Extended length of stay and related costs associated with dementia in acute care hospitals in Ireland.

OBJECTIVE: To estimate the additional impact of dementia on in-patient length of stay (LOS) and related costs in Irish acute hospitals. Both principal and secondary diagnosis effects are estimated and valued. METHODS: This is a cross-sectional study based on administrative data collected on all public hospital in-patient discharges in Ireland for people aged 65 years and older in 2019. Coarsened exact matching (CEM) was undertaken to account for observed confounders between dementia and non-dementia groups, while generalised linear modelling (GLM) was used to compare differences in LOS. RESULTS: Patients with a principal diagnosis of dementia spent on average 17.5 (CI: 15.42, 19.56; p < .01) d longer in hospital than similar patients with no principal diagnosis of dementia. LOS was 6.7 (CI: 6.31, 7.14; p < .01) d longer for patients with a secondary diagnosis of dementia compared to similar patients with no secondary diagnosis of dementia. The additional annual cost of care for patients in hospitals with a secondary (principal) diagnosis of dementia was €62.0 million (€13.2 million). CONCLUSIONS: This study highlights the economic impact of extended LOS for patients with dementia in Irish acute hospitals. Addressing specific dementia-related needs of people in hospital is likely to optimise resource use and decrease health care costs in acute care settings.

Increased kynurenine concentration attenuates serotonergic neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in rats through activation of aryl hydrocarbon receptor.

3,4-Methylenedioxymethamphetamine (MDMA) is an amphetamine derivative that has been shown to produce serotonergic damage in the brains of primates, including humans, and of rats. Tryptophan, the precursor of serotonin, is primarily degraded through the kynurenine (KYN) pathway, producing among others KYN, the main metabolite of this route. KYN has been reported as an endogenous agonist of the aryl hydrocarbon receptor (AhR), a transcription factor involved in several neurological functions. This study aims to determine the effect of MDMA on the KYN pathway and on AhR activity and to establish their role in the long-term serotonergic neurotoxicity induced by the drug in rats. Our results show that MDMA induces the activation of the KYN pathway, mediated by hepatic tryptophan 2,3-dioxygenase (TDO). MDMA also activated AhR as evidenced by increased AhR nuclear translocation and CYP1B1 mRNA expression. Autoradiographic quantification of serotonin transporters showed that both the TDO inhibitor 680C91 and the AhR antagonist CH-223191 potentiated the neurotoxicity induced by MDMA, while administration of exogenous l-kynurenine or of the AhR positive modulator 3,3'-diindolylmethane (DIM) partially prevented the serotonergic damage induced by the drug. The results demonstrate for the first time that MDMA increases KYN levels and AhR activity, and these changes appear to play a role in limiting the neurotoxicity induced by the drug. This work provides a better understanding of the physiological mechanisms that attenuate the brain damage induced by MDMA and identify modulation of the KYN pathway and of AhR as potential therapeutic strategies to limit the negative effects of MDMA.

Admission to long-stay residential care and mortality among people with and without dementia living at home but on the boundary of residential care: a competing risks survival analysis.

BACKGROUND: Health policy in many countries is underpinned by a commitment to support dependent older people to remain in their own home for as long as possible and practicable. This study explores factors affecting both admission to long-stay residential care (LSRC) and mortality among people with and without dementia who are currently living at home with intensive formal care support. METHODS: This is a cross-sectional study based on administrative data collected on 429 dependent older people in Ireland, 269 of whom were people with dementia. A cause-specific hazard model was used to investigate the hazard of admission to LSRC, while accounting for mortality as a competing risk and vice versa. RESULTS: Admission to LSRC was higher for people with dementia relative to people without and for those receiving lower amounts of informal care. The hazard of mortality was significantly higher for older people aged 85+, whereas it was lower for individuals with a medium level of dependency relative to those with high levels of dependency. The hazard of mortality was also influenced by the amount of informal care provision. CONCLUSION: People with dementia are more likely to be admitted to LSRC than people without. Care for people with dementia needs to be more specialised and personal, and intensity of provision should not be equated to the number of care hours on offer. Informal care provision may help to prevent admission to LSRC. Advanced age, physical dependency and informal care provision affect mortality, raising interesting issues in relation to resource allocation.

A comparison of self and proxy quality of life ratings for people with dementia and their carers: a European prospective cohort study.

Objectives: To identify correlates of self-rated and proxy-rated quality of life (QoL) in people with dementia on (i) a dementia-specific and (ii) a capability-wellbeing QoL measure at baseline and 12-month follow-up, and to consider such factors in the context of QoL intervention development.Method: Prospective clinical and demographic data were collected from 451 community-dwelling dyads (mild-moderate dementia) across eight European countries. QoL was measured using the QOL-AD and the ICECAP-O. Multivariate modelling identified correlates of self- and proxy-rated QoL at baseline and at 12-month follow-up.Results: Carer's proxy-ratings of QoL were significantly lower than self-ratings at all time-points for both measures. Proxy-ratings declined over time, but self-ratings remained stable. Baseline predictors of greater self-rated QoL were education, and greater functional ability and relationship quality. Greater proxy-rated QoL was associated with education and greater functional ability, relationship quality, carer social support and carer QoL, lower carer anxiety/depression and less severe neuropsychiatric symptoms in people with dementia. At follow-up, greater self-rated QoL was predicted by greater functional ability, relationship quality, carer social support and having a spousal carer. Greater proxy-rated QoL at follow-up was associated with the same factors as at baseline; however, the dyad living together was an additional predictive factor.Conclusion: Both proxy-ratings and self-ratings of QoL should be interpreted with caution and in the context of each individual caregiving relationship. Different functional, psychosocial, relational and contextual factors influence self- and proxy-ratings, and both sets of factors should be considered in the context of QoL intervention development for the dyad.

Estimates of the prevalence, incidence and severity of dementia in Ireland.

OBJECTIVES: In this paper we provide revised estimates of the prevalence of dementia in Ireland, the number of new cases per year and the severity mix. These estimates are a necessary input for any assessment of the potential demand for services and supports for people with dementia across all care settings in Ireland. METHODS: The prevalence, incidence and severity stage of dementia are calculated by applying rates from prominent international studies to population data from the 2016 census. RESULTS: We show that the total number of people with dementia in Ireland ranges between 39 272 and 55 266, depending on the international rates used to measure prevalence. The incidence of dementia in Ireland has increased as the population has aged, to at least 7752 new cases per year. We estimate that there are at least 11 175 people living at home in the community in Ireland with dementia who have a serious functional impairment, based on an Activities of Daily Living measurement, of which an estimated 1876 are chair or bedbound. CONCLUSIONS: Without a national prevalence study it is not possible to be precise about the estimates of the number of people with dementia in Ireland. However, having credible upper and lower bound estimates for the number of people with dementia, the potential number of new cases per year and severity rates is useful for planners and those charged with the responsibility of making resource allocation decisions in dementia.

Potentially modifiable determinants of malnutrition in older adults: A systematic review.

BACKGROUND & AIMS: Malnutrition in older adults results in significant personal, social, and economic burden. To combat this complex, multifactorial issue, evidence-based knowledge is needed on the modifiable determinants of malnutrition. Systematic reviews of prospective studies are lacking in this area; therefore, the aim of this systematic review was to investigate the modifiable determinants of malnutrition in older adults. METHODS: A systematic approach was taken to conduct this review. Eight databases were searched. Prospective cohort studies with participants of a mean age of 65 years or over were included. Studies were required to measure at least one determinant at baseline and malnutrition as outcome at follow-up. Study quality was assessed using a modified version of the Quality in Prognosis Studies (QUIPS) tool. Pooling of data in a meta-analysis was not possible therefore the findings of each study were synthesized narratively. A descriptive synthesis of studies was used to present results due the heterogeneity of population source and setting, definitions of determinants and outcomes. Consistency of findings was assessed using the schema: strong evidence, moderate evidence, low evidence, and conflicting evidence. RESULTS: Twenty-three studies were included in the final review. Thirty potentially modifiable determinants across seven domains (oral, psychosocial, medication and care, health, physical function, lifestyle, eating) were included. The majority of studies had a high risk of bias and were of a low quality. There is moderate evidence that hospitalisation, eating dependency, poor self-perceived health, poor physical function and poor appetite are determinants of malnutrition. Moderate evidence suggests that chewing difficulties, mouth pain, gum issues co-morbidity, visual and hearing impairments, smoking status, alcohol consumption and physical activity levels, complaints about taste of food and specific nutrient intake are not determinants of malnutrition. There is low evidence that loss of interest in life, access to meals and wheels, and modified texture diets are determinants of malnutrition. Furthermore, there is low evidence that psychological distress, anxiety, loneliness, access to transport and wellbeing, hunger and thirst are not determinants of malnutrition. There appears to be conflicting evidence that dental status, swallowing, cognitive function, depression, residential status, medication intake and/or polypharmacy, constipation, periodontal disease are determinants of malnutrition. CONCLUSION: There are multiple potentially modifiable determinants of malnutrition however strong robust evidence is lacking for the majority of determinants. Better prospective cohort studies are required. With an increasingly ageing population, targeting modifiable factors will be crucial to the effective treatment and prevention of malnutrition.

Malnutrition in Hospitalised Older Adults: A Multicentre Observational Study of Prevalence, Associations and Outcomes.

BACKGROUND: Malnutrition is common in older adults and is associated with high costs and adverse outcomes. The prevalence, predictors and outcomes of malnutrition on admission to hospital are not clear for this population. DESIGN: Prospective Cohort Study. SETTING: Six hospital sites (five public, one private). PARTICIPANTS: In total, 606 older adults aged 70+ were included. All elective and acute admissions to any speciality were eligible. Day-case admissions and those moribund on admission were excluded. MEASUREMENTS: Socio-demographic and clinical data, including nutritional status (Mini-Nutritional Assessment - short form), was collected within 36 hours of admission. Outcome data was collected prospectively on length of stay, in-hospital mortality and new institutionalisation. RESULTS: The mean age was 79.7; 51% were female; 29% were elective admissions; 67% were admitted to a medical specialty. Nutrition scores were available for 602/606; 37% had a 'normal' status, 45% were 'at-risk', and 18% were 'malnourished'. Malnutrition was more common in females, acute admissions, older patients and those who were widowed/ separated. Dementia, functional dependency, comorbidity and frailty independently predicted a) malnutrition and b) being at-risk of malnutrition, compared to normal status (p < .001). Malnutrition was associated with outcomes including an increased length of stay (p < .001), new institutionalisation (p =<0.001) and in-hospital mortality (p < .001). CONCLUSIONS: These findings support the prioritisation of nutritional screening in clinical practice and public health policy, for all patients ≥70 on admission to hospital, and in particular for people with dementia, increased functional dependency and/or multi-morbidity, and those who are frail.

A regional analysis of epidermal growth factor receptor (EGFR) mutated lung cancer for HSE South.

BACKGROUND: EGFR mutated lung cancer represents a subgroup with distinct clinical presentations, prognosis, and management requirements. We investigated the survival, prognostic factors, and real-world treatment of NSCLC patients with EGFR mutation in clinical practice. METHODS: A retrospective review of all specimens sent for EGFR analysis from December 2009 to September 2015 was performed. Patient demographics, specimen type, EGFR mutation status/type, stage at diagnosis, treatment, response rate, and survival data were recorded. RESULTS: 27/334 (8%) patient specimens sent for EGFR testing tested positive for a sensitising EGFR mutation. The median age was 65 years (40-85 years). Exon 19 deletion represented the most commonly detected alteration, accounting for 39% (n = 11). First-line treatment for those with Exon 18, 19, or 21 alterations (n = 24) was with an EGFR tyrosine kinase inhibitor (TKI) in 79% (n = 19). Objective response rate among these patients was 74% and median duration of response was 13 months (range 7-35 months). CONCLUSION: The incidence of EGFR mutation in our cohort of NSCLC is 9% which is consistent with mutation incidence reported in other countries. The rate of EGFR mutation in our population is slightly below that reported internationally, but treatment outcomes are consistent with published data. Real-world patient data have important contributions to make with regard to quality measurement, incorporating patient experience into guidelines and identifying safety signals.

A Study of the Patients Admitted to the Clinical Decision Unit over One Year.

Clinical decision units (CDUs) are areas within an emergency department (ED) providing care for the patient who may benefit from an extended observation period, usually for a maximum of twenty-four hours. A retrospective patient record audit was performed to determine the characteristics of patients admitted to the Cork University Hospital (CUH) CDU over 12 months. The average length of stay of a patient in the CDU was 29 hours. The most common diagnoses admitted to the CDU were chest pain (9.5%) and headache (7.2%). The research implies that the CDU provided a means for CUH to save approximately €2 million annually.

Antipsychotic prescription amongst hospitalized patients with dementia.

BACKGROUND: Antipsychotic drugs are used to treat behavioural and psychological symptoms of dementia, despite significant safety concerns regarding increased risk of stroke and mortality. The numbers of patients with dementia and related behavioural symptoms being treated in acute hospitals is increasing. AIM: (i) to determine pre-admission and in-hospital prevalence of antipsychotic use in a national sample of patients with dementia and acute illness; (ii) identify reasons for antipsychotic use; (iii) assess features of the ward environment which impact on patients with dementia; (iv) determine availability of dementia-specific policies, training, appraisal and mentorship programs which influence service delivery. DESIGN AND METHODS: Four-part standardized audit in 35 public acute hospitals comprising (i) retrospective healthcare record review (n = 660); (ii) prospective assessment of ward environment (n = 77); (iii) ward organization interview with clinical managers (n = 77); (iv) hospital organisation interview with senior managers (n = 35). RESULTS: Antipsychotic drugs were prescribed to 29% of patients with dementia before hospitalization and to 41% during hospitalization; one quarter received new or additional prescriptions. Assessments for delirium (45%), dementia symptoms (39%), mood (26%), mental state (64%) and distress-provoking factors (3%) were suboptimal. Drug indications were documented in 78%. Non-pharmacological interventions were not documented. Most wards lacked environmental cues to promote orientation. Dementia-specific care pathways existed in 2 of 35 hospitals. Staff support and training programmes were suboptimal. 12% of patients were discharged with new antipsychotic prescriptions. CONCLUSION: Antipsychotic medications are commonly prescribed for hospitalized patients with dementia in Ireland. Ward environments and dementia-related governance structures are suboptimal.

Insights into the pathophysiology of catch-up compared with non-catch-up growth in children born small for gestational age: an integrated analysis of metabolic and transcriptomic data.

Small for gestational age (SGA) children exhibiting catch-up (CU) growth have a greater risk of cardiometabolic diseases in later life compared with non-catch-up (NCU) SGA children. The aim of this study was to establish differences in metabolism and gene expression profiles between CU and NCU at age 4-9 years. CU children (n=22) had greater height, weight and body mass index standard deviation scores along with insulin-like growth factor-I (IGF-I) and fasting glucose levels but lower adiponectin values than NCU children (n=11; all P<0.05). Metabolic profiling demonstrated a fourfold decrease of urine myo-inositol in CU compared with NCU (P<0.05). There were 1558 genes differentially expressed in peripheral blood mononuclear cells between the groups (P<0.05). Integrated analysis of data identified myo-inositol related to gene clusters associated with an increase in insulin, growth factor and IGF-I signalling in CU children (P<0.05). Metabolic and transcriptomic profiles in CU SGA children showed changes that may relate to cardiometabolic risk.

The effects of dependence and function on costs of care for Alzheimer's disease and mild cognitive impairment in Ireland.

OBJECTIVE: To explore the incremental effects of patient dependence and function on costs of care for patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (MCI) in Ireland. METHODS: Cost analysis based on reported resource use for a cross-section of 100 community-based people with AD and MCI. Formal care included general practice visits, hospitalizations, outpatient clinic consultations, accident and emergency visits, respite care, meals on wheels services and other health and social care professional consultations. Informal care included time input provided by caregivers. Resource unit costs were applied to value formal care and the opportunity cost method was used to value informal care. Patient dependence on others was measured using the Dependence Scale and patient functional capacity using the Disability Assessment for Dementia scale. Multivariate regression analysis was used to model the cost of care. RESULTS: Both dependence and function were independently and significantly associated with total formal and informal care cost: a one point increase in dependence was associated with a €796 increase in total cost and a one point improvement in function with a €417 reduction in total cost over 6 months. Patient function was significantly associated with formal care costs, whereas patient function and dependence were both significantly associated with informal care costs. CONCLUSION: The costs of care for patients with AD and MCI in Ireland are substantial. Interventions that reduce patient dependence on others and functional decline may be associated with important economic benefits.

Planning dementia services: new estimates of current and future prevalence rates of dementia for Ireland.

OBJECTIVES: The paper provides new estimates of dementia prevalence at a national and local level in Ireland and new projections of future numbers of people with dementia. METHODS: The prevalence of dementia at a national and local level has been calculated by applying European Collaboration on Dementia (EuroCoDe) prevalence rates to data from the Census of Population 2006. The National Disability Survey has been used to estimate the number of people with Down syndrome and dementia. Projections of future numbers of people with dementia have been calculated by applying EuroCoDe prevalence rates to the most recently available population projections from the Central Statistics Office (CSO). RESULTS: It is estimated that there were 41 740 people with dementia in Ireland in 2006. Estimates show that there are clear regional differences in prevalence of dementia across Ireland, with the largest proportion of people with dementia in the West of Ireland, and the Dublin North Eastern region having the lowest share of dementia. Our best estimate is that there are 700 people with Down syndrome and dementia in Ireland. Applying EuroCoDe prevalence rates to the most recent CSO population projections shows that the prevalence of dementia in Ireland will increase to between 67 493 and 70 000 in 2021 and to between 140 580 and 147 000 in 2041. CONCLUSIONS: Although there are several limitations to these estimates, the data provide timely and useful information for planning effective health and social care services, as well as raising public and professional awareness about dementia at a national level.

Dopamine D(1) receptor deletion strongly reduces neurotoxic effects of methamphetamine.

Methamphetamine (METH) is a potent, highly addictive psychostimulant consumed worldwide. In humans and experimental animals, repeated exposure to this drug induces persistent neurodegenerative changes. Damage occurs primarily to dopaminergic neurons, accompanied by gliosis. The toxic effects of METH involve excessive dopamine (DA) release, thus DA receptors are highly likely to play a role in this process. To define the role of D(1) receptors in the neurotoxic effects of METH we used D(1) receptor knock-out mice (D(1)R(-/-)) and their WT littermates. Inactivation of D(1)R prevented METH-induced dopamine fibre loss and hyperthermia, and increases in gliosis and pro-inflammatory molecules such as iNOS in the striatum. In addition, D(1)R inactivation prevented METH-induced loss of dopaminergic neurons in the substantia nigra. To explore the relationship between hyperthermia and neurotoxicity, METH was given at high ambient temperature (29 °C). In this condition, D(1)R(-/-) mice developed hyperthermia following drug delivery and the neuroprotection provided by D(1)R inactivation at 23 °C was no longer observed. However, reserpine, which empties vesicular dopamine stores, blocked hyperthermia and strongly potentiated dopamine toxicity in D(1)R(-/-) mice, suggesting that the protection afforded by D(1)R inactivation is due to both hypothermia and higher stored vesicular dopamine. Moreover, electrical stimulation evoked higher DA overflow in D(1)R(-/-) mice as demonstrated by fast scan cyclic voltammetry despite their lower basal DA content, suggesting higher vesicular DA content in D(1)R(-/-) than in WT mice. Altogether, these results indicate that the D(1)R plays a significant role in METH-induced neurotoxicity by mediating drug-induced hyperthermia and increasing the releasable cytosolic DA pool.

Changes in the serotonergic system and in brain-derived neurotrophic factor distribution in the main olfactory bulb of pcd mice before and after mitral cell loss.

The serotonergic centrifugal system innervating the main olfactory bulb (MOB) plays a key role in the modulation of olfactory processing. We have previously demonstrated that this system suffers adaptive changes under conditions of a lack of olfactory input. The present work examines the response of this centrifugal system after mitral cell loss in the Purkinje cell degeneration (pcd) mutant mice. The distribution and density of serotonergic centrifugal axons were studied in the MOB of control and pcd mice, both before and after the loss of mitral cells, using serotonin (5-HT) and 5-HT transporter immunohistochemistry. Studies of the amount of 5-HT and its metabolite, 5-hydroxyindole acetic acid (5-HIAA), were performed by means of high-performance liquid chromatography (HPLC), and the relative amounts of brain-derived neurotrophin factor, BDNF, and its major receptor, tropomyosin-related kinase B (TrkB), were measured by Western blot. Our study revealed that the serotonergic system develops adaptive changes after, but not before, mitral cell loss. The lack of the main bulbar projection cells causes a decrease in the serotonergic input received by the MOB, whereas the number of serotonergic cells in the raphe nuclei remains constant. In addition, one of the molecules directly involved in serotonergic sprouting, the neurotrophin BDNF and its main receptor TrkB, underwent alterations in the MOBs of the pcd animals even before the loss of mitral cells. These data indicate that serotonergic function in the MOB is closely related to olfactory activity and that mitral cell loss induces serotonergic plastic responses.

Peer support for patients with type 2 diabetes: cluster randomised controlled trial.

OBJECTIVE: To test the effectiveness of peer support for patients with type 2 diabetes. DESIGN: Cluster randomised controlled. SETTING: 20 general practices in the east of the Republic of Ireland. PARTICIPANTS: 395 patients (192 in intervention group, 203 in control group) and 29 peer supporters with type 2 diabetes. INTERVENTION: All practices introduced a standardised diabetes care system. The peer support intervention ran over a two year period and contained four elements: the recruitment and training of peer supporters, nine group meetings led by peer supporters in participant's own general practice, and a retention plan for the peer supporters. MAIN OUTCOME MEASURES: HbA(1c); cholesterol concentration; systolic blood pressure; and wellbeing score. RESULTS: There was no difference between intervention and control patients at baseline. All practices and 85% (337) of patients were followed up. At two year follow-up, there were no significant differences in HbA(1c) (mean difference -0.08%, 95% confidence interval -0.35% to 0.18%), systolic blood pressure (-3.9 mm Hg, -8.9 to 1.1 mm Hg), total cholesterol concentration (-0.03 mmol/L, -0.28 to 0.22 mmol/L), or wellbeing scores (-0.7, -2.3 to 0.8). While there was a trend towards decreases in the proportion of patients with poorly controlled risk factors at follow-up, particularly for systolic blood pressure (52% (87/166) >130 mm Hg in intervention v 61% (103/169) >130 mm Hg in control), these changes were not significant. The process evaluation indicated that the intervention was generally delivered as intended, though 18% (35) of patients in the intervention group never attended any group meetings. CONCLUSIONS: A group based peer support intervention is feasible in general practice settings, but the intervention was not effective when targeted at all patients with type 2 diabetes. While there was a trend towards improvements of clinical outcomes, the results do not support the widespread adoption of peer support. Trial registration Current Controlled Trials ISRCTN42541690.

Involvement of 2-arachidonoyl glycerol in the increased consumption of and preference for ethanol of mice treated with neurotoxic doses of methamphetamine.

BACKGROUND AND PURPOSE: Methamphetamine (METH) is a psychostimulant amphetamine that causes long-term dopaminergic neurotoxicity in mice. Hypodopaminergic states have been demonstrated to increase voluntary ethanol (EtOH) consumption and preference. In addition, the endocannabinoid system has been demonstrated to modulate EtOH drinking behaviour. Thus, we investigated EtOH consumption in METH-lesioned animals and the role of cannabinoid (CB) signalling in this EtOH drinking. EXPERIMENTAL APPROACH: Mice were treated with a neurotoxic regimen of METH, and 7 days later exposed to increasing concentrations of drinking solutions of EtOH (3, 6, 10 and 20%). Seven days after neurotoxic METH, the following biochemical determinations were carried out in limbic forebrain: CB(1) receptor density and stimulated activity, 2-arachidonoyl glycerol (2-AG) and monoacylglycerol lipase (MAGL) activity, dopamine levels and dopamine transporter density. KEY RESULTS: EtOH consumption and preference were increased in METH-treated mice. Seven days after METH, a time at which both dopamine levels and density of dopamine transporters in limbic forebrain were decreased, CB(1) receptor density and activity were unaltered, but 2-AG levels were increased. At this same time-point, MAGL activity was reduced. The CB(1) receptor antagonist AM251 prevented the METH-induced increase in EtOH consumption and preference, while N-arachidonoyl maleimide, an inhibitor of MAGL, increased EtOH consumption and preference in both saline- and METH-treated mice. CONCLUSIONS AND IMPLICATIONS: An increase in endocannabinoid tone may be involved in the increased consumption of and preference for EtOH displayed by METH-lesioned mice as blockade of the CB(1) receptor decreased EtOH-seeking behaviours, whereas the MAGL inhibitor increased EtOH consumption.

Dopamine transporter down-regulation following repeated cocaine: implications for 3,4-methylenedioxymethamphetamine-induced acute effects and long-term neurotoxicity in mice.

BACKGROUND AND PURPOSE: 3,4-Methylenedioxymethamphetamine (MDMA) and cocaine are two widely abused psychostimulant drugs targeting the dopamine transporter (DAT). DAT availability regulates dopamine neurotransmission and uptake of MDMA-derived neurotoxic metabolites. We aimed to determine the effect of cocaine pre-exposure on the acute and long-term effects of MDMA in mice. EXPERIMENTAL APPROACH: Mice received a course of cocaine (20 mg*kg(-1), x2 for 3 days) followed by MDMA (20 mg*kg(-1), x2, 3 h apart). Locomotor activity, extracellular dopamine levels and dopaminergic neurotoxicity were determined. Furthermore, following the course of cocaine, DAT density in striatal plasma membrane and endosome fractions was measured. KEY RESULTS: Four days after the course of cocaine, challenge with MDMA attenuated the MDMA-induced striatal dopaminergic neurotoxicity. Co-administration of the protein kinase C (PKC) inhibitor NPC 15437 prevented cocaine protection. At the same time, after the course of cocaine, DAT density was reduced in the plasma membrane and increased in the endosome fraction, and this effect was prevented by NPC 15437. The course of cocaine potentiated the MDMA-induced increase in extracellular dopamine and locomotor activity, following challenge 4 days later, compared with those pretreated with saline. CONCLUSIONS AND IMPLICATIONS: Repeated cocaine treatment followed by withdrawal protected against MDMA-induced dopaminergic neurotoxicity by internalizing DAT via a mechanism which may involve PKC. Furthermore, repeated cocaine followed by withdrawal induced behavioural and neurochemical sensitization to MDMA, measures which could be indicative of increased rewarding effects of MDMA.