Cognitive reserve mediates the severity of certain neuropsychological deficits related to cocaine use disorder

Introduction: The concept of cognitive reserve (CR) is being considered in the field of substance use disorder (SUD) by observing that there are individuals whose brain alterations are not related to the cognitive symptomatology they present. Aims: Our aims were to characterise the possible neuropsychological deficits in a sample of subjects with SUD compared to a control group and to determine whether the degree of CR is a mediator in the cognitive functioning of these patients. Methods: To perform these objectives, the study involved a sample of subjects with SUD in outpatient treatment and a control group. A CR questionnaire and a comprehensive neuropsychological assessment were administered, and we also collected data related to drug consumption and psychological well-being. Results: The SUD group showed poorer performance compared to the control group in several cognitive domains (attention, declarative memory, executive functions and emotional perception), as well as in psychological comfort. Interestingly, we observed that the deficits found in attention, declarative memory and executive functions were mediated by the CR level of the participants, an effect that we did not observe in the rest of the variables registered. Conclusion: Our results suggest that long-term drug consumption leads to cognitive deficits and affects the psychological well-being of the subjects. Moreover, the CR should be taken into account during the assessment and rehabilitation of patients with SUD due to its protective role against certain neuropsychological deficits.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Long-lasting memory deficits in mice withdrawn from cocaine are concomitant with neuroadaptations in hippocampal basal activity, GABAergic interneurons and adult neurogenesis

Cocaine addiction disorder is notably aggravated by concomitant cognitive and emotional pathology that impedes recovery. We studied whether a persistent cognitive/emotional dysregulation in mice withdrawn from cocaine holds a neurobiological correlate within the hippocampus, a limbic region with a key role in anxiety and memory but that has been scarcely investigated in cocaine addiction research. Mice were submitted to a chronic cocaine (20 mg/kg/day for 12 days) or vehicle treatment followed by 44 drug-free days. Some mice were then assessed on a battery of emotional (elevated plus-maze, light/dark box, open field, forced swimming) and cognitive (object and place recognition memory, cocaine-induced conditioned place preference, continuous spontaneous alternation) behavioral tests, while other mice remained in their home cage. Relevant hippocampal features [basal c-Fos activity, GABA+, parvalbumin (PV)+ and neuropeptide Y (NPY)+ interneurons and adult neurogenesis (cell proliferation and immature neurons)] were immunohistochemically assessed 73 days after the chronic cocaine or vehicle protocol. The cocaine-withdrawn mice showed no remarkable exploratory or emotional alterations but were consistently impaired in all the cognitive tasks. All the cocaine-withdrawn groups, independent of whether they were submitted to behavioral assessment or not, showed enhanced basal c-Fos expression and an increased number of GABA+ cells in the dentate gyrus. Moreover, the cocaine-withdrawn mice previously submitted to behavioral training displayed a blunted experience-dependent regulation of PV+ and NPY+ neurons in the dentate gyrus, and neurogenesis in the hippocampus. Results highlight the importance of hippocampal neuroplasticity for the ingrained cognitive deficits present during chronic cocaine withdrawal

Highlighting the role of cognitive and brain reserve in the substance use disorder field

