Repeated exposure of adolescent rats to oral methylphenidate does not induce behavioral sensitization or cross-sensitization to nicotine

Several lines of evidence indicate that the use of stimulant drugs, including methylphenidate (MPD), increases tobacco smoking. This has raised concerns that MPD use during adolescence could facilitate nicotine abuse. Preclinical studies have shown that repeated treatment with an addictive drug produces sensitization to that drug and usually cross-sensitization to other drugs. Behavioral sensitization has been implicated in the development of drug addiction. We examined whether repeated oral MPD administration during adolescence could induce behavioral sensitization to MPD and long-lasting cross-sensitization to nicotine. Adolescent male Wistar rats were treated orally with 10 mg/kg MPD or saline (SAL) from postnatal day (PND) 27 to 33. To evaluate behavioral sensitization to MPD in adolescent rats (PND 39), the SAL pretreated group was subdivided into two groups that received intragastric SAL (1.0 mL/kg) or MPD (10 mg/kg); MPD pretreated rats received MPD (10 mg/kg). Cross-sensitization was evaluated on PND 39 or PND 70 (adulthood). To this end, SAL- and MPD-pretreated groups received subcutaneous injections of SAL (1.0 mL/kg) or nicotine (0.4 mg/kg). All groups had 8 animals. Immediately after injections, locomotor activity was determined. The locomotor response to MPD challenge of MPD-pretreated rats was not significantly different from that of the SAL-pretreated group. Moreover, the locomotor response of MPD-pretreated rats to nicotine challenge was not significantly different from that of the SAL-pretreated group. This lack of sensitization and cross-sensitization suggests that MPD treatment during adolescence does not induce short- or long-term neuroadaptation in rats that could increase sensitivity to MPD or nicotine.

Involvement of dopamine receptors in diethylpropion-induced conditioning place preference

Diethylpropion (DEP) is an amphetamine-like agent used as an anorectic drug. Abuse of DEP has been reported and some restrictions of its use have been recently imposed. The conditioning place preference (CPP) paradigm was used to evaluate the reinforcing properties of DEP in adult male Wistar rats. After initial preferences were determined, animals weighing 250-300 g (N= 7 per group) were conditioned with DEP (10, 15 or 20 mg/kg). Only the dose of 15 mg/kg produced a significant place preference (358 + 39 vs 565 + 48s). Pretreatment with the D1 antagonist SCH 23390 (0.05 mg/kg, sc) 10 min before DEP (15 mg/kg, ip) blocked DEP-induced CPP (418 + 37 vs 389 + 31 s) while haloperidol (0.5 mg/kg, ip), a D2 antagonist, 15 min before DEP was ineffective in modifying place conditioning produced by DEP (385 + 36 vs 536 + 41 s). These results suggest that dopamine D1 receptors mediate the reinforcing effect of DEP.

Circadian time-dependent effects of fencamfamine on inhibition of dopamine uptake and release in rat striatal slices

Fencamfamine (FCF) is a central stimulant that facilitates central dopaminergic transmission through inhibition of dopamine uptake and enhanced release of the transmitter. We evaluated the changes in the inhibition of uptake and the release of striatal [3H]-dopamine at 9:00 and 21:00 h, times corresponding to maximal and minimal behavioral responses to FCF, respectively. Adult male Wistar rats (200-250 g) maintained on a 12-h light/12-h dark cycle (lights on at 7:00 h) were used. In the behavioral experiments the rats (N = 8 for each group) received FCF (3.5 mg/kg, ip) or saline at 9:00 or 21:00 h. Fifteen minutes after treatment the duration of activity (sniffing, rearing and locomotion) was recorded for 120 min. The basal motor activity was higher (28.6 + 4.2 vs 8.4 + 3.5 s) after saline administration at 21:00 h than at 9:00 h. FCF at a sigle dose significantly enhanced the basal motor activity (38.3 + 4.5 vs 8.4 + 3.5 s) and increased the duration of exploratory activity (38.3 + 4.5 vs 32.1 + 4.6 s) during the light, but not the dark phase. Two other groups of rats (N = 6 for each group) were decapitated at 9:00 and 21:00 h and striata were dissected for dopamine uptake and release assays. The inhibition of uptake and release of [3H]-dopamine were higher at 9:00 than at 21:00 h, suggesting that uptake inhibition and the release properties of FCF undergo daily variation. These data suggest that the circadian time-dependent effects of FCF might be related to a higher susceptibility of dopamine presynaptic terminals to the action of FCF during the light phase which corresponds to the rats' resting period.

