accumbens and the CA2/CA3 region. While control mice significantly increased intake of sucrose solutions 60 min after administration of AMPH (i.p., 0.5 mg/kg), the intake in drugged MRL-lpr mice was comparable to those given saline injection. Increased FJB staining was detected in the nucleus accumbens and hippocampus of diseased mice, and AMPH treatment neither altered this nor other measures of organ pathology. The results obtained are consistent with previously observed changes in the mesolimbic dopamine system of MRL-lpr mice and suggest that the lesion in the nucleus accumbens and deficits in dopamine release underlie impaired responsiveness to palatable stimulation during the progress of systemic autoimmune disease. As such, they point to a neurotransmitter-specific regional brain damage which may account for depressive behaviors in neuropsychiatric lupus erythematosus.

Non-linearity in combined effects of ELF magnetic field and amphetamine on motor activity in rats

The effects of short-term (15 min) pre-exposure of rats to extremely low-frequency magnetic field (ELF-MF, 50 Hz, 6 mT) on their motor (locomotor and stereotypic) activity induced by d-amphetamine sulphate (AMPH) at different doses (0.5, 1.5 and 4.5 mg/kg, i.p.) were studied in the open field test. In saline-treated rats both parameters of motor activity were unaffected by ELF-MF irradiation. The rats pre-exposed to ELF-MF and injected with the lowest dose of AMPH showed the same locomotor activity as control animals, while their stereotypic behaviour was significantly elevated. ELF-MF in combination with AMPH at higher doses significantly enhanced motor activity when compared with values obtained in both control and combined experiments with the lowest dose of the drug. However, only combined locomotor effect at the middle dose of AMPH was significantly greater than those observed in corresponding experiments with AMPH alone. These results demonstrate that acute short-term exposure to ELF-MF is able to modify a motor activity in dependence on the extent of AMPH-induced neurotransmitter imbalance.

The effect of amphetamine on Kamin blocking and overshadowing.

Schizophrenic patients show deficits on stimulus salience tasks such as latent inhibition and blocking, which measure the ability to disregard irrelevant stimuli. Amphetamine-treated animals show similar deficits in analogous tasks, thereby providing a model of the stimulus-selection deficits observed in schizophrenia. In two experiments, the effect of the indirect dopamine (DA) agonist D-amphetamine sulphate (1.0 mg/kg, i.p.) on Kamin blocking and overshadowing were examined and compared, in the rat, using the conditioned lick suppression procedure. The aim was to provide some insight into the behavioural and pharmacological mechanisms underlying amphetamine effects in both paradigms. In experiment 1, it was shown that amphetamine selectively disrupted Kamin blocking, when given either at stage 2 alone, or at both stages of the task. In experiment 2, amphetamine treatment significantly abolished Kamin blocking and overshadowing, when administered prior to compound conditioning in both tasks. These data suggest that dopamine may play a critical role in mediating performance in tasks measuring stimulus salience processes. The results are discussed in the framework of the role of DA in stimulus-selection performance.

Effects on weight change of switching from olanzapine to quetiapine

Rats were trained to discriminate the stimulus properties of 1 mg/kg of d-amphetamine sulphate (AMPH) from saline in a two-lever task in which correct responding was reinforced with water under a fixed ratio (FR 32) schedule. Classical antipsychotic drugs from different chemical classes were all able to block the AMPH cue. Doses (mg/kg) inhibiting the cueing effect to 50% (ID50) were 0.035 (haloperidol), 0.04 (spiroperidol), 0.09 (cis(Z)-flupenthixol), 0.12 (trifluperazine), 0.15 (perphenazine), 0.92 (chlorpromazine) and 1.40 (pimozide). The AMPH cue was also antagonized by antipsychotic drugs that are considered atypical due to their relative lack of activity in conventional animal models or inability to produce extrapyramidal symptoms in the clinic. The following ID50 values were obtained: 0.88 (molindone), 1.22 (clozapine), 5.48 (metoclopramide), 15.4 (thioridazine) and 52.8 ((−)-sulpiride). In addition, the AMPH cue was blocked by the D-1 selective dopamine (DA) antagonist, SCH 23390 (ID50 = 0.014 mg/kg). The abilities of these drugs to block the AMPH cue were unrelated to the drugs' effect upon the rate of responding. For example, some drugs (e.g. haloperidol, spiroperidol and SCH 23390) blocked the AMPH cue completely without any effect on the response rate. Furthermore, the non-antipsychotic phenothiazine promethazine (2.5–12.5 mg/kg) failed to affect the AMPH cue although the drug strongly suppressed the response rate. However, the potent DA agonists, apomorphine (0.05–0.33 mg/kg) and lisuride (0.02–0.08 mg/kg), and the DA and norepinephrine agonist, DPI (0.4 and 0.8 mg/kg), did not mimic the AMPH cue or did so only partially. These results suggest that the 1 mg/kg AMPH cue depends on (DA) systems other than those involved in the stereotyped motor behavior commonly produced by high doses of AMPH or DA agonists. Low-dose AMPH discrimination may thus serve as a new model for studying antipsychotic drug action.

Age-related differences in MK-801- and amphetamine-induced locomotor and stereotypic activities of rats

Changes in locomotor and stereotypic activities induced by an i.p. injection of either (+)-5-methyl-10,11-dihydro-5 H-dibenzo( a, d)-cycloheptan-5,10-imine maleate (dizocilpine or MK-801; 0.3 mg/kg) or d-amphetamine sulfate (AMPH; 1.5 mg/kg) were studied in male Mill Hill hooded rats of different age. The following age groups of animals were considered: 28–30 postnatal day (PND)-old rats (peripubertal), 48–50 PND-old (pubertal), 3-month-old (adults), 12-month-old (middle-aged) and 24-month-old (aged). The motor response was measured by an automated animal activity measuring system. The obtained results showed that: (1) in contrast to AMPH, MK-801 induced more pronounced increases of both locomotor and stereotypic activities in peripubertal and pubertal than in adult and aged rats; (2) AMPH induced the same locomotor and stereotypic activity increase in pubertal, adult and middle-aged rats; (3) both AMPH and MK-801 led to a senescence-related decrease of motor activity. These data suggest that the balance of the glutamatergic and dopaminergic systems changes during aging. Such a change is important in understanding schizophrenia and the motor system decline observed in the later stages of life.

Amphetamine enhances Ca 2+ entry and catecholamine release via nicotinic receptor activation in bovine adrenal chromaffin cells

Amphetamine, a psychostimulant, has been shown to act as a channel blocker of muscle nicotinic receptors and to induce a Ca 2+-dependent secretion from adrenal chromaffin cells. In this study, the relationship between amphetamine and nicotinic receptors was studied using bovine adrenal chromaffin cells as a model system. Our results show that d-amphetamine sulfate alone induced an increase in the cytosolic Ca 2+ concentration ([Ca 2+] c) and [ 3H]norepinephrine release in a dose-dependent and extracellular Ca 2+-dependent manner. Two common nicotinic receptor antagonists, hexamethonium and mecamylamine, suppressed the d-amphetamine sulfate-induced [Ca 2+] c rise and [ 3H]norepinephrine release. In addition, d-amphetamine sulfate inhibited the 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP)-induced [Ca 2+] c rise and [ 3H]norepinephrine release, but not the high K +- or veratridine-induced [Ca 2+] c increase and [ 3H]norepinephrine release. Antagonists, including α-bungarotoxin and choline, that are more specific for α7 nicotinic receptors were capable of inhibiting the d-amphetamine sulfate-induced [Ca 2+] c rise, while d-amphetamine sulfate was found to be capable of inhibiting the [Ca 2+] c rise induced by the α7-nicotinic receptor agonists, epibatidine and choline. Moreover, d-amphetamine sulfate dose-dependently suppressed [ 3H]nicotine binding to chromaffin cells. We, therefore, conclude that d-amphetamine sulfate acts as a nicotinic receptor agonist to induce [Ca 2+] c increase and [ 3H]norepinephrine release in bovine adrenal chromaffin cells.

Dopamine receptor blockade in the rat medial prefrontal cortex reduces spontaneous and amphetamine-induced activity and does not affect prepulse inhibition.

The functions and interactions of cortical and subcortical dopamine systems are of interest because alterations in these systems have been implicated in neuropsychiatric diseases, such as schizophrenia. It has been proposed that prefrontal dopamine transmission may oppose dopamine transmission in subcortical sites, such as the nucleus accumbens. Accordingly, reduced prefrontal dopamine transmission would be expected to enhance or induce behavioral effects that have been associated with stimulation of accumbal dopamine receptors. In rats, spontaneous and amphetamine-induced activity is supported by dopamine receptor stimulation in the nucleus accumbens, while prepulse inhibition (PPI) of the acoustic startle response, which is used to measure sensorimotor gating and is disrupted in schizophrenia, is reduced by increased accumbal dopamine receptor stimulation. In the present experiments, we found that bilateral infusion of the dopamine D1/D2 receptor antagonist cis-flupenthixol dihydrochloride into the medial prefrontal cortex of Wistar rats (25 microg each side) reduced spontaneous activity and completely blocked induction of hyperactivity by systemic administration of D-amphetamine sulfate (1 mg/kg), while not affecting PPI. These findings do not support an antagonism between prefrontal and accumbal dopamine in the control of behavior. Rather, our data demonstrate that prefrontal dopamine transmission may modulate some behavioral processes in a similar way to accumbal dopamine.

Effect of amphetamine and phencyclidine on DNA-binding activities of serum response and dyad symmetry elements

Acute administration of d-amphetamine sulphate (AMPH) and (1-[1-phenylcyclohexyl]piperidine hydrochloride) (phencyclidine; PCP) produces a characteristic spatio-temporal distribution of c-Fos protein in the brain. As transcriptional mechanisms underlying the induction of c-fos gene expression may be regulated in a stimulus-specific manner, we have analyzed the binding activities of serum response element (SRE), dyad symmetry element (DSE) and calcium response element (CRE), the major regulatory sites of the c-fos promoter. Electrophoretic mobility shift showed that SRE binding activity was increased for 50–60%, 2–6 h after AMPH, while treatment with PCP resulted in light decrease of SRE binding activity throughout the same time period. Co-administration of AMPH and PCP induced gradual increase of SRE binding activity, reaching maximum (86%) at 6 h. Binding of nuclear proteins to DSE sequence was increased 1–2 h after administration of AMPH (72–87%) and remained elevated till the end of the time window observed. PCP and AMPH/PCP caused different temporal profile of DSE binding with peak (40–54%) 4–6 h after administration. In contrast, DNA-binding activity of the CRE sequences remained unchanged throughout the time period of 6 h under all conditions. Finally, supershift analysis clearly demonstrated presence of SRF and c-Fos protein in the transcriptional complexes bound to SRE and DSE sequences irrespective to AMPH, PCP or combined treatment. These findings also showed that the presence of c-Fos protein in SRE and DSE nucleocomplex support the hypothesis concerning autoregulation of c-fos gene expression during psychostimulant action in vivo.

Intravenous self-administration of amphetamine is increased in a rat model of depression.

Affective disorders and substance abuse frequently coexist, yet few previous studies have examined drug self-administration using animal models of depression. The olfactory-bulbectomized rat is a well-established model that exhibits a high degree of neurochemical similarity to depression. Olfactory bulbectomy (OBX) increases dopamine receptor densities in the ventral striatum, which may increase the reinforcing effects of drugs of abuse. Experiments were designed to test the hypotheses that acquisition and stable self-administration of amphetamine would be increased in bulbectomized rats. In the first experiment, rats underwent bilateral OBX or sham surgery and intravenous jugular catheters were implanted 12-14 days later. Acquisition was examined using a standard operant paradigm involving a nose-poke response for a very low dose of D-amphetamine sulfate (12 microg/infusion, IV). A separate group of rats received coinfusions of sulpiride. In a second experiment designed to minimize differences in acquisition and examine stable self-administration, lever pressing for a low (0.10 mg/kg, IV) or high (0.25 mg/kg, IV) dose of D-amphetamine sulfate was measured in rats pretrained to lever press for food. Bulbectomized rats acquired the self-administration of very low dose amphetamine faster than sham-operated rats and this effect was reversed by sulpiride coinfusion. Stable self-administration of the low dose of amphetamine was also markedly increased in bulbectomized rats. The findings reveal the utility of the OBX model for studying the neurobiological basis of depression and drug abuse comorbidity and support the hypothesis that neurochemical abnormalities associated with depression may enhance the addictive properties of some drugs of abuse.

Hydrogen peroxide production in mouse tissues after acute d-amphetamine administration. Influence of monoamine oxidase inhibition.

The toxicity of amphetamines is conditioned by a complex array of mechanisms, involving the increase of neurotransmission (e.g. leading to hyperthermia) and enzymatic and non-enzymatic oxidation of amphetamines and biogenic amines. Considering that all these processes may increase the generation of hydrogen peroxide (H2O2) by metabolic or non-metabolic redox pathways, the main objective of this work was to evaluate d-amphetamine-induced H2O2 production in mice liver, kidney and heart. The contribution of monoamine oxidase (MAO) to H2O2 production after d-amphetamine administration was studied using the MAO inhibitor pargyline. H2O2 production was measured indirectly using the catalase-H2O2 complex I irreversible inhibitor 3-amino-1,2,4-triazole (AT). Using this method, the measurement of residual catalase activity following administration of AT permits the monitoring of H2O2 production in vivo. Charles River CD-1 mice (30-35 g body weight) were injected with AT just before the injection of d-amphetamine sulphate (20 mg/kg). d-Amphetamine stimulated the production of H2O2 in all tissues studied, although to different degrees. MAO inhibition by itself led to a remarkable decrease of basal H2O2 production in the kidney and a slight decrease in the liver, although no effect was observed in the heart. d-Amphetamine-induced H2O2 production in the heart and kidney was reduced in MAO-inhibited mice. However, in the liver, H2O2 production was transiently potentiated at 30 min under MAO inhibition. In conclusion, d-amphetamine administration leads to an increase in H2O2 production in mouse liver, kidney and heart, and monoamine oxidase plays an important role in this effect.

Adaptative response of antioxidant enzymes in different areas of rat brain after repeated d-amphetamine administration.

d-Amphetamine has been shown to be a potential brain neurotoxic agent, particularly to dopaminergic neurones. Reactive oxygen species indirectly generated by this drug have been indicated as an important factor in the appearance of neuronal damage but little is known about the adaptations of brain antioxidant systems to its chronic administration. In this study, the activities of several antioxidant enzymes in different areas of rat brain were measured after repeated administration of d-amphetamine sulphate (sc, 20 mg/kg/day, for 14 days), namely glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GRed), catalase, and superoxide dismutase (SOD). When compared to a pair-fed control group, d-amphetamine treatment enhanced the activity of GST in hypothalamus to 167%, GPx in striatum to 127%, in nucleus accumbens to 192%, and in medial prefrontal cortex to 139%, GRed in hypothalamus to 139%, as well as catalase in medial prefrontal cortex to 153%. However, the same comparison revealed a decrease in the activity of GRed in medial pre-frontal cortex by 35%. Food restriction itself reduced GRed activity by 49% and enhanced catalase activity to 271% in nucleus accumbens. The modifications observed for the measured antioxidant enzymes reveal that oxidative stress probably plays a role in the deleterious effects of this drug in CNS and that, in general, the brain areas studied underwent adaptations which provided protection against the continuous administration of the drug.