Author manuscriptBackground: Cognitive reserve (CR) refers to the ability of an individual to cope with brain pathology remaining free of cognitive symptoms. This protective factor has been related to compensatory and more efficient brain mechanisms involved in resisting brain damage. For its part, Brain reserve (BR) refers to individual differences in the structural properties of the brain which could also make us more resilient to suffer from neurodegenerative and mental diseases. Objective: This review summarizes how this construct, mainly mediated by educational level, occupational attainment, physical and mental activity, as well as successful social relationships, has gained scientific attention in the last years with regard to diseases, such as neurodegenerative diseases, stroke or traumatic brain injury. Nevertheless, although CR has been studied in a large number of disorders, few researches have addressed the role of this concept in drug addiction. Methods: We provide a selective overview of recent literature about the role of CR and BR in preventing substance use onset. Likewise, we will also discuss how variables involved in CR (healthy leisure, social support or job- related activities, among others) could be trained and included as complementary activities of substance use disorder treatments. Results: Evidence about this topic suggests a preventive role of CR and BR on drug use onset and when drug addiction is established, these factors led to less severe addiction-related problems, as well as better treatment outcomes. Conclusion: CR and BR are variables not taken yet into account in drug addiction. However, they could give us a valuable information about people at risk, as well as patient’s prognosis.This study was funded by grants from the Spanish Ministry of Economy and Competitiveness (MINECO, Agencia Estatal de Investigación) cofounded by the European Research Development Fund -AEI/FEDER, UE- (PSI2015-73156-JIN to E.C.O.; PSI2017-82604R to L.J.S.) and from University of Malaga (Plan Propio 2017 – ‘Ayudas para proyectos dirigidos por jóvenes investigadores’, PPIT.UMA.B1.2017/38 to P.S.P.). Author D.L.G.M. holds a ‘FPU’ grant from the Spanish Ministry of Education, Culture and Sports (code: FPU13/04819). Author E.C.O. holds a ‘Jóvenes Investigadores’ grant (code: PSI2015-73156-JIN) from the Spanish Ministry of Economy and Competitiveness (Agencia Estatal de Investigación) co-funded by FEDER, UE. Author P.S.P. holds a ‘Juan de la Cierva-formación’ grant from the Spanish Ministry of Economy, Industry and Competitiveness (code: FJCI-2015-23925)

Effects of palmitoylethanolamide in cocaine-induced behaviours

Aims. Cocaine addiction is a chronically relapsing disorder characterized by the compulsion to seek and take the drug. Previous investigations have demonstrated that several drugs of abuse, as cocaine, can alter the levels of lipid-based signalling molecules such as the N-acylethanolamines (NAEs). In addition, NAEs levels in the brain are sensitive to cocaine self-administration and extinction training. In this context, this study aimed to investigate the effect of repeated and acute palmitoylethanolamide (PEA), an endogenous NAE, on the behavioural effects of cocaine using mouse models of conditioned reward and psychomotor activation. Methods. Using male C57BL/6J mice, the ability of repeated PEA injections (1 or 10 mg/kg i.p) to modulate the development of a conditioned place preference (CPP) and behavioural sensitization (BS) induced by cocaine (20 mg/kg i.p.) was evaluated. In addition, the expression of cocaine-induced CPP and BS after acute PEA administration was also studied. Results. PEA (1 and 10 mg/kg i.p) significantly reduced the development of cocaine-induced BS, but did not modify the acquisition of cocaine-induced CPP. Furthermore, both doses of PEA were able to reduce the expression of BS and CPP. Conclusions. Altogether, these findings show that exogenous administration of PEA attenuated psychomotor activation and impaired the expression of CPP induced by cocaine. Our results may be relevant in order to understand the role of NAEs in the development and treatment of cocaine addiction.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech. PSI2013-44901-P, AP2010-2044, FPU13/04819, CD12/0045

Reduction of adult hippocampal neurogenesis modifies brain functional connectivity and enhances cocaine-seeking in mice

Recently, adult hippocampal neurogenesis has been proposed as a putative neuroplastic mechanism involved in those behavioural processes. In this work, we studied the effect of the inhibition of adult hippocampal neurogenesis using the DNA alkylating agent temozolomide (TMZ), in cocaine-induced conditioned place preference (CPP) behaviour. In a first experiment, we investigated both CPP acquisition/expression and the functional brain circuits underlying CPP expression in control and neurogenesis-reduced conditions by analysing c-Fos immunoreactivity (c-Fos IR) in hippocampal and extrahippocampal addiction-related areas. A second experiment was designed to study the involvement of adult-born neurons in the extinction and cocaine-induced reinstatement of drug-seeking in the CPP model. We performed two independent studies where adult hippocampal neurogenesis was inhibited either before or after the CPP was acquired. Our results showed that TMZ treatment had no effect on the acquisition of the cocaine-induced CPP, but c-Fos IR associated to the test trial (CPP expression) revealed an increased activity in some of the analysed brain areas in the CPP-TMZ mice. Correlational and multivariate analysis revealed that, under normal conditions, the hippocampus showed widespread functional connectivity with other brain areas and strongly contributed to the functional brain network associated with CPP expression. However, mice with reduced neurogenesis showed an alternative brain circuit. The results of the second experiment revealed that mice acquiring the cocaine-induced CPP under neurogenesis-reduced conditions were delayed in extinguishing their drug seeking behaviour. However, when neurogenesis was inhibited after CPP acquisition, extinction was not affected but an enhanced long-term CPP retention was found, suggesting that the role of the adult-born neurons may differ depending on whether they are generated before or after drug-contextual associations are established. Importantly, cocaine-induced reinstatement of CPP behaviour was increased in the TMZ mice, regardless of the time of neurogenesis inhibition.Universidad de Málaga. Andalucía Tech, Campus de Excelencia Internacional. Spanish Ministry of Economy and Competitiveness (PSI2013-44901-P to L.J.S.; Subprograma RETICS Red de Trastornos Adictivos RD12/0028/0001, to F.R.F.). Author E.C-O. holds a ‘Sara Borrell’ research contract from the Spanish Carlos III Health Institute, Spanish Ministry of Economy and Competitiviness (grant number CD12/00455). Author D.L.G-M. holds a ‘FPU’ grant from the Spanish Ministry of Education, Culture and Sports (grant number FPU13/04819)

Behavioral traits predicting cocaine-conditioned place reference in mice: role of anxiety adn the basolateral amygdala

Aims. The individual susceptibility to cocaine addiction, a factor of interest in the understanding and prevention of this disorder, may be predicted by certain behavioral traits. However, these are not usually taken into account in research, making it difficult to identify whether they are a cause or a consequence of drug use. Methods. Male C57BL/6J mice underwent a battery of behavioral tests (elevated plus maze, hole-board, novelty preference in the Y maze, episodic-like object recognition memory and forced swimming test), followed by a cocaine-conditioned place preference (CPP) training to assess the reinforcing effect of the drug. In a second study, we aimed to determine the existence of neurobiological differences between the mice expressing high or low CPP by studying the number of neurons in certain addiction-related structures: the medial prefrontal cortex, the basolateral amygdala and the ventral tegmental area. Results. Anxiety-like behaviors in the elevated plus maze successfully predicted the cocaine-CPP behavior, so that the most anxious mice were also more likely to search for cocaine in a CPP paradigm. In addition, these mice exhibited an increased number of neurons in the basolateral amygdala, a key structure in emotional response including anxiety expression, without differences in the others regions analyzed. Conclusions. Our results suggest a relevant role of anxiety as a psychological risk factor for cocaine vulnerability, with the basolateral amygdala as potential common neural center for both anxiety and addiction.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech. PSI2013-44901-P, FPU13/04819, CD12/00455, Red de Trastornos Adictivo

Pharmacogenetic inhibition of the infralimbic cortex promotes reinstatement of cocaine-context memories in mice.

Funding: PID2020-113806RB-I00, 08-2021-AREA3, B1-2020_06, FPU20/00908, PRE2018-085673, PREDOC_01094, POSTDOC_ 21_00222. II Plan Propio de Investigación, Transferencia y Divulgación Científica de la UMA.Relapse is one of the main problems concerning treatment of cocaine use disorder. It have been suggested that the infralimbic cortex (IL), a division of the medial prefrontal cortex, is involved in extinction and reinstatement of associative memories, including those involving drugs. However, more selective strategies are needed to elucidate the involvement of IL in the long-term maintenance of drug-related maladaptive behaviours. Here, we employed pharmacogenetics to assess the causal role of IL in the reinstatement of a cocaine-induced conditioned place preference (CPP). For this purpose, adult C57BL/6J mice received bilateral intra-IL microinjections of an adeno-associated viral (AAV) vector containing the hM4Di designed receptor (AAV5-CaMKII-hM4Di-mCherry; AAV-hM4Di, n=11) or a control vector (AAV5-CaMKII-mCherry; AAV-control, n=9) prior receiving training in the cocaine-induced CPP model. After habituation, animals received compartment-paired conditioning by increasing doses of cocaine (2-16 mg/kg/day, i.p.) and were tested for cocaine-CPP, after which they were subjected to forced CPP extinction and then re-tested for cocaine-CPP. On day 37 after AAV infusion, mice received Clozapine N-oxide (CNO, 5 mg/kg, i.p.) and 30 min later were tested for cocaine-primed (7.5 mg/kg, i.p.) CPP reinstatement. Ninety minutes after, animals were perfused, and brains dissected. Our results indicated that both groups acquired and subsequently extinguished cocaine-CPP. However, only the AAV-hM4Di group showed a significant preference for the cocaine-paired compartment during the CPP reinstatement test. Immunofluorescence analyses of c-Fos expression in IL revealed a decrease of ~60% in mCherry+/c-Fos+ co-labelling in the AAV-hM4Di group, suggesting reduced IL neural activity during CPP reinstatement. Therefore, our data suggests that the IL plays a causal role in relapse to cocaine-related maladaptive behaviours, highlighting its importance as a potential therapeutic target.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Selective modulation of the infralimbic cortex activity regulates reinstatement of cocaine-context associations in mice.

Mechanisms underlying relapse into cocaine are not yet fully understood. Animal studies suggest a pivotal involvement of the infralimbic (IL) division of the medial prefrontal cortex, but causal evidence is lacking. Here, we employed chemogenetics to selectively modulate the IL during reinstatement of cocaine-related behaviours in the conditioned place preference (CPP) model. To this aim, C57BL/6J mice (N = 28) received intra-IL microinjections of adenoassociated viral vectors containing either silencing (AAV5-CaMKIIα-hM4Di-mCherry) or stimulatory (AAV5-CaMKIIα-hM3Dq-mCherry) designer receptors, or a control vector (AAV5-CaMKIIα-mCherry). Animals were trained to acquire a CPP induced by increasing doses of cocaine (2-16 mg/kg) and later submitted to forced extinction. Four weeks after AAV infusion, mice received Clozapine N-oxide (5 mg/kg) 30 minutes before undergoing a cocaine-primed (7.5 mg/kg) CPP reinstatement test. Ninety minutes later animals were perfused, and brains dissected to analyse the expression of mCherry and c-Fos proteins in the IL. We found that CPP reinstatement was significantly increased after silencing IL compared to the control group, while blocked after selective stimulation of this brain region. In turn, immunofluorescence analyses revealed a ~0.5-fold decrease and a ~3-fold increase in mCherry /c-Fos co-labelling in AAV-hM4Di and AAV-hM3Dq groups (respectively) compared to the control group. Taken together, our data indicate that the IL is causally involved in the reinstatement of cocaine-related maladaptive behaviours and stands out as a target for modulation to prevent cocaine relapse.Funding: PID2020-113806RB-I00, B4-2023-16, FPU20/00908, PREDOC_01094, POSTDOC_ 21_00222. II Plan Propio de Investigación, Transferencia y Divulgación Científica de la Universidad de Málaga. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Neuroplastic and cognitive impairment in substance use disorders: a therapeutic potential of cognitive stimulation

Author manuscriptDrug addiction is a chronic and relapsing disorder in which repeated drug exposure compromises brain neuroplasticity. Brain areas normally involved in learning and goal- directed behaviors become corrupted, which may lead to cognitive deficits that coexist with other addiction symptoms and predict a worse treatment outcome. New learning experiences that are not motivated by drugs may improve both cognitive deficits and drug-induced symptoms by promoting adaptive neuroplastic changes that could alleviate or reverse those involved in addiction. The present review will focus on whether potentiating healthy cognitive function, either by formal cognitive training or non-drug related environmental experiences, could exert beneficial effects in the therapeutics of addiction. Although additional studies are needed, the available clinical and preclinical evidence suggests that cognitive stimulation may provide a valuable adjuvant intervention in drug addiction.This study was funded by grants from the Spanish Ministry of Economy and Competitiveness (Agencia Estatal de Investigación) co-founded by the European Research Development Fund-AEI/FEDER, UE- (PSI2015-73156-JIN to E.C.O.; PSI2017-82604R to L.J.S.), Red de Trastornos Adictivos (RD16/0017/0001 to F.R.F.), Plan Nacional sobre Drogas, Ministerio de Sanidad, Servicios Sociales e Igualdad (PNSD2015/047 to J.S.) and the University of Málaga (Plan Propio 2017 – ‘Ayudas para proyectos dirigidos por jóvenes investigadores’, PPIT.UMA.B1.2017/38 to P.S.P). Author P.S.P. holds a ‘Juan de la Cierva-formación’ grant from the Spanish Ministry of Economy, Industry and Competitiveness (code: FJCI-2015-23925). Author D.L.G.M. holds a ‘FPU’ grant from the Spanish Ministry of Education, Culture and Sports (code: FPU13/04819). Authors J.S., A.S. and F.J.P. hold ‘Miguel Servet’ grants (codes: CPII17/00024, CP14/00173 and CP14/00212, respectively) from the National System of Health-Instituto de Salud Carlos- III co-funded by FEDER, UE. Author E.C.O. holds a ‘Jóvenes Investigadores’ grant (code: PSI2015-73156-JIN) from the Spanish Ministry of Economy and Competitiveness (Agencia Estatal de Investigación) co-funded by FEDER, UE

The infralimbic cortex and the hippocampal CA1-Subiculum are functionally involved in the extinction of cocaine-context associationes in mice.

Funding: PID2020-113806RB-I00, 08-2021-AREA3, B1-2020_06, PREDOC_01094, PRE2018-085673, FPU20/00908, POSTDOC_ 21_00222. II Plan Propio de Investigación, Transferencia y Divulgación Científica de la Universidad de Málaga.Cocaine abuse is a health and social problem worldwide. Treatment seeking for cocaine use disorder is on the rise, and relapse prevention remains as a primary goal. Interventions based on extinction of cocaine-related associative memories are promising but so far have not been successful. In this sense, further research is needed to elucidate the neurobiological substrates of extinction learning. Here, we aimed to study the neural circuitry involved in extinction of cocaine-context associations in the Conditioned Place Preference (CPP) model. Adult C57BL/6J mice received habituation to the CPP apparatus followed by conditioning with increasing doses of cocaine (2, 4, 8 and 16 mg/kg/day). After testing for CPP acquisition, a group of mice was submitted to four sessions of forced extinction (CPP+EXT, n = 9) while another group was maintained at home-cage (CPP+ACQ, n = 6). Then, both conditions were retested for cocaine-CPP. Ninety minutes later, animals were perfused, and brains collected. Next, we analysed by immunohistochemistry the expression of c-Fos in a variety of addiction-related structures including the medial prefrontal cortex (prelimbic, infralimbic), the striatum (nucleus accumbens, caudate-putamen), the basolateral amygdala and the hippocampus. Our results indicated that both groups acquired cocaine-CPP, but only the CPP+EXT condition ceased to show preference for the cocaine-paired compartment during the CPP retest. Importantly, the CPP+EXT mice showed increased c-Fos expression in the infralimbic cortex (IL), and the hippocampal CA1-subiculum during the CPP retest, with no changes in the other brain areas examined. Multivariate analyses revealed a relationship between IL and CA1-subiculum activity and CPP extinction. This suggest that such structures are functionally involved in retrieval of extinction memory for cocaine-context associations, thus standing out as potential therapeutic targets.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech