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PubMed1983

Amphetamine inhibits the electrically evoked release of [3H]dopamine from slices of the rabbit caudate.

The effects of d-amphetamine on the spontaneous and electrically evoked release of [3H]dopamine in slices of the rabbit caudate nucleus were investigated. At a concentration of 0.1 microM amphetamine did not modify the spontaneous outflow of radioactivity, but significantly inhibited the release of [3H]dopamine elicited by electrical stimulation. At a 10-fold higher concentration (1 microM) amphetamine enhanced the spontaneous outflow of radioactivity and also inhibited the stimulation-evoked release of [3H]dopamine. The inhibition by amphetamine of electrically evoked release of [3H]dopamine was also observed under conditions in which monoamine oxidase was inhibited by pargyline. At concentrations of 0.1 and 0.5 microM amphetamine there was no inhibition of neuronal uptake and retention of [3H]dopamine in slices of the rabbit caudate. In the presence of 100 microM l-3-iodotyrosine, the inhibition by amphetamine of [3H]dopamine release was still obtained. The dopamine receptor antagonists, haloperidol and sulpiride, were not able to antagonize the inhibition by amphetamine of the electrically evoked release of [3H] dopamine at concentrations which effectively blocked apomorphine-induced inhibition of stimulation-evoked release of the labeled neurotransmitter. Exposure to serotonin in the presence of an inhibitor of neuronal uptake did not modify the spontaneous outflow of radioactivity or the electrically evoked release of [3H] dopamine. Nomifensine, an inhibitor of neuronal uptake of dopamine prevented the release of [3H]dopamine induced by exposure to 10 microM amphetamine and antagonized the inhibitory effects of lower concentrations of amphetamine on the electrically evoked release of [3H]dopamine. Tyramine and amfonelic acid in low concentrations enhanced the spontaneous outflow of radioactivity and, similarly to amphetamine, inhibited the electrically evoked release of [3H]dopamine. Exposure to bretylium (1 and 10 microM) inhibited the release of [3H]dopamine elicited by electrical stimulation. In the presence of bretylium, the inhibition by amphetamine of the stimulation-evoked release of [3H]dopamine was still present. In contrast to its inhibitory action on the release of [3H]dopamine, exposure to amphetamine (0.1-1.0 microM) enhanced in a concentration-dependent manner the electrically evoked release of [3H]norepinephrine from the rabbit hypothalamus. These results indicate that the inhibition by amphetamine of the electrically evoked release of [3H]dopamine does not involve the activation of presynaptic inhibitory dopamine autoreceptors possibly located on dopaminergic nerve terminals.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphetamine↗
PubMed1986

Tyrosine influence on amphetamine self-administration and brain catecholamines in the rat.

Earlier work had shown that L-tyrosine administration, precursor to both dopamine (DA) and norepinephrine (NE), could increase brain DA metabolite concentrations after amphetamine treatment and restore amphetamine-induced decreases in whole brain NE. Both monoamines have been suggested to participate in some aspects of continued drug abuse. Rats trained to self-administer IV d-amphetamine were treated with IP tyrosine during test sessions to examine the behavioral and neurochemical response. In animals with less than 35 days of amphetamine exposure, L-tyrosine treatments did not alter amphetamine self-administration. Experiments using a computer-controlled injection apparatus which administered IV amphetamine to naive rats in patterns mimicking those of self-administration animals indicated tyrosine could antagonize amphetamine-induced NE depletions. The increases in DA metabolite dihydroxyphenylacetic acid (DOPAC) were found limited to the striatum, an area not involved in the positive reinforcing effects of amphetamine. Concentrations of DOPAC in nucleus accumbens septi were unchanged by the amphetamine or the amphetamine-tyrosine regimen. In rats with 4-6 months of chronic amphetamine exposure, however, L-tyrosine administration significantly reduced daily drug self-injection. While neurochemical responses to tyrosine could not be performed, it is speculated that chronic long-term amphetamine abuse might alter the tyrosine-induced changes in DA and/or NE synthesis and release compared to that in the acute or short-term amphetamine abuse animals. These data suggest that the success or failure of an experimental pharmacologic treatment strategy in psychomotor stimulant abusers might be dependent on the subjects history of drug abuse.

Animals↗
PubMed1992

Selective tolerance to discriminative stimulus effects of morphine or d-amphetamine.

Pharmacological selectivity of tolerance to the discriminative stimulus effects of morphine or d amphetamine was examined in pigeons trained to discriminate among 3.2mg/kg morphine, saline, and 1.8mg/kg d-amphetamine under a 3-key fixed-ratio 30 schedule of food delivery. Cumulative doses of morphine (0.32-10mg/kg) or d-amphetamine (0.10-3.2mg/kg) evoked morphine-or d-amphetamine-key responding, respectively, in a dose-dependent manner. Suspending training and administering repeated doses of morphine (32mg/kg b.i.d.) for 1 week increased the dose of morphine required for morphine-key responding approximately 5-fold, without altering sensitivity to d-amphetamine. Conversely, repeated treatment with d-amphetamine (5.6mg/kg b.i.d.) increased the dose of d-amphetamine required for d-amphetamine-key responding approximately 7-fold, without decreasing sensitivity to morphine. Repeated treatment with saline (1ml/kg b.i.d.) for 1 or 2 weeks did not alter sensitivity to stimulus effects of either morphine or d-amphetamine. Sensitivity to stimulus effects of morphine recovered fully within 1 week after morphine treatment ended; sensitivity to stimulus effects of d-amphetamine recovered partially within 3 days after d-amphetamine treatment ended. For morphine, but not for d-amphetamine, increases in the dose required for stimulus effects were accompanied by increases in the dose required for rate-reducing effects. These results demonstrate that tolerance to discriminative stimulus effects of morphine and d-amphetamine is pharmacologically selective and suggest that pharmacotherapies targeted to one drug of abuse may produce little change in sensitivity to subjective effects of drugs from a different pharmacological class.

Journal Article↗
PubMed1991

NTP Toxicology and Carcinogenesis Studies of dl-Amphetamine Sulfate (CAS No. 60-13-9) in F344/N Rats and B6C3F1 Mice (Feed Studies).

dl-Amphetamine sulfate is used for the treatment of narcolepsy in adults and behavioral syndromes in children. Toxicology and carcinogenesis studies were conducted by administering dl-amphetamine sulfate (USP grade) in feed to groups of F344/N rats and B6C3F1 mice of each sex for 14 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Chinese hamster ovary (CHO) cells. 14-Day Studies: The chemical was administered at dietary concentrations of 0, 47, 94, 188, 375, or 750 ppm for rats and 0, 125, 250, 500, 1,000, or 2,000 ppm for mice. Decreased body weight gain was seen at the higher concentrations, but no chemical-related deaths or toxic lesions were observed. 13-Week Studies: The chemical was administered at dietary concentrations of 0, 47, 94, 188, 375, or 750 ppm for rats and 0, 125, 250, 500, 1,000, or 2,000 ppm for mice. None of the rats died, but 6/10 male mice and 7/10 female mice that received 2,000 ppm, 3/10 male mice that received 1,000 ppm, and 8/10 male mice that received 500 ppm died before the end of the studies. Decreased body weight gain and hyperactivity were seen in dosed rats and mice. Final body weights of rats receiving 188 ppm or more were 62% to 89% those of controls, and final body weights of mice receiving 250 ppm or more were 70% to 86% those of controls. There were no lesions that were considered to be a primary effect of the chemical. Based on decreased body weight gain and hyperactivity in the 13-week studies, 2-year studies were conducted by feeding diets containing 0, 20 or 100 ppm dl-amphetamine sulfate to groups of 50 rats or 50 mice of each sex. Body Weights and Survival in the 2-Year Studies: No significant differences in survival were observed between any groups of rats or mice (male rats: control, 30/50; low dose, 31/50; high dose, 33/50; female rats: 33/50; 42/50; 37/50; male mice: 48/50; 48/50; 49/50; female mice: 35/50; 36/50; 44/50). Final body weights of dosed rats and mice were decreased relative to those of controls. Final body weights were 92% and 86% those of controls for low- and high-dose male rats, 89% and 70% those of controls for low- and high-dose female rats, 85% and 72% those of controls for low- and high-dose male mice, and 81% and 66% those of controls for low- and high-dose female mice. Hyperactivity was observed in all dosed groups. Feed consumption was similar among control and exposed groups with the exception of high-dose female rats (84% of controls) and high-dose male mice, for which hyperactivity resulted in scattering of feed and overestimation of feed consumption. The average amount of dl-amphetamine sulfate consumed per day was estimated to be 1 or 5 mg/kg for low- and high-dose rats, 4 or 30 mg/kg for low- or high-dose male mice, and 3 or 19 mg/kg for low- or high-dose female mice. Nonneoplastic and Neoplastic Effects in the 2-Year Studies: Myelofibrosis, cataracts, and retinal atrophy in female rats, and ovarian atrophy in female mice occurred in a larger proportion of high-dose animals than in controls. Dose-related increases in neoplasms did not occur in rats or mice receiving amphetamine. The administration of dl-amphetamine sulfate was associated with decreases in the incidence of total neoplasms and in the incidences of certain site-specific neoplasms, including pheochromocytomas of the adrenal gland in male rats (23/49, 15/44, 7/50), fibroadenomas of the mammary gland in female rats (21/50, 11/50, 2/50), adenomas of the anterior pituitary gland in male and female rats and female mice (male rats: 15/49, 15/48, 9/49; female rats: 31/50, 24/48, 19/50; female mice: 12/49, 6/49, 1/46), endometrial stromal polyps of the uterus of female rats (10/50, 6/50, 3/50), adenomas or carcinomas (combined) of the liver in male and female mice (male: 14/50, 12/50, 2/50; female: 5/50, 1/50, 1/47), adenomas of the harderian gland in male and female mice (male: 4/50, 2/50, 0/50; female: 5/50, 2/50, 0/47), and adenomas or carcinomas (combined) of the lung in male and female mice (male: 8/50, 3/50, 4/50; female: 8/50, 6/50 (combined) of the lung in male and female mice (male: 8/50, 3/50, 4/50; female: 8/50, 6/50, 1/47). Genetic Toxicology: dl-Amphetamine sulfate was tested for induction of gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 with and without exogenous metabolic activation (S9); the only response observed was in strain TA98 in the presence of S9, and it was judged to be equivocal. No induction of sister chromatid exchanges or chromosomal aberrations occurred in Chinese hamster ovary cells treated with amphetamine sulfate in either the presence or the absence of S9. Conclusions: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of dl-amphetamine sulfate for male or female F344/N rats or male or female B6C3F1 mice fed 20 or 100 ppm. The administration of dl-amphetamine sulfate was associated with decreased body weight. There were decreased incidences of total neoplasms in dosed rats and mice, of adrenal pheochromocytomas in male rats, of mammary gland fibroadenomas and uterine polyps in female rats, of pituitary gland adenomas in male and female rats and female mice, and of harderian gland adenomas, liver neoplasms, and lung neoplasms in male and female mice. Synonyms: (±)-amphetamine sulfate; (±)-2-amino-1-phenylpropane sulfate; amphetamine sulfate; deoxynorephedrine; desoxynorephedrine; (±)-a-methylphenethylamine sulfate; (±)-phenisopropylamine sulfate; b-phenyl isopropylamine Trade Names: Acedron; Adipan; Adiparthrol; Aketdrin; Aktedrin; Alentol; Amfetamina; Amphaetamin; Amphamed; Amphatamin; Amphate; Amphedrine; Amphetaminum; Amphezamin; Amphoids-S; Anara; Anfetamina; Anorexine; Astedin; Benzafinyl; Benzamphetamine; Benzebar; Benzedrina; Benzedryna; Benzolone; Benzpropamine;Betafen; Betaphen; Bluzedrin; Centramina; Didrex; Dietamine; Durophet; Elastonin; Elastonon; Euphobine; Euphodine; Euphodyn; Fabedrine; Fenamin; Fenara; Fenedrin; Fenopromin; Halloo-Wach; Ibiozedrine; Isamin; Isoamin; Isoamyne; Isomyn; Leodrin; Levonor; Linampheta; Mecodrin; Mimetina; Monetamine; Noclon; Norephedrane; Norphedrane; Novydrine; Oktedrin; Oraldrina; Ortenal; Orthedrin; Percomon; Pharmamedrine; Pharmedrine; Phenamine; Phenedrine; Phenopromin; Phenpromin; Profamina; Profetamine; Propenyl; Propisamine; Psychedrine; Psychedryna; Psychedrinum; Psychoton; Racephen; Rhinalator; Sedolin; Simpamina; Simpamine; Simpatedrin; Stimulan; Sympametin; Sympamine; Sympatedrine; Synsatedrine; Theptine; Vapedrine; Weckamine; Zedrine Slang for Amphetamines: bennies; benzies; cartwheels; hearts; peaches; roses

Journal Article↗
PubMed2002

Compartment-specific changes in striatal neuronal activity during expression of amphetamine sensitization are the result of drug hypersensitivity.

Repeated exposure to drugs of abuse induces behavioural sensitization, i.e. a persistent hypersensitivity to the psychomotor stimulant effects of these drugs. This may be the result of increased responsiveness, to drugs, of mesostriatal dopamine systems and their projections, but it has also been suggested that acute and sensitized behavioural responses to psychostimulant drugs involve activation of distinct neuronal circuits. In order to distinguish between these possibilities, we studied amphetamine-induced c-fos immunoreactivity in subregions of rat striatum (patch and matrix compartments of caudate-putamen and nucleus accumbens core and shell) in drug-naive rats, as well as during long-term expression of amphetamine sensitization. We found that, in sensitized animals, amphetamine (1.0 mg/kg) evoked an increase in the ratio of c-fos-immunopositive cells in striatal patch and matrix compartments, suggesting a preferential involvement of striatal patches in the sensitized response to amphetamine. In drug-naive rats, amphetamine (0.5-5.0 mg/kg) dose-dependently increased c-fos expression in all striatal subregions. Remarkably, the highest dose of amphetamine also evoked an increase in patch : matrix ratio of c-fos immunoreactivity. In nucleus accumbens core and shell of amphetamine- and saline-pretreated animals, amphetamine (1.0 mg/kg) evoked comparable increases in c-fos expression. These data indicate that distinct striatal compartments display a differential sensitivity to amphetamine in both drug-naive and amphetamine-sensitized animals. In addition, they suggest that the shift in amphetamine-induced c-fos expression from striatal matrix to patches in sensitized animals is the consequence of a change in the sensitivity to amphetamine, rather than a long-term circuitry reorganization that is exclusive to the sensitized state.

Amphetamine↗
PubMed1996

Detection of amphetamine following administration of fenproporex.

Drugs that are metabolized to amphetamine or methamphetamine are potentially significant concerns in the interpretation of amphetamine-positive drug testing results. A number of different compounds have been reported to produce amphetamine in the urine of users. One of these compounds, fenproporex, has been shown to produce amphetamine. Previous reports indicate that the parent compound can be detected only for a few hours following administration, whereas the amphetamine can be detected for several days. Administration of fenproporex to five healthy volunteers resulted in amphetamine being detected in the urine of all subjects. Peak concentrations of amphetamine were detected at approximately 6-20 h postdose and ranged from approximately 1200 to 2100 ng/mL amphetamine. Amphetamine could be detected (> 5 ng/mL) in the urine for up to 119 h. Analysis of the metabolically produced amphetamine showed the presence of both enantiomers, which can be helpful in the differentiation of some illicit amphetamine use from the use of this precursor drug. More significantly, all samples that contained amphetamine at a concentration of at least 500 ng/mL were shown to also contain measurable amounts of the parent compound.

Administration, Oral↗
PubMed2004

Mechanisms underlying the effects of amphetamine on particulate PKC activity.

Amphetamine stimulates particulate protein kinase C (PKC) activity that is associated with the outward-transport of dopamine (DA) (Giambalvo [2003] Synapse 49:125-133). This stimulatory effect requires intracellular calcium ([Ca](i)) and endogenous DA and when DA release is diminished, the inward-transport of amphetamine inhibits PKC activity. This study examines the mechanisms involved. It was found that synaptoneurosomes incubated with amphetamine showed a dose-dependent increase in phospholipase C and A(2) activities. Furthermore, pretreatments with the phospholipase C inhibitor D609 or the phospholipase A(2) inhibitors quinacrine or p-bromophenacylbromide attenuated the amphetamine-induced increase in PKC activity. This suggests that both phospholipases were essential for the amphetamine-induced increase in PKC activity. The Na/Ca antiporter was also involved, since pretreatment with amiloride or benzamil attenuated the amphetamine-induced increase in PKC activity. Since these drugs by themselves increased PKC activity, the return to basal activity after addition of amphetamine suggests that, in the absence of Na/Ca exchange, amphetamine had an inhibitory effect on PKC activity. This inhibitory effect might be due to the activation of phospholipase A(2) through an increase in intracellular pH induced by amphetamine. This was supported by the finding that pretreatment with dimethylamiloride, an inhibitor of the Na/H antiporter that increases intracellular [H(+)], attenuated the effects of amphetamine on PKC activity. Other drugs that decrease intracellular [H(+)] (ammonia, monensin) also inhibited PKC activity without Ca. In contrast to amphetamine, monensin had no effect on PKC activity with Ca. This could be related to its large differential effects on phospholipase A(2) vs. phospholipase C activity. Thus, the monensin-mediated decrease in PKC activity seen without Ca was partially attenuated by pretreatment with quinacrine. Furthermore, when Na/Ca antiporter was inhibited with benzamil, monensin inhibited PKC activity. These results suggest that amphetamine, as well as monensin, may have dual effects on PKC activity, a Ca-dependent stimulatory effect via phospholipase C, and an inhibitory effect via phospholipase A(2).

Ammonia↗
PubMed2001

Role of D1-like receptors in amphetamine-induced behavioral sensitization: a study using D1A receptor knockout mice.

RATIONALE: The role played by D(1)-like receptors in amphetamine-induced behavioral sensitization has been examined using both the D(1)-like receptor antagonist, SCH 23390, and the D(1A) receptor knockout mouse (i.e. D(1A)-deficient mice). Studies using these two approaches have provided conflicting evidence about the importance of D(1)-like receptors for amphetamine-induced behavioral sensitization. OBJECTIVE: The purpose of the present study was to determine: (a) whether D(1A)-deficient mice exhibit amphetamine-induced locomotor sensitization after 3 and 17 drug abstinence days, and (b) whether SCH 23390, which binds to both D(1A) and D(1B) receptor subtypes, blocks development of amphetamine sensitization in wild-type and D(1A)-deficient mice. METHODS: In the first experiment, adult wild-type and D(1A)-deficient mice were injected with amphetamine (0, 1, 2, 4, or 8 mg/kg, IP) for 7 consecutive days. In the second experiment, wild-type and D(1A)-deficient mice were pretreated with SCH 23390 (0, 0.15, or 0.5 mg/kg, IP) 30 min prior to being injected with amphetamine (0 or 8 mg/kg, IP). After each daily amphetamine injection, mice were placed in activity chambers where distance traveled (i.e. horizontal locomotor activity) was measured for 60 min. On the test days, which occurred after 3 or 17 drug abstinence days, mice were injected with 1 mg/kg amphetamine and locomotion was measured for 120 min. RESULTS: Both wild-type and D(1A)-deficient mice exhibited amphetamine-induced locomotor sensitization. Pretreatment with 0.5 mg/kg SCH 23390 blocked the development of locomotor sensitization in wild-type mice, but did not alter the sensitized responding of D(1A)-deficient mice. CONCLUSIONS: It appears that D(1)-like receptors are necessary for the development of amphetamine sensitization in wild-type mice, while neither the D(1A) nor D(1B) receptor subtypes are necessary for the amphetamine-induced locomotor sensitization of D(1A)-deficient mice. A possible explanation for these conflicting results is that D(1A)-deficient mice may have a compensatory mechanism (not involving D(1B) receptors) that allows them to exhibit amphetamine-induced behavioral sensitization in the absence of the D(1A) receptor.

Amphetamine↗
PubMed1999

The effect of previous exposure to amphetamine on drug-induced locomotion and self-administration of a low dose of the drug.

RATIONALE AND OBJECTIVES: In order to assess directly the relationship between locomotor activity and drug self-administration, the present experiment simultaneously measured these two behaviors in rats with different histories of pre-exposure to amphetamine either following or in the absence of priming injections of the drug. METHODS: Different groups of rats were exposed to ten daily injections of either saline (1.0 ml/kg, i.p.) or amphetamine (1.5 mg/kg, i.p.) and, in each of 13 daily sessions starting 10 days later, were given the opportunity to lever press for a low dose of amphetamine (10 microg/kg per i.v. infusion) in a two-lever (active versus inactive) continuous reinforcement task. Animals were administered a priming injection of amphetamine (1.0 mg/kg, i.p.) immediately before testing on the first 8 days, a saline injection (1.0 ml/kg, i.p.) on the next 3 days and amphetamine on the final 2 days of testing. RESULTS: Consistent with previous reports, prior exposure to amphetamine led to an enhanced locomotor response to the priming injection of amphetamine on the first day of testing. Little pressing for drug was observed on this day. Following priming injections on the subsequent test days, evidence for enhanced locomotion by amphetamine-pre-exposed rats diminished and both groups showed comparable and progressive increases in active versus inactive lever pressing. When priming injections were not made, however, only animals previously exposed to amphetamine maintained lever pressing for the drug. Under these conditions, these animals emitted more active lever presses and time-out responses and exhibited higher levels of locomotor activation in proximity to the active drug administering lever than did saline-pre-exposed rats. CONCLUSIONS: These results are consistent with the view that previous exposure to amphetamine produces a long-lasting enhancement in the behavioral activation animals will direct toward stimuli associated with the drug. This enhancement was displayed initially as a sensitized locomotor response to amphetamine on the first day of testing and was subsequently observed on those test days when no priming injections were given when animals continued to self-administer a low dose of amphetamine under a simple schedule of reinforcement. The implications of these findings for our understanding of the excessive expression of drug-directed behaviors are discussed.

Amphetamine↗
PubMed1982

Further studies on the long-term depletion of striatal dopamine in iprindole-treated rats by amphetamine.

(+) Amphetamine was more potent (-) amphetamine in causing persistent depletion of striatal dopamine in iprindole-treated rats. This effect of amphetamine was not mimicked by EXP561, a structurally related compound that is more potent than amphetamine as an inhibitor of dopamine uptake. The depletion of striatal dopamine at 1 week after amphetamine injection in iprindole-treated rats was prevented by amfonelic acid, an inhibitor of uptake into dopamine neurons. The depletion of dopamine by amphetamine was prevented when amfonelic acid was given at the same time as amphetamine or as long as 4 hr after amphetamine but not when amfonelic acid was given 24-48 hr after amphetamine. Amfonelic acid antagonized the depletion of dopamine by amphetamine but not the depletion of serotonin by p-chloroamphetamine; fluoxetine antagonized the depletion of serotonin by p-chloroamphetamine but not the depletion of dopamine by amphetamine. Pretreatment with alpha-methyl-tyrosine to block dopamine synthesis antagonized the persistent depletion of dopamine by amphetamine, but pretreatment with an inhibitor of monoamine oxidase to increase that dopamine concentration had no effect. The possibility that prolonged release of dopamine from intraneuronal storage granules leads to deleterious effects on dopamine neurons is discussed.

Amphetamines↗
PubMed1983

Nisoxetine and amphetamine share discriminative stimulus properties in mice.

The interaction of amphetamine with noradrenergic neurons could mediate a portion of the drug's discriminative stimulus properties. To test this hypothesis, mice were trained to discriminate 1.0 or 3.2 mg/kg amphetamine, 32 mg/kg of the selective norepinephrine uptake inhibitor, nisoxetine, or 32 mg/kg nisoxetine + 1.0 mg/kg amphetamine from saline. Differential drug- or saline-appropriate responding was determined using a two photocell-beam procedure with beam interruption as the operant. Reinforcement (5-sec access to evaporated milk) was presented on a fixed-ratio 20 (FR-20) schedule. Mice trained to discriminate 1.0 mg/kg amphetamine from saline generalized to nisoxetine (32 mg/kg) alone and to doses of 0.56 mg/kg amphetamine and above but not to lower doses unless pretreated with nisoxetine (20 or 32 mg/kg). Mice trained to discriminate nisoxetine (32 mg/kg) from saline generalized to 0.56, 1.0 and 3.2 mg/kg amphetamine and generalized to all amphetamine doses when pretreated with nisoxetine (32 mg/kg). Mice trained to discriminate the drug combination from saline generalized to nisoxetine (32 mg/kg) alone, and to 3.2 mg/kg amphetamine tested alone, to 0.56 mg/kg of amphetamine or above when the lower dose of nisoxetine (20 mg/kg) was used, and to all test doses of amphetamine with nisoxetine (32 mg/kg) pretreatment. Mice trained to discriminate 3.2 mg/kg amphetamine from saline generalized to no test dose of amphetamine following either saline or nisoxetine (32 mg/kg) pretreatment. Testing with several doses of pentobarbital (1.0, 3.0, 10.0 and 18.0 mg/kg) resulted in saline-appropriate responding regardless of training group.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗
PubMed1995

Repeated amphetamine administration induces a prolonged augmentation of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in rat striatum.

Semi-quantitative immunocytochemistry was used to investigate the levels of cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos and Fos-related antigen immunoreactivity in the striatum of rats after acute or repeated amphetamine administration. Rats were perfused 20 min (phosphorylated cyclase response element-binding protein) or 2 h (cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos, Fos-related antigen) after a single injection (5 mg/kg, i.p.) or five daily injections of amphetamine. The latency to onset of stereotypical behaviors was significantly reduced in rats exposed to repeated amphetamine as compared to acute amphetamine, indicating development of behavioral sensitization. Cyclase response element-binding protein immunoreactivity was not altered in the dorsal or ventral striatum following acute or repeated amphetamine. Phosphorylated cyclase response element-binding protein immunoreactivity was significantly induced 20 min, but not 2 h, following acute amphetamine, whereas a significant induction of phosphorylated cyclase response element-binding protein immunoreactivity was found 20 min and 2 h after repeated amphetamine in the dorsal striatum only. Fos immunoreactivity was significantly induced in the dorsal striatum following acute and repeated amphetamine. Fos immunoreactivity in the core of the nucleus accumbens was significantly increased following repeated amphetamine only. Acute amphetamine induced, and repeated amphetamine further augmented, Fos-related antigen immunoreactivity in the dorsal striatum, while not affecting Fos-related antigen immunoreactivity in the nucleus accumbens. These data demonstrate that repeated amphetamine administration results in a prolonged induction of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in the dorsal striatum, indicating that alterations in striatal gene expression associated with the development of behavioral sensitization may be mediated, in part, by these transcription factors.

Amphetamine↗
PubMed2003

Amphetamine modulation of paced mating behavior.

The present study evaluated the effects of acute and repeated, intermittent amphetamine administration on paced mating behavior in ovariectomized (OVX) rats primed with estrogen and progesterone. In Experiment 1, female rats were tested for paced mating behavior following acute administration of amphetamine (1.0 mg/kg). Amphetamine increased the likelihood that a female would withdraw from a male following a mount or an intromission. Although this dose of amphetamine did not alter sexual receptivity or the latency to return to a male after sexual stimulation, locomotor activity was increased significantly. Experiment 2 evaluated the dose response characteristics of acute amphetamine (0.5, 1.0 and 2.0 mg/kg) administration on paced mating behavior. In agreement with Experiment 1, amphetamine at all doses increased the likelihood that a female would withdraw from a male following sexual stimulation. In Experiment 3, female rats were tested for partner preference (sexually active male vs. estrous female) following acute amphetamine administration. Amphetamine treatment augmented both social and sexual preferences. In Experiment 4, female rats were administered estrogen (20 microg/kg) and amphetamine (1.0 mg/kg) for 3 weeks and tested for paced mating behavior 1 and 4 weeks later, amphetamine free. Repeated intermittent exposure to amphetamine shortened the latency to return to a male after receiving a mount on the test conducted 1 week after the final drug injections. Collectively, these results suggest that the acute effects of amphetamine on paced mating behavior may reflect a reduction in social and sexual behaviors and an increase in locomotor activity, whereas the effects of repeated exposure may reflect a change in incentive motivation.

Amphetamine↗
PubMed1998

D1 and D2 dopamine receptor mediation of amphetamine-induced acetylcholine release in nucleus accumbens.

To assess the interaction of dopamine and acetylcholine systems in the rat nucleus accumbens in response to direct D-amphetamine administration, in vivo microdialysis measures of acetylcholine were used during reverse dialysis of amphetamine alone and in combination with D1 and D2 receptor antagonists SCH 23390 and sulpiride, respectively. During a 15-min exposure to amphetamine (50 microM) in the nucleus accumbens, acetylcholine increased to 33% above pre-infusion levels, became maximal at 15 min post-infusion (+41%) and gradually returned to baseline levels by 60 min post-amphetamine. Conversely, amphetamine (1 mM) administration caused a biphasic change in acetylcholine release with a trend toward a decrease (-14%) during exposure followed by a significant increase (+36%) at 30 min post-amphetamine that returned to baseline levels by 60 min after infusion. The increases observed during amphetamine (50 microM) exposure and during recovery from amphetamine (1 mM) were both blocked by co-administration with the D1 antagonist, SCH 23390 (10 microM), but not with the D2 antagonist, sulpiride (10 microM). Co-infusion of sulpiride eliminated the trend toward reduced acetylcholine release observed during 1 mM amphetamine whereas co-administration of SCH 23390 potentiated this decrease. A possible tonic D1 facilitation of nucleus accumbens acetylcholine release was indicated by the consistent reductions in acetylcholine release observed during infusion of SCH 23390. These results suggest that amphetamine administration in the nucleus accumbens induces a bidirectional change in acetylcholine release that is dependent on dose and opposing effects of nucleus accumbens D1 and D2 activation. In general, relatively low doses of amphetamine administered into the nucleus accumbens caused an increase in acetylcholine release that was dependent on dopamine D1 receptors whereas higher doses of amphetamine resulted in a D2-mediated decrease.

Acetylcholine↗
PubMed2005

Brief cognitive behavioural interventions for regular amphetamine users: a step in the right direction.

AIMS: The present study sought to replicate and extend a small pilot study conducted by Baker, Boggs & Lewin (2001) which demonstrated that brief interventions consisting of motivational interviewing and cognitive-behaviour therapy (CBT) were feasible and associated with better outcomes compared with a control condition. DESIGN: Randomized controlled trial (RCT). SETTING: Greater Brisbane Region of Queensland and Newcastle, NSW, Australia. PARTICIPANTS: The study was conducted among 214 regular amphetamine users. MEASUREMENTS: Demographic characteristics, past and present alcohol and other drug use and mental health, treatment, amphetamine-related harms and severity of dependence. FINDINGS: The main finding of this study was that there was a significant increase in the likelihood of abstinence from amphetamines among those receiving two or more treatment sessions. In addition, the number of treatment sessions attended had a significant short-term beneficial effect on level of depression. There were no intervention effects on any other variables (HIV risk-taking, crime, social functioning and health). Overall, there was a marked reduction in amphetamine use among this sample over time and, apart from abstinence rates and short-term effects on depression level, this was not differential by treatment group. Reduction in amphetamine use was accompanied by significant improvements in stage of change, benzodiazepine use, tobacco smoking, polydrug use, injecting risk-taking behaviour, criminal activity level, and psychiatric distress and depression level. CONCLUSIONS: A stepped-care approach is recommended. The first step in providing an effective intervention among many regular amphetamine users, particularly those attending non-treatment settings, may include provision of: a structured assessment of amphetamine use and related problems; self-help material; and regular monitoring of amphetamine use and related harms. Regular amphetamine users who present to treatment settings could be offered two sessions of CBT, while people with moderate to severe levels of depression may best be offered four sessions of CBT for amphetamine use from the outset, with further treatment for amphetamine use and/or depression depending on response. Pharmacotherapy and/or longer-term psychotherapy may be suitable for non-responders. An RCT of a stepped-care approach among regular amphetamine users is suggested.

Adult↗
PubMed1999

Transitions between the injection of heroin and amphetamines.

AIMS: To assess in current injecting heroin and amphetamine users to what extent their history of injecting represents a transition from amphetamine to heroin. DESIGN: Cross-sectional survey. SETTING: Sydney, Australia. PARTICIPANTS: One hundred and fifty-one primary heroin injectors and 145 primary amphetamine injectors recruited through advertisements, needle exchanges, methadone maintenance clinics and by word of mouth. FINDINGS: Six major transition patterns were detected: heroin-heroin (n = 61), amphetamines-heroin (n = 60), heroin-amphetamines-heroin (n = 30), amphetamines-amphetamines (n = 80), amphetamines-heroin-amphetamines (n = 41) and heroin-amphetamines (n = 24). A logistic regression analysis predicting presence or absence of a transition from the original primary drug indicated that length of injecting career, years of education and original drug injected were independent predictors. Thus, the longer the injecting career, the greater the likelihood of a transition. If the original drug injected was amphetamine, the greater the likelihood of transition; and the more prior years of education, the lower the chances of a transition. CONCLUSIONS: While there was a small preponderance of movement from primary amphetamine injecting to primary heroin injecting, there was also movement in the other direction. Heroin use is not necessarily a stable endpoint for injecting careers.

Adolescent↗
PubMed2002

The effect of amphetamine sensitization on mouse immunoreactivity.

Recent studies indicate a role of the immune system in the behavioral effects of amphetamine in rodents. In the present study we attempted to find a connection between the behavioral changes induced by repeated, intermittent administration of amphetamine and some immunological consequences of sensitization to amphetamine in mice. Male Albino Swiss mice were treated repeatedly (for 5 days) with amphetamine (1 mg/kg, i.p.). On day 9, they received a challenge dose of amphetamine (1 mg/kg). Acute administration of amphetamine increased their locomotor activity by ca. 40%. In animals treated repeatedly with amphetamine, the challenge dose of the psychostimulant induced behavioral sensitization, i.e. the higher locomotor activation as compared with that after its first administration to mice. Immune functions were evaluated by the ability of splenocytes to proliferate and to produce cytokines such as interferon gamma (IFN-gamma), interleukin (IL)-4 and IL-10. Acute amphetamine administration significantly decreased, by ca. 30% and 25%, the proliferation of splenocytes in response to an optimal and a suboptimal dose of concanavalin A (Con A), respectively, and increased their ability to produce IL-4. Chronic intermittent treatment with amphetamine significantly decreased, by ca. 65% and 50%, the proliferative response of T cells to an optimal and a suboptimal dose of Con A, respectively, and diminished by 20% the metabolic activity of splenocytes. The above data showed that both acute and chronic amphetamine administration diminished some aspects of the cell-mediated immunity; nevertheless, immunosuppression was particularly evident in amphetamine-sensitized mice. Our findings seem to indicate possible importance of monitoring and correcting immune changes in the therapy of amphetamine addiction.

Amphetamine↗
PubMed1977

On the aromatic hydroxylation of amphetamine in rat liver microsomes and perfused liver preparations: effects of long-term administration.

The liver microsomal p-hydroxylation of amphetamine to parahydroxyamphetamine (pOHA) was dependent on NADP and inhibited by carbon monoxide indicating the involvement of cytochrome P-450, SKF 525-A, fenfluramine and desmethylimipramine were the most effective inhibitors of this pathway of amphetamine metabolism. Repeated administraion of phenobarbital resulted in reduced p-hydroxylation of amphetamine in vitro. Chronic administration of amphetamine reduced the microsomal p-hydroxylation of amphetamine without apparent changes in the cytochrome P-450 levels or in the activity of NADPH-cytochrome c reductase. The aromatic hydroxylation of aniline and the demethylation of ethylmorphine was not affected by this treatment. However, the 455 nm complex formed during the microsomal metabolism of N-hydroxy-amphetamine was increased by the long-term administration of amphetamine. These results indicate some pecularities of the in vitro hydroxylation of amphetamine by rat liver microsomes. Amphetamine disappeared from the perfusate of the perfused liver at the same rate in rats given a single dose of amphetamine and in rats given amphetamine orally for four weeks. The excretion of pOHA and its conjugate increased at 60 and 90 min. and 30, 60 and 90 min. respectively in the perfusate of the same experiment as compared to the controls. The total excretion of radioactive amphetamine metabolites at the end of the perfusion was increased in the perfusate and reduced in the bile compared to the control experiment.

Administration, Oral↗