The behavioral sensitization induced by fencamfamine is not related to plasma drug levels

Fencamfamine (FCF) is a CNS stimulant that facilitates central dopaminergic transmission primarily though blockade of dopamine uptake. In the present study we evaluated the relationship between plasma FCF concentration and behavioral sensitization effect. Adult male Wistar rats (250-300 g) received FCF (10 mg/Kg, ip) or saline oince or daily for 10 consecutive days (N = 10 for each group). Blood samples were collected 30 min after injections and plasma FCF was measured by gas chromatography using an electron capture detector. FCF treatment enhanced sniffing duration (16.8 ñ 0.8 vs 26.6 ñ 0.9s) and decreased rearing behavior (8.2 ñ 0.8 vs 3.7 ñ 0.6s) when days 1 and 10 of drug administration were compared. Comparison of pair of means by the Student t-test did not show significant differences in plasma FCF concentration (390 ñ 40 vs 420 ñ 11 ng/ml) when blood samples were collected 30 min after acute FCF administration or after daily administration of 10 mg/Kg for 10 days. In conclusion, the behavioral sensitization to FCF could not be correlated with plasma drug levels, and changes in the activity of dopaminergic systems should be considered to explain the sensitization to the effect of FCF

Daily variation in plasma concentration of fencamfamine and striatal dopamine receptors in rats

Fencamfamine (FCF) is a psychostimulant drug classified as an indirect dopamine agonist. In the present study we evaluated the daily variation in plasma FCF concentration and in striatal dopamine receptors. Adult male Wistar rats (250-300 g) maintained on a 12-h light/12-h dark cycle (lights on at 07:00 h) were used. Rats received FCF (10.0 mg/kg, ip) at 09:00, 15:00, 21:00 or 03:00 h and blood samples were collected 30 (N = 6) or 60 (N = 6) min after the injections. Plasma FCF was measured by gas chromatography using an electron capture detector. Two-way ANOVA showed significant differences in FCF concentration when blood samples were collected 30 min after the injection, and the highest value was obtained following injection at 21:00 h. Moreover, at 15:00, 21:00 and 03:00 h, plasma FCF levels were significantly lower 60 min after injection when compared to the 30-min interval. Two other groups of rats (N = 6) were decapitated at 09:00 or 21:00 h and the striata were dissected for the binding assays. The Bmax for [3H]-spiroperidol binding to striatal membranes was higher at 21:00 h, without changes in affinity constant (Kd). In conclusion, plasma FCF levels and dopamine receptors undergo daily variation, a phenomenon that should be considered to explain the circadian time-dependent effects of FCF

Effect of fencamfamine on avoidance performances of rats

The effects of fencamfamine (1.0 and 5.0 mg/kg, ip single dose) on an inhibitory task were studied in rats (N=15 per group).Post-training treatment with fencamfamine (1.0 mg/kg) significantly increased avoidance latency from 23 ñ 3 to 146 ñ 28 and 170 ñ 33 s for training day 1 and day 7, respectively, indicating an enhacement of retention.However, retention was significantly reduced with a high dose of fencamfamine (5.0 mg/kg). These results demonstrate that fencamfamine caused a reproducible dose-related increase and reduction in avoidance latency

Hyperprolactinemia induced by long-term domperidone treatment does not alter the sensitivity of strial dopamine receptors

We investigated the effect of hyperprolactinemia by long-term domperidone treatment (10.0 mg/kg, single daily dose, ip) on striatal dopamine (DA) receptor sensitivity in male Wistar rats weighing 250-300 g(N=8). Domperidone treatment for days continued to produce an increased in serum concentration of prolactin (PRL) form 17.3 ñ 2.2 to 33.1 ñ 7.3 and from 16.8 ñ 2.3 to 21.9 ñ 2.1, 2 and 72 h after domperidone withdrawal, respectively. Hyperprolactinemia induced by long-term domperidone treatment did not change binding sites (B max) and dissociation constant (Kd) of [3***H]-spiroperidol binding when compared to controls. These results show that byperprolactinemia induced by long-term domperidone treatment does not effect the sensitivity of striatal DA receptors presumably because the effect of neuroleptic drugs is due to their interaction with the receptors and not to the concomitant hyperprolactinemia

Striatal dopamine receptor supersensitivity afte long-term haloperiodol treatment of hypophysectomized rats

Dopamine (DA) receptor sensitivity was studied after long-term treatment with haloperidol (0.5 ad 3.0 mg/Kg, ip, single daily dose) or saline in hypophysectomized and infact rats. Haloperidol treatment for seven days produced a 25 to 125% increase in [3H]-spiroperidol binding to strial DA receptors in a dose-dependent fashion. The increase in binding sits (Bmax) was ximilar in both hypophysectomized and intact rats when compared to controls. The present results show that haloperidol treatment

On the mechanism which mediates the effects of long-term administration of fencamfamine in rats

This study analyzes the changes in the sensitivity of striatal dopaminergic (DA) receptors to apomorphine following withdrawal from long-term treatment with fencamfamine (10 mg/kg, for 40 days). Fencamfamine treatment decreased (34.8 + or - 3.2 vs 25.8 + or - 2.8,P<0.05) the stereotyped behavior induced by apomorfhine (2.0 mg/kg, sc), but potentiated the effect of apomorphine (0.02 mg/kg, sc) in reducing the striatal levels of homovanillic acid (HVA) (0.41 + or - 0.02 micron g/g vs 0.31 + or - 0.03 microng/g, P<0.01) and dihydroxyphenylacetic acid (DOPAC) (0.45 + or - 0.04 microng/g vs 0.34 + or - 0.03 microng/g, P<0.01). These results suggest that changes in pre- or postsynaptic DA receptors may underlie the tolerance and sensitization to the effects of fencamfamine

uso de psicoestimulantes e energizantes por universitarios. / Use of psychostimulants and energizing drugs by university students

Foi aplicado um questionario sobre a incidencia de uso de alguns medicamentos psicotropicos, com enfase em psicoestimulantes e energizantes, em uma amostra de estudantes da area bimedica da Universidade de Sao Paulo. Dos medicamentos selecionados, as incidencias mais elevadas foram com Reactivan, Hipofagin, Nootropil e glicose. Dos grupos de medicamentos, os tranquilizantes e psicoestimulantes apresentaram alta incidencia de uso. A automedicacao e o consumo de medicamentos controlados sem prescricao foram caracteristicas do uso das drogas selecionadas

Padroes de custo e prescricoes em psicofarmacoterapia. / Patterns of cost and prescriptions in psychochemotherapy

Foram selecionados os nomes quimicos e comerciais dos ansioliticos, hipnoticos-sedativos, antidepressivos e neurolepticos e suas associacoes disponiveis no mercado farmaceutico do Pais. Foram atualizados os custos de cada tratamento para diversas drogas e analisadas as variacoes dos padroes de custos e prescricao ocorridas num periodo de 5 anos. Os ansioliticos e suas associacoes foram os psicofarmacos mais vendidos em 1982. Continuam a existir diferenca de custo no tratamento mensal das drogas, principalmente porque um mesmo sal (e.g. diazepam) e comercializado com varios nomes de fantasia e com precos bastante variaveis entre eles. As drogas mais rentaveis foram as mais vendidas e prescritas, independentemente de sua eficacia clinica em relacao as demais