Molecular Characterization of Severe Acute Respiratory Syndrome Coronavirus 2 Isolates From Central Inner Sardinia.

BACKGROUND: The SARS-CoV-2 pandemic stimulated an outstanding global sequencing effort, which allowed to monitor viral circulation and evolution. Nuoro province (Sardinia, Italy), characterized by a relatively isolated geographical location and a low population density, was severely hit and displayed a high incidence of infection. METHODS: Amplicon approach Next Generation Sequencing and subsequent variant calling in 92 respiratory samples from SARS-CoV-2 infected patients involved in infection clusters from March 2020 to May 2021. RESULTS: Phylogenetic analysis displayed a coherent distribution of sequences in terms of lineage and temporal evolution of pandemic. Circulating lineage/clade characterization highlighted a growing diversity over time, with an increasingly growing number of mutations and variability of spike and nucleocapsid proteins, while viral RdRp appeared to be more conserved. A total of 384 different mutations were detected, of which 196 were missense and 147 synonymous ones. Mapping mutations along the viral genome showed an irregular distribution in key genes. S gene was the most mutated gene with missense and synonymous variants frequencies of 58.8 and 23.5%, respectively. Mutation rates were similar for the S and N genes with one mutation every ∼788 nucleotides and every ∼712 nucleotides, respectively. Nsp12 gene appeared to be more conserved, with one mutation every ∼1,270 nucleotides. The frequency of variant Y144F in the spike protein deviated from global values with higher prevalence of this mutation in the island. CONCLUSION: The analysis of the 92 viral genome highlighted evolution over time and identified which mutations are more widespread than others. The high number of sequences also permits the identification of subclusters that are characterized by subtle differences, not only in terms of lineage, which may be used to reconstruct transmission clusters. The disclosure of viral genetic diversity and timely identification of new variants is a useful tool to guide public health intervention measures.

Adolescent cannabis exposure increases heroin reinforcement in rats genetically vulnerable to addiction.

On the basis of epidemiological studies it has been proposed that cannabis use plays a causal role in the abuse of highly addictive drugs (Gateway Hypothesis). However, epidemiological studies are intrinsically unable to provide evidence of causality. Experimental studies can provide this evidence but they are feasible only in animal models and to date such evidence is lacking. In view of the importance of genetic factors in drug abuse, we investigated the influence of adolescent cannabis exposure on adult heroin reinforcement in two inbred rat strains differentially vulnerable to drugs of abuse, addiction prone Lewis (LEW) and addiction resistant Fischer 344 (F344) strains. Male LEW and F344 rats aged six weeks were exposed to increasing Δ9-tetrahydrocannabinol (THC) doses, twice a day for 3 days (2, 4, 8 mg/kg, i.p.). At adulthood they were allowed to self-administer heroin (0.025 mg/kg) under both Fixed- (FR) and Progressive- (PR) ratio schedules of responding. Following extinction, responding was reinstated by drug-cues and/or by heroin priming. THC pre-exposure increased responding for heroin and heroin intake under FR-3 and FR-5 as well as PR protocols and increased breaking point in PR schedules in LEW but not F344 rats. Drug cues and heroin priming reinstated responding in LEW and F344, but THC pre-exposure increased reinstatement by priming in LEW rats and by cues in F344 rats. These observations show that in genetically predisposed individuals, adolescent cannabis exposure increases heroin reinforcing properties, thus providing a mechanism for a causal role of adolescent cannabis use in heroin abuse.

Early Diffusion of SARS-CoV-2 Infection in the Inner Area of the Italian Sardinia Island.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for the coronavirus disease 2019 (COVID-19) pandemic, which started as a severe pneumonia outbreak in Wuhan, China, in December 2019. Italy has been the first European country affected by the pandemic, registering a total of 300,363 cases and 35,741 deaths until September 24, 2020. The geographical distribution of SARS-CoV-2 in Italy during early 2020 has not been homogeneous, including regions severely affected as well as administrative areas being only slightly interested by the infection. Among the latter, Sardinia represents one of the lowest incidence areas likely due to its insular nature. METHODS: Next-generation sequencing of a small number of complete viral genomes from clinical samples and their virologic and phylogenetic characterization was performed. RESULTS: We provide a first overview of the SARS-CoV-2 genomic diversity in Sardinia in the early phase of the March-May 2020 pandemic based on viral genomes isolated in the most inner regional hospital of the island. Our analysis revealed a remarkable genetic diversity in local SARS-CoV-2 viral genomes, showing the presence of at least four different clusters that can be distinguished by specific amino acid substitutions. Based on epidemiological information, these sequences can be linked to at least eight different clusters of infection, four of which likely originates from imported cases. In addition, the presence of amino acid substitutions that were not previously reported in Italian patients has been observed, asking for further investigations in a wider population to assess their prevalence and dynamics of emergence during the pandemic. CONCLUSION: The present study provides a snapshot of the initial phases of the SARS-CoV-2 infection in inner area of the Sardinia Island, showing an unexpected genomic diversity.

The Roman high- and low-avoidance rats differ in the sensitivity to shock-induced suppression of drinking and to the anxiogenic effect of pentylenetetrazole.

The Roman high- (RHA) and low-avoidance (RLA) outbred rat lines are selected for respectively rapid vs. poor acquisition of active avoidant behavior. Emotional reactivity appears to be the most prominent behavioral difference between the two lines, with RLA rats being more fearful/anxious than their RHA counterparts. Accordingly, here we show that shock-induced inhibition of drinking behavior in the Vogel's test is significantly more pronounced in RLA than RHA rats. Thus, unpunished drinking activity is similar in both lines (38.1 ±â€¯0.9 and 36.4 ±â€¯0.6 licking periods/3 min in RLA and RHA rats, respectively), whereas under punished conditions (0.05-1.00 mA electric shocks delivered through the drinking tube) a more robust decrease in drinking behavior is observed in RLA vs. RHA rats. Moreover, fear-related behaviors like freezing and self-grooming are more frequent in RLA than RHA rats throughout the test. Similar results are obtained with the inbred RHA-I and RLA-I rats, which have been selected and bred through brother/sister mating of the outbred lines. In keeping with the above findings, we also show that, compared with their RHA counterparts, the outbred RLA rats are similarly responsive to the anticonflict effect of diazepam but more responsive to the proconflict effect of pentylenetetrazole in the Vogel's test. Collectively, these results reveal another behavioral trait distinguishing RHA from RLA rats and add experimental support to the view that the Roman lines/strains are a valid genetic model for the study of the neural underpinnings of fear/anxiety- and stress-related behaviors.

Pomalidomide in heavily pretreated refractory multiple myeloma: a case report.

We present the case of a 70-year-old man diagnosed with multiple myeloma in 2008, who after four therapy lines initiated a fifth-line treatment with pomalidomide (4 mg orally, days 1-21 of a 28-day cycle) and low-dose dexamethasone (40 mg weekly orally). The patient was treated with pomalidomide for almost 2 years achieving a complete remission after 12 cycles. Complete remission was maintained for 9 months. This case illustrates the potential of pomalidomide plus low-dose dexamethasone to overcome multiple myeloma refractoriness inducing a quick and very prolonged remission.

A survey on lifestyle and level of biomarkers of environmental exposure in residents in Civitavecchia (Italy).

BACKGROUND: The assessment of individual exposure to toxicants in industrially contaminated areas is difficult when multiple productions are active close to residential areas. Two thermoelectric power plants and a large harbor have been operating since the '60s in the area of Civitavecchia (North of Rome). METHODS: The ABC (Ambiente e Biomonitoraggio nell'area di Civitavecchia, Environment and Biomonitoring in Civitavecchia) program involved, in the period 2013-2014, residents in Civitavecchia and in the nearby municipalities (Santa Marinella, Allumiere, Tolfa and Tarquinia). They were randomly selected from the Municipal Register's data and their residence addresses were geocoded using GIS techniques. Biomonitoring of the following urinary metals, Sb, Be, Mo, Cd, Sn, W, Ir, Pt, Hg, Tl, V, Cr, Mn, Co, Ni, Cu, Zn, Rh, Pd, As were performed. Glucose and lipid metabolism, liver, renal, and endocrine function were evaluated through blood laboratory tests. Tests of lung functionwere also carried out as well as saturometry (oxygen rate in the blood with an illuminated sensor placed on the fingertip), anthropometric and blood pressure measurements. Information on individual characteristics, histories of exposure, such as the consumption of local food, occupational history, lifestyle and medical history were collected through a validated questionnaire. Samples of nails and hair were also collected. The biological material (blood, urine, nails and hair) was stored in a biobank for future analysis related to the possible mechanisms of biological damage. The study protocol received the approval of the local ethics committee. RESULTS: A total of 1177 residents were enrolled (58% female, 60% with a secondary or graduate school degree). No particular differences in metal concentrations based on the municipality of residence were observed. For arsenic, mercury, lead, and tungsten some differences between the two geographical areas were observed, probably due to different diet, lifestyle (e.g., alcohol consumption, smoking, use of jewelry and piercings, tattoos, physical activity, hormonal and mineral supplements, and drugs), and occupational exposure. CONCLUSIONS: The undergoing study on the association between biomarkers concentration and pollutants concentrations - estimated using a dispersion modeling approach, and adjusting for personal characteristics and concomitant other environmental exposure - could clarify the individual exposure of the residents in this industrial area.

Caffeine, a common active adulterant of cocaine, enhances the reinforcing effect of cocaine and its motivational value.

RATIONALE: Caffeine is one of the psychoactive substances most widely used as an adulterant in illicit drugs, such as cocaine. Animal studies have demonstrated that caffeine is able to potentiate several cocaine actions, although the enhancement of the cocaine reinforcing property by caffeine is less reported, and the results depend on the paradigms and experimental protocols used. OBJECTIVES: We examined the ability of caffeine to enhance the motivational and rewarding properties of cocaine using an intravenous self-administration paradigm in rats. Additionally, the role of caffeine as a primer cue during extinction was evaluated. METHODS: In naïve rats, we assessed (1) the ability of the cocaine (0.250-0.125 mg/kg/infusion) and caffeine (0.125-0.0625 mg/kg/infusion) combination to maintain self-administration in fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement compared with cocaine or caffeine alone and (2) the effect of caffeine (0.0625 mg/kg/infusion) in the maintenance of responding in the animals exposed to the combination of the drugs during cocaine extinction. RESULTS: Cocaine combined with caffeine and cocaine alone was self-administered on FR and PR schedules of reinforcement. Interestingly, the breaking point determined for the cocaine + caffeine group was significantly higher than the cocaine group. Moreover, caffeine, that by itself did not maintain self-administration behavior in naïve rats, maintained drug-seeking behavior of rats previously exposed to combinations of cocaine + caffeine. CONCLUSIONS: Caffeine enhances the reinforcing effects of cocaine and its motivational value. Our results highlight the role of active adulterants commonly used in cocaine-based illicit street drugs.

Reassessing the Evolutionary History of the 17q21 Inversion Polymorphism.

A polymorphic inversion that lies on chromosome 17q21 comprises two major haplotype families (H1 and H2) that not only differ in orientation but also in copy-number. Although the processes driving the spread of the inversion-associated lineage (H2) in humans remain unclear, a selective advantage has been proposed for one of its subtypes. Here, we genotyped a large panel of individuals from previously overlooked populations using a custom array with a unique panel of H2-specific single nucleotide polymorphisms and found a patchy distribution of H2 haplotypes in Africa, with North Africans displaying a higher frequency of inverted subtypes, when compared with Sub-Saharan groups. Interestingly, North African H2s were found to be closer to "non-African" chromosomes further supporting that these populations may have diverged more recently from groups outside Africa. Our results uncovered higher diversity within the H2 family than previously described, weakening the hypothesis of a strong selective sweep on all inverted chromosomes and suggesting a rather complex evolutionary history at this locus.

Impairment of acquisition of intravenous cocaine self-administration by RNA-interference of dopamine D1-receptors in the nucleus accumbens shell.

Microdialysis during i.v. drug self-administration (SA) have implicated nucleus accumbens (NAc) shell DA in cocaine and heroin reinforcement. However, this correlative evidence has not been yet substantiated by experimental evidence obtained by studying the effect of selective manipulation of NAc shell DA transmission on cocaine and heroin SA. In order to investigate this issue, DA D1a receptor (D1aR) expression was impaired in the NAc shell and core by locally infusing lentiviral vectors (LV) expressing specific D1aR-siRNAs (LV-siRNAs). Control rats were infused in the same areas with LV expressing GFP. Fifteen days later, rats were trained to acquire i.v. cocaine or heroin self-administration (SA). At the end of behavioral experiments, in order to evaluate the effect of LV-siRNA on D1aR expression, rats were challenged with amphetamine and the brains were processed for immunohistochemical detection of c-Fos and D1aR. Control rats acquired i.v. