Caffeine and a selective adenosine A2A receptor antagonist induce sensitization and cross-sensitization behavior associated with increased striatal dopamine in mice

Using caffeine as a chemical means to induce flow states

Flow is an intrinsically rewarding state characterised by positive affect and total task absorption. Because cognitive and physical performance are optimal in flow, chemical means to facilitate this state are appealing. Caffeine, a non-selective adenosine receptor antagonist, has been emphasized as a potential flow-inducer. Thus, we review the psychological and biological effects of caffeine that, conceptually, enhance flow. Caffeine may facilitate flow through various effects, including: i) upregulation of dopamine D1/D2 receptor affinity in reward-associated brain areas, leading to greater energetic arousal and 'wanting'; ii) protection of dopaminergic neurons; iii) increases in norepinephrine release and alertness, which offset sleep-deprivation and hypoarousal; iv) heightening of parasympathetic high frequency heart rate variability, resulting in improved cortical stress appraisal, v) modification of striatal endocannabinoid-CB1 receptor-signalling, leading to enhanced stress tolerance; and vi) changes in brain network activity in favour of executive function and flow. We also discuss the application of caffeine to treat attention deficit hyperactivity disorder and caveats. We hope to inspire studies assessing the use of caffeine to induce flow.

The GLT-1 enhancer clavulanic acid suppresses cocaine place preference behavior and reduces GCPII activity and protein levels in the rat nucleus accumbens

The β-lactam antibiotic ceftriaxone (CTX) is a glutamate transporter subtype 1 (GLT-1) enhancer that reduces cocaine reinforcing efficacy and relapse in rats, but pharmacokinetic liabilities limit translational utility. An attractive alternative is clavulanic acid (CLAV), a structurally related β-lactamase inhibitor and component of FDA-approved Augmentin. CLAV retains the GLT-1 enhancing effects of CTX but displays greater oral bioavailability, brain penetrability and negligible antibacterial activity. CLAV reduces morphine conditioned place preference (CPP) and ethanol consumption in rats, but knowledge about the efficacy of CLAV in preclinical models of drug addiction remains sparse. Here, we investigated effects of CLAV (10 mg/kg, IP) on the acquisition, expression, and maintenance of cocaine CPP in rats, and on two glutamate biomarkers associated with cocaine dependence, GLT-1 and glutamate carboxypeptidase II (GCPII). CLAV administered during cocaine conditioning (10 mg/kg, IP x 4 d) did not affect the development of cocaine CPP. However, a single CLAV injection, administered after the conditioning phase, reduced the expression of cocaine CPP. In rats with established cocaine preference, repeated CLAV administration facilitated extinction of cocaine CPP. In the nucleus accumbens, acute CLAV exposure reduced GCPII protein levels and activity, and a 10-d CLAV treatment regimen enhanced GLT-1 levels. These results suggest that CLAV reduces expression and maintenance of cocaine CPP but lacks effect against development of CPP. Moreover, the ability of a single injection of CLAV to reduce both GCPII activity and protein levels, as well as expression of cocaine CPP, points toward studying GCPII as a therapeutic target of CLAV.

Physical Activity and Music to Counteract Mental Fatigue

Mental fatigue impairs both cognitive and physical performance. Bioactive substances (e.g., caffeine) have been used to counteract mental fatigue but could have side effects. The present study aimed to test two non-bioactive strategies to counteract mental fatigue: physical activity and listening to music. The participants first performed an arm-pointing task, then carried out a 32-min cognitively demanding task to induce mental fatigue (TLDB task), followed by another arm-pointing task at the end of the experiment. Between the end of the cognitively demanding task and the last arm-pointing task, 20 min went during which participants performed either 15 min of physical activity, of listening to music or of discussion (control). The subjective feeling of mental fatigue was assessed before each arm-pointing task and after the cognitively demanding task. For "physical activity" and "listening to music" groups, EEG was recorded at rest after each evaluation of subjective feeling of mental fatigue and during the cognitively demanding task. An increase in alpha power during the cognitively demanding task evidenced the presence of mental fatigue, without recovery during the following 20-min period. In the control condition, the arm-pointing task performance was deteriorated 20-min after the cognitively demanding task, while it remained stable after both physical activity and listening to music. Furthermore, recovery on the subjective feeling of mental fatigue was similar for both groups. The present results suggested that practicing physical activity and listening to music could be efficient strategies to counteract the negative effects of mental fatigue on motor performances.

Targeting Dopamine D2, Adenosine A2A, and Glutamate mGlu5 Receptors to Reduce Repetitive Behaviors in Deer Mice

Repetitive behaviors are seemingly purposeless patterns of behavior that vary little in form and are characteristic of many neurodevelopmental, psychiatric, and neurologic disorders. Our work has identified an association between hypofunctioning of the indirect basal ganglia pathway and the expression of repetitive behavior in the deer mouse model. In this study, we targeted indirect pathway cells of the striatum with single drugs and drug combinations that bind to dopamine D₂, adenosine A_2A, and glutamate mGlu₅ receptors. These receptors function both individually and as receptor heteromers. We found that only the triple drug cocktail (L-741,626+CGS21680+CDPPB) that was designed to increase striatal indirect basal ganglia pathway cell function reduced repetitive behavior in adult male deer mice. No single drug or double drug combinations were effective at selectively reducing repetitive behavior. We found this triple drug cocktail reduced repetitive behavior in both short-acting and long-acting formulations and was effective throughout 7 days of daily administration. Conversely, another triple drug cocktail (quinpirole+SCH58261+MTEP) that was designed to further reduce striatal indirect basal ganglia pathway cell function caused a significant increase in repetitive behavior. Significant and behaviorally selective effects on repetitive behavior were only achieved with the triple drug cocktails that included doses of L-741,626 and quinpirole that have off-target effects (e.g., dopamine D₃ receptors). These data further a role for decreased indirect basal ganglia pathway activation in repetitive behavior and suggest that targeting these receptors and/or heteromeric complexes on the indirect pathway neurons of the striatum may offer pharmacotherapeutic benefit for individuals with repetitive behavior disorders.

Chronic adenosine A2A receptor blockade induces locomotor sensitization and potentiates striatal LTD IN GPR37-deficient mice

Adenosine A_2A receptors (A_2A R) play a key role in modulating dopamine-dependent locomotor activity, as heralded by the sensitization of locomotor activity upon chronic A_2A R blockade, which is associated with elevated dopamine levels and altered corticostriatal synaptic plasticity. Since the orphan receptor GPR37 has been shown to modulate A_2A R function in vivo, we aimed to test whether the A_2A R-mediated sensitization of locomotor activity is GPR37-dependent and involves adaptations of synaptic plasticity. To this end, we administered a selective A_2A R antagonist, SCH58261 (1 mg/kg, i.p.), daily for 14 days, and the locomotor sensitization, striatum-dependent cued learning, and corticostriatal synaptic plasticity (i.e., long-term depression) were compared in wild-type and GPR37^-/- mice. Notably, GPR37 deletion promoted A_2A R-associated locomotor sensitization but not striatum-dependent cued learning revealed upon chronic SCH58261 treatment of mice. Furthermore, chronic A_2A R blockade potentiated striatal long-term depression in corticostriatal synapses of GPR37^-/- but not of wild-type mice, thus correlating well with neurochemical alterations of the adenosinergic system. Overall, these results revealed the importance of GPR37 regulating A_2A R-dependent locomotor sensitization and synaptic plasticity in the basal ganglia circuitry. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Open Science: This manuscript was awarded with the Open Materials Badge. For more information see: https://cos.io/our-services/open-science-badges/.

Investigating the possible mechanisms involved in adenosine preconditioning-induced cardioprotection in rats

BACKGROUND

Adenosine is a breakdown product of adenosine triphosphate and plays an important role in pharmacological preconditioning. The cardioprotective effects of adenosine preconditioning are well established. However, the possible mechanisms need to be explored.

AIM

This study was aimed to investigate the possible mechanisms involved in adenosine preconditioning-induced cardioprotection in rats.

METHODS

Rat heart was isolated and perfused on Langendorff apparatus. Global ischemia for 30 minutes followed by reperfusion for 120 minutes was employed to produce myocardial injury. Myocardial injury was assessed by measuring myocardial infarct size, release of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and hemodynamic parameters including left ventricular developed pressure (LVDP), dp/dt_max, and dp/dt_min . Serum nitrite levels were measured as an index of nitric oxide release in blood.

RESULTS

Adenosine (4 mg/kg) preconditioning significantly decreased ischemia-reperfusion-induced increase in LDH, CK release, infarct size, improved LVDP, dp/dt_max and dp/dt_min, and increased serum nitrite levels. Pretreatment with L-NAME, a specific NOS inhibitor, (5 mg/kg) and montelukast, leukotriene receptor antagonist, (10 mg/kg) significantly abrogated the cardioprotective effect of adenosine preconditioning. However, seratrodast, thromboxane A₂ antagonist, (15 mg/kg) had no effect on adenosine-induced cardioprotection. Sodium nitroprusside (SNP) preconditioning also produced cardioprotective effects. However, caffeine (20 mg/kg) (adenosine receptor blocker) and seratrodast (15 mg/kg) had no effect on SNP-induced cardioprotection. Administration of montelukast abrogated the cardioprotective effects of SNP preconditioning-induced cardioprotection.

CONCLUSION

Adenosine preconditioning may increase the release of nitric oxide, which in turn may increase the release of cysteinyl leukotrienes to confer cardioprotection.

Adenosine A2A receptor and ERK-driven impulsivity potentiates hippocampal neuroblast proliferation

Dampened adenosine A_2A receptor (A_2AR) function has been implicated in addiction through enhancement of goal-directed behaviors. However, the contribution of the A_2AR to the control of impulsive reward seeking remains unknown. Using mice that were exposed to differential reward of low rate (DRL) schedules during Pavlovian-conditioning, second-order schedule discrimination, and the 5-choice serial reaction time task (5-CSRTT), we demonstrate that deficits of A_2AR function promote impulsive responses. Antagonism of the A_2AR lowered ERK1 and ERK2 phosphorylation in the dorsal hippocampus (dHip) and potentiated impulsivity during Pavlovian-conditioning and the 5-CSRTT. Remarkably, inhibition of ERK1 and ERK2 phosphorylation by U0126 in the dHip prior to Pavlovian-conditioning exacerbated impulsive reward seeking. Moreover, we found decreased A_2AR expression, and reduced ERK1 and ERK2 phosphorylation in the dHip of equilibrative nucleoside transporter type 1 (ENT1^-/-) null mice, which displayed exacerbated impulsivity. To determine whether impulsive response behavior is associated with hippocampal neuroblast development, we investigated expression of BrdU⁺ and doublecortin (DCX⁺) following 5-CSRTT testing. These studies revealed that impulsive behavior driven by inhibition of the A_2AR is accompanied by increased neuroblast proliferation in the hippocampus.

Neuroprotective and Therapeutic Effect of Caffeine on the Rat Model of Parkinson's Disease Induced by Rotenone

The present study aimed to investigate the protective and therapeutic effects of caffeine on rotenone-induced rat model of Parkinson's disease (PD). Rats were divided into control, PD model induced by rotenone (1.5 mg/kg intraperitoneally (i.p.) for 45 days), protected group injected with caffeine (30 mg/kg, i.p.) and rotenone for 45 days (during the development of PD model), and treated group injected with caffeine (30 mg/kg, i.p.) for 45 days after induction of PD model. The data revealed a state of oxidative and nitrosative stress in the midbrain and the striatum of animal model of PD as indicated from the increased lipid peroxidation and nitric oxide levels and the decreased reduced glutathione level and activities of glutathione-S-transferase and superoxide dismutase. Rotenone induced a decrease in acetylcholinesterase and Na⁺/K⁺-ATPase activities and an increase in tumor necrosis factor-α level in the midbrain and the striatum. Protection and treatment with caffeine ameliorated the oxidative stress and the changes in acetylcholinesterase and Na⁺/K⁺-ATPase activities induced by rotenone in the midbrain and the striatum. This was associated with improvement in the histopathological changes induced in the two areas of PD model. Caffeine protection and treatment restored the depletion of midbrain and striatal dopamine induced by rotenone and prevented decline in motor activities (assessed by open field test) and muscular strength (assessed by traction and hanging tests) and improved norepinephrine level in the two areas. The present study showed that caffeine offered a significant neuroprotection and treatment against neurochemical, histopathological, and behavioral changes in a rotenone-induced rat model of PD.

Potential Role of Caffeine in the Treatment of Parkinson's Disease

Parkinson’s disease [PD] is the second most common neurodegenerative disorder after Alzheimer’s disease, affecting 1% of the population over the age of 55. The underlying neuropathology seen in PD is characterised by progressive loss of dopaminergic neurons in the substantia nigra pars compacta with the presence of Lewy bodies. The Lewy bodies are composed of aggregates of α-synuclein. The motor manifestations of PD include a resting tremor, bradykinesia, and muscle rigidity. Currently there is no cure for PD and motor symptoms are treated with a number of drugs including levodopa [L-dopa]. These drugs do not delay progression of the disease and often provide only temporary relief. Their use is often accompanied by severe adverse effects. Emerging evidence from both in vivo and in vitro studies suggests that caffeine may reduce parkinsonian motor symptoms by antagonising the adenosine A_2A receptor, which is predominately expressed in the basal ganglia. It is hypothesised that caffeine may increase the excitatory activity in local areas by inhibiting the astrocytic inflammatory processes but evidence remains inconclusive. In addition, the co-administration of caffeine with currently available PD drugs helps to reduce drug tolerance, suggesting that caffeine may be used as an adjuvant in treating PD. In conclusion, caffeine may have a wide range of therapeutic effects which are yet to be explored, and therefore warrants further investigation in randomized clinical trials.

Mechanisms of the psychostimulant effects of caffeine: implications for substance use disorders

BACKGROUND

The psychostimulant properties of caffeine are reviewed and compared with those of prototypical psychostimulants able to cause substance use disorders (SUD). Caffeine produces psychomotor-activating, reinforcing, and arousing effects, which depend on its ability to disinhibit the brake that endogenous adenosine imposes on the ascending dopamine and arousal systems.

OBJECTIVES

A model that considers the striatal adenosine A2A-dopamine D2 receptor heteromer as a key modulator of dopamine-dependent striatal functions (reward-oriented behavior and learning of stimulus-reward and reward-response associations) is introduced, which should explain most of the psychomotor and reinforcing effects of caffeine.

HIGHLIGHTS

The model can explain the caffeine-induced rotational behavior in rats with unilateral striatal dopamine denervation and the ability of caffeine to reverse the adipsic-aphagic syndrome in dopamine-deficient rodents. The model can also explain the weaker reinforcing effects and low abuse liability of caffeine, compared with prototypical psychostimulants. Finally, the model can explain the actual major societal dangers of caffeine: the ability of caffeine to potentiate the addictive and toxic effects of drugs of abuse, with the particularly alarming associations of caffeine (as adulterant) with cocaine, amphetamine derivatives, synthetic cathinones, and energy drinks with alcohol, and the higher sensitivity of children and adolescents to the psychostimulant effects of caffeine and its potential to increase vulnerability to SUD.

CONCLUSIONS

The striatal A2A-D2 receptor heteromer constitutes an unequivocal main pharmacological target of caffeine and provides the main mechanisms by which caffeine potentiates the acute and long-term effects of prototypical psychostimulants.

Effects of caffeine intake and smoking on neurocognition in schizophrenia

Although most studies support the beneficial effects of caffeine on neurocognition, its effects have never been assessed in psychiatric patients. In addition, results from studies in smokers are contradictory. Moreover, there are no data available about the neurocognitive effects of caffeine and tobacco together. We explored the concomitant effects of regular caffeine and tobacco intake on neurocognition in 52 schizophrenic patients and 61 healthy controls. Verbal fluency, processing speed, and working, visual and verbal memory were assessed. For each measurement, two tasks with two levels of complexity were administered. Our results showed that caffeine intake had beneficial effects on male schizophrenic patients only in complex tasks requiring deeper cognitive processing (semantic fluency, cognitive speed, working memory, and visual memory). Female patients and controls were unaffected. In contrast, smoking had a negative effect on male, but not on female, schizophrenic patients in semantic fluency. The effects of smoking in controls were inconsistent. In conclusion, our data showed, for the first time, beneficial effects of caffeine intake on neurocognition in male schizophrenic patients. These data suggest that further research of therapeutics based on caffeine is needed, as this could be beneficial for schizophrenic patients. In contrast, smoking appears to be detrimental.

Purinergic receptors in psychiatric disorders

Psychiatric disorders describe different mental or behavioral patterns, causing suffering or poor coping of ordinary life with manifold presentations. Multifactorial processes can contribute to their development and progression. Purinergic neurotransmission and neuromodulation in the brain have attracted increasing therapeutic interest in the field of psychiatry. Purine nucleotides and nucleosides are well recognized as signaling molecules mediating cell to cell communication. The actions of ATP are mediated by ionotropic P2X and metabotropic P2Y receptor subfamilies, whilst the actions of adenosine are mediated by P1 (A1 or A2) adenosine receptors. Purinergic mechanisms and specific receptor subtypes have been shown to be linked to the regulation of many aspects of behavior and mood and to dysregulation in pathological processes of brain function. In this review the recent knowledge on the role of purinergic receptors in the two most frequent psychiatric diseases, major depression and schizophrenia, as well as on related animal models is summarized. At present the most promising data for therapeutic strategies derive from investigations of the adenosine system emphasizing a unique function of A2A receptors at neurons and astrocytes in these disorders. Among the P2 receptor family, in particular P2X7 and P2Y1 receptors were related to disturbances in major depression and schizophrenia, respectively. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Sensitization and Tolerance Following Repeated Exposure to Caffeine and Alcohol in Mice

BACKGROUND

Energy drinks are popular mixers with alcohol. While energy drinks contain many ingredients, caffeine is an important pharmacologically active component and is generally present in larger amounts than in other caffeinated beverages. In these studies, we investigated the hypothesis that caffeine would influence the effects of alcohol (ethanol [EtOH]) on conditioned taste aversion (CTA), ataxia, and locomotor activity (LA) after repeated exposure.

METHODS

Four groups of mice were exposed by oral gavage twice daily to vehicle, EtOH (4 g/kg), caffeine (15 mg/kg), or the EtOH/caffeine combination. CTA to saccharin and ataxia in the parallel rod task was evaluated after 8 or 16 gavages, respectively, using EtOH (1 to 3 g/kg) or EtOH/caffeine (3 mg/kg + 2 g/kg) challenges. In addition, LA was evaluated initially and after repeated exposure to oral gavage of these drugs and doses.

RESULTS

Repeated oral gavage of EtOH produced significant locomotor sensitization, with those mice increasing total distance traveled by 2-fold. The locomotor response to caffeine, while significantly greater than vehicle gavage, did not change with repeated exposure. On the other hand, repeated gavage of caffeine/EtOH combination produced a substantial increase in total distance traveled after repeated exposure (~4-fold increase). After repeated EtOH exposure, there was significant tolerance to EtOH in the CTA and parallel rod tests. However, neither a history of caffeine exposure nor including caffeine influenced EtOH-induced CTA. Interestingly, a history of caffeine exposure increased the ataxic response to the caffeine/EtOH combination and appeared to reduce the ataxic response to high doses of EtOH.

CONCLUSIONS

The data support the general hypothesis that repeated exposure to caffeine influences the response to EtOH. Together with previously published work, these data indicate that caffeine influences some EtOH-related behaviors, notably locomotion and ataxia, but appears not to influence the expression of conditioned behaviors.

The Janus face of caffeine

Caffeine is certainly the psychostimulant substance most consumed worldwide. Over the past years, chronic consumption of caffeine has been associated with prevention of cognitive decline associated to aging and mnemonic deficits of brain disorders. While its preventive effects have been reported extensively, the cognitive enhancer properties of caffeine are relatively under debate. Surprisingly, there are scarce detailed ontogenetic studies focusing on neurochemical parameters related to the effects of caffeine during prenatal and earlier postnatal periods. Furthermore, despite the large number of epidemiological studies, it remains unclear how safe is caffeine consumption during pregnancy and brain development. Thus, the purpose of this article is to review what is currently known about the actions of caffeine intake on neurobehavioral and adenosinergic system during brain development. We also reviewed other neurochemical systems affected by caffeine, but not only during brain development. Besides, some recent epidemiological studies were also outlined with the control of "pregnancy signal" as confounding variable. The idea is to tease out how studies on the impact of caffeine consumption during brain development deserve more attention and further investigation.

A role for dopamine-mediated learning in the pathophysiology and treatment of Parkinson's disease

Dopamine contributes to corticostriatal plasticity and motor learning. Dopamine denervation profoundly alters motor performance, as in Parkinson's disease (PD); however, the extent to which these symptoms reflect impaired motor learning is unknown. Here, we demonstrate a D2 receptor blockade-induced aberrant learning that impedes future motor performance when dopamine signaling is restored, an effect diminished by coadministration of adenosine antagonists during blockade. We hypothesize that an inappropriate corticostriatal potentiation in striatopallidal cells of the indirect pathway underlies aberrant learning. We demonstrate synaptic potentiation in striatopallidal neurons induced by D2 blockade and diminished by application of an adenosine antagonist, consistent with behavioral observations. A neurocomputational model of the basal ganglia recapitulates the behavioral pattern and further links aberrant learning to plasticity in the indirect pathway. Thus, D2-mediated aberrant learning may contribute to motor deficits in PD, suggesting new avenues for the development of therapeutics.

Interactions of intergenic microRNAs with mRNAs of genes involved in carcinogenesis

miRNAs regulate gene expression by binding with mRNAs of many genes. Studying their effects on genes involved in oncogenesis is important in cancer diagnostics and therapeutics. The RNAHybrid 2.1 program was used to predict the strong miRNA binding sites (p < 0.0005) in target mRNAs. The program Finder 2.2 was created to verify 784 intergenic miRNAs (ig-miRNA) origin. Among 54 considered oncogenes and tumor suppressor genes, 47 genes are the best targets for ig-miRNAs. Accordingly, these genes are strongly regulated by 111 ig-miRNAs. Some miRNAs bind several mRNAs, and some mRNAs have several binding sites for miRNAs. Of the 54 mRNAs, 21.8%, 43.0%, and 35.2% of the miRNA binding sites are present in the 5'UTRs, CDSes, and 3'UTRs, respectively. The average density of the binding sites for miRNAs in the 5'UTR was 4.4 times and 4.1 times greater than in the CDS and the 3'UTR, respectively. Three types of interactions between miRNAs and mRNAs were identified, which differ according to the region of the miRNA bound to the mRNA: 1) binding occurs predominantly via the 3'-region of the miRNA; 2) binding occurs predominantly through the central region of the miRNA; and 3) binding occurs predominantly via the 5'-region of the miRNA. Several miRNAs effectively regulate only one gene, and this information could be useful in molecular medicine to modulate translation of the target mRNA. We recommend described new sites for validation by experimental investigation.

The impact of commercially available purinergic ligands on purinergic signalling research

Due to the extremely wide-spread expression of purinergic receptors, purinergic signalling has been implicated in numerous physiological and pathophysiological areas. To better understand the involvement of purinergic receptors in such areas, the researcher's requirement for diverse and varied purinergic receptor ligands has greatly increased. This has generated increased commercial opportunities for life science suppliers, and ultimately, has led to a rapid expansion in the number of commercially available purinergic receptor ligands. The wide-spread availability of ligands to researchers has greatly benefited the scientific community, nurturing the rapid and continued expansion of the purinergic signalling field.

Purinergic signalling: from normal behaviour to pathological brain function

Purinergic neurotransmission, involving release of ATP as an efferent neurotransmitter was first proposed in 1972. Later, ATP was recognised as a cotransmitter in peripheral nerves and more recently as a cotransmitter with glutamate, noradrenaline, GABA, acetylcholine and dopamine in the CNS. Both ATP, together with some of its enzymatic breakdown products (ADP and adenosine) and uracil nucleotides are now recognised to act via P2X ion channels and P1 and P2Y G protein-coupled receptors, which are widely expressed in the brain. They mediate both fast signalling in neurotransmission and neuromodulation and long-term (trophic) signalling in cell proliferation, differentiation and death. Purinergic signalling is prominent in neurone-glial cell interactions. In this review we discuss first the evidence implicating purinergic signalling in normal behaviour, including learning and memory, sleep and arousal, locomotor activity and exploration, feeding behaviour and mood and motivation. Then we turn to the involvement of P1 and P2 receptors in pathological brain function; firstly in trauma, ischemia and stroke, then in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's, as well as multiple sclerosis and amyotrophic lateral sclerosis. Finally, the role of purinergic signalling in neuropsychiatric diseases (including schizophrenia), epilepsy, migraine, cognitive impairment and neuropathic pain will be considered.

Ceftriaxone prevents the induction of cocaine sensitization and produces enduring attenuation of cue- and cocaine-primed reinstatement of cocaine-seeking

Ceftriaxone is a beta-lactam antibiotic which has been found to increase the expression and function of the major glutamate transporter, GLT-1. It has previously been shown that GLT-1 expression is decreased in the nucleus accumbens following cocaine self-administration and extinction training; ceftriaxone given in the days immediately prior to reinstatement testing attenuates both cue- and cocaine-primed reinstatement. Here we tested the ability of ceftriaxone pre-treatment (for 5 days prior to the first cocaine exposure) to prevent the induction of cocaine sensitization and the acquisition of cocaine self-administration. We also tested whether ceftriaxone administered only during self-administration attenuates the reinstatement of extinguished cocaine-seeking. We found that ceftriaxone did not affect the acquisition of cocaine self-administration but was able to attenuate reinstatement weeks after ceftriaxone administration ceased. This attenuation in reinstatement was accompanied by a restoration of GLT-1 expression in the nucleus accumbens. Ceftriaxone also attenuated locomotor behavior following the first cocaine injection and prevented the induction of cocaine but not caffeine sensitization. While ceftriaxone-treated animals did not sensitize to caffeine, they displayed reduced caffeine-induced locomotion following repeated caffeine treatment, indicating a possible dopaminergic effect of ceftriaxone. Taken together, these results indicate that ceftriaxone produces enduring changes in glutamate homeostasis in the nucleus accumbens which counteract addiction-related behaviors.

Dissociation of genetic and hormonal influences on sex differences in alcoholism-related behaviors

Differences between men and women in alcohol abuse prevalence have long been attributed to social and hormonal factors. It is, however, becoming apparent that sex differences in substance dependence are also influenced by genetic factors. Using a four core genotype mouse model that enables dissociation of chromosomal and gonadal sex, we show that habitual responding for alcohol reinforcement is mediated by sex chromosome complement independent of gonadal phenotype. After moderate instrumental training, chromosomal male (XY) mice became insensitive to outcome devaluation, indicating habitual responding. Chromosomal female (XX) mice remained sensitive to outcome devaluation, signifying goal-directed behavior. There was no effect of gonadal phenotype on habitual responding. Conversely, alcohol drinking was predicted by gonadal phenotype independent of sex chromosome complement. These results indicate that different alcoholism-related behaviors are determined independently by gonadal and chromosomal sex.