1,721,014 research outputs found
Energy drinks at adolescence: Awareness or unawareness?
No full textEnergy drinks (EDs) are beverages similar to soft drinks, characterized by high
caffeine concentrations with additional ingredients like taurine and vitamins,
marketed for boosting energy, reducing tiredness, increasing concentration, and
for their ergogenic effect. The majority of consumers are children, adolescents,
and young athletes. Although EDs companies claim about the ergogenic and
remineralizing properties of their products, there is a serious lack of evidence
at preclinical as well as clinical level to validate their benefits. The regular
intake and long-term consequences of these caffeinated drinks are not well
documented, especially the possible negative effects in adolescents whose brain
is still developing. EDs combined with alcohol are also gaining popularity among
adolescents and different publications indicate that this combined consumption
might increase the risk to develop an alcohol use disorder, as well as produce
serious adverse cardiovascular effects. There is an increasing need to disseminate
knowledge on EDs damage on health, so that adolescents can be aware about
the potential harmful outcomes of consuming these drink
Reciprocal changes in dopamine responsiveness in the nucleus accumbens shell and core and in the dorsal caudate-putamen in rats sensitized to morphine
No full textIn this study, we describe a model of opiate sensitization characterized by a brief schedule of treatment with repeated morphine administrations. In this model, we investigated the changes produced by repealed morphine treatment on dopamine transmission at the level of the two major terminal dopaminergic areas, the dorsolateral caudate-putamen and the nucleus accumbens in its two subdivisions, the shell and the core. Rats were treated twice a day for three days with increasing doses of morphine (10, 20 and 40 mg/kg, s.c.) or with saline. After 15 days of withdrawal, rats were challenged with 1 and 5 mg/kg (s.c.) of morphine, and dopamine transmission was monitored by microdialysis. In this model, we show that repeated morphine produces a strong behavioral sensitization accompained by increased stimulation of dopamine transmission in the core of the nucleus accumbens and in the caudate-putamen, and by a decreased stimulation of dopamine transmission in the shell of the nucleus accumbens, as compared to control rats. Moreover, we administered to these animals amphetamine (0.5 mg/kg, s.c.) and cocaine (10 mg/kg, i.p.) to assess whether cross-sensitization occurs between opiates and psychostimulants in conditions independent of the context. In the present study, we did not observe either behavioral or biochemical sensitization to amphetamine and to cocaine in rats sensitized to morphine.
These results suggest that rats behaviorally sensitized to morphine show opposite changes in the stimulant effect of morphine in the nucleus accumbens shell and core and in the dorsal caudate-putamen, Moreover, this study suggests that sensitization of the dopamine system to a given agent does not necessarily extend to drugs of abuse of different pharmacological classes
Differences in dopamine responsiveness to drugs of abuse in the nucleus accumbens shell and core of Lewis and Fischer 344 rats
No full textThe use of inbred rat strains provides a tool to investigate the role of genetic factors in drug abuse. Two such strains are Lewis and Fischer 344 rats. Although several biochemical and hormonal differences have been observed between Lewis and Fischer 344 strains, a systematic comparison of the effect of different drugs of abuse on dopamine (DA) transmission in the shell and core of the nucleus accumbens of these strains is lacking. We therefore investigated, by means of dual probe microdialysis, the effect of different doses of morphine (1.0, 2.5, and 5.0 mg/kg), amphetamine (0.25, 0.5, and 1.0 mg/kg) and cocaine (5, 10, and 20 mg/kg) on DA transmission in the shell and in the core of nucleus accumbens. Behavior was monitored during microdialysis. In general, Lewis rats showed greater DA responsiveness in the NAc core compared to F344 rats except after 2.5 mg/kg of morphine and 20 mg/kg of cocaine. In the NAc shell, different effects were obtained depending on drug and dose: after 1.0 mg/kg of morphine no strain differences were observed, at 2.5 and 5.0 mg/kg Lewis rats showed greater increase in DA in the NAc shell. Following amphetamine and cocaine challenge, Lewis rats showed greater DA increase in the shell after 0.25 mg/kg of amphetamine and 20 mg/kg of cocaine. Behavioral activation was greater in Lewis rats in response to the lowest dose of morphine (1.0 mg/kg), to the highest dose of amphetamine (1.0 mg/kg) and to all doses of cocaine. These differences might be the basis for the different behavioral responses of these strains to drugs of abuse
Adolescent Cannabis exposure differentially affects Heroin Reinforcement and Accumbens Dopamine transmission in Lewis and Fisher344 rats
No full textBackground: Vulnerability to drug addiction depends on acquired as well as genetic factors (Swendsen & Le Moal 2010). Among acquired factors is previous exposure to other drugs of abuse. Thus, exposure to Cannabis has been suggested to predispose to heroin abuse and dependence (Gateway Hypothesis) (Kandel et al. 2006). Here we studied the influence of adolescent delta 9-THC exposure on heroin reward and renforcement and on the in vivo dopamine stimulant properties of heroin in two inbred rat strains differentially vulnerable to drugs of abuse, the addiction prone Lewis and the addiction resistant Fisher344 strain.
Results: THC increased extracellular DA, as estimated by microdialysis, in Lewis but not in Fischer 344 rats. Adolescent THC exposure potentiated DA stimulant effects of heroin in the shell and core of Lewis and only in the core of Fischer344 rats. Control Lewis rats developed stronger conditioned place preference (CPP) to heroin and resistance to extinction compared with Fischer344 strain. In Lewis rats, THC exposure did not increse heroin CPP but potentiated the effect of heroin priming. In Fischer344 rats, THC exposure increased heroin CPP and made it resistant to extinction. Lewis rats showed marked seeking reactions during extinction and hedonic reactions in response to heroin priming. THC pre-exposure increased responding for iv heroin self-administration on FR3 and FR5 and on progressive ratio 3-4 in Lewis but not in Fisher344 rats. After extinction, presentation of discriminative stimuli associated to drug availability on the active nose-poke as well as priming by passive heroin exposure, reinstated responding more effectively in Lewis rats pre-exposed to THC than in saline controls.
Conclusions: These observations suggest that, in genetically predisposed individuals, adolescent Cannabis exposure can increase vulnerability to heroin addiction by augmenting heroin reinforcing properties.
These studies were founded by the Dipartimento politiche antidroga, Presidenza del Consiglio, Ital
Genotype dependent adaptive changes in mesolimbic dopamine transmission after adolescent nicotine exposure: possible underlying mechanisms in the gateway effect of nicotine
No full textNicotine differentially affects dopamine transmission in the nucleus accumbens shell and core of Lewis and Fischer 344 rats
No full textGenetic factors are known to affect the reinforcing properties of nicotine. Thus, inbred Lewis rats have been reported to be more sensitive to nicotine compared to Fischer 344 rats in self-administration, conditioned place preference and drug discrimination paradigms. In order to clarify the mechanisms of these differences we investigated, by means of dual probe microdialysis, the effect of different doses of nicotine (0.05, 0.1, 0.2, 0.4 mg/kg s.c.) on dopamine transmission in the shell and in the core of nucleus accumbens. Behavior was monitored during microdialysis. While no differences were observed between strains in dopamine basal values, Lewis rats, compared to Fischer 344 ones, showed in general a larger increase of DA transmission following nicotine both in the shell and in the core of the nucleus accumbens. In regard to behavioral stimulation no differences were observed between strains at higher doses while at the lowest doses Lewis rats appeared more sensitive than Fischer 344 rats to the locomotor stimulating effects of nicotine. These results suggest that strain-related differences in the sensitivity of mesolimbic dopamine transmission to nicotine might be involved in the reported differences in the reinforcing effect of nicotine in Lewis and Fischer 344 rats
Differential changes in accumbens shell and core dopamine in behavioral sensitization to nicotine
No full textRepeated treatment with nicotine has been shown to sensitize rats to its locomotor stimulant effects and to its properties to stimulate mesolimbic dopamine transmission. We investigated the relationship between sensitization of nicotine induced locomotor stimulation and activation of dopamine transmission in the nucleus accumbens shell and core. Rats were administered daily for 5 days with 0.4 mg/kg s.c. of nicotine or with saline and 24 h later, dopamine was monitored by microdialysis in the shell and in the core of nucleus accumbens and behavioral activity was scored after challenge with nicotine (0. 4 mg/kg s.c.). Behavioral sensitization to nicotine was associated with a reduced response of dopamine transmission in the shell and with an increased one in the core of nucleus accumbens
Conditioned saccharin avoidance and sensitization to drugs of abuse
No full textSaccharin avoidance conditioned by drugs of abuse (CSA) has been interpreted as an expression of the appetitive, dopamine-dependent, properties of the drug. Repeated exposure to these drugs induces an increase (sensitization) of their motor stimulant properties associated with differential changes in DA transmission in the NAc shell and core. The present study investigated the changes in drug CSA induced by schedules of repeated drug exposure that induce behavioral sensitization. CSA was performed in a two-bottle choice paradigm with two saccharin-drug associations in rats previously sensitized to morphine, cocaine, amphetamine and nicotine. In control rats morphine (1 and 5 mg/kg s.c.), cocaine (5 and 10 mg/kg i.p.), amphetamine (0.25 and 0.5 mg/kg s.c.) and nicotine (0.4 mg/kg s.c.) induced dose-dependent CSA. Sensitization to morphine, cocaine and nicotine, which is known to reduce the responsiveness of NAc shell DA to the same drugs, also reduced CSA. In contrast, sensitization to amphetamine, that does not affect the responsiveness of NAc shell DA to the drug, failed to affect CSA. The results are consistent with the hypothesis that NAc shell DA is a substrate of the appetitive properties of drugs of abus
Calcium-dependent, tetrodotoxin-sensitive stimulation of cortical serotonin release after a tryptophan load.
No full textThe effect of intraperitoneal administration of tryptophan (50, 100, or 200 mg/kg) on extracellular concentrations of tryptophan, serotonin (5-hydroxytryptamine, 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) was studied in the cortex of freely moving rats by transcerebral dialysis. Rats were implanted with dialysis probes in the frontal cortex, and experiments were performed 24 h later. Tryptophan, 5-HT, and 5-HIAA were quantified in 20-min samples of dialysate by HPLC with electrochemical detection after separation on reverse-phase columns. Tryptophan administration resulted in a significant increase of tryptophan, 5-HT, and 5-HIAA levels in dialysates. The maximal increase of 5-HT and 5-HIAA output was approximately 150% over basal values. Perfusion with Ringer's solution containing tetrodotoxin (1 microM) reduced 5-HT output by 90% and prevented the increase of 5-HT and 5-HIAA content after 100 mg/kg of tryptophan. Similar results were obtained after perfusion with Ringer's solution without Ca2+. The results indicate that a tryptophan load stimulates the physiological release of 5-HT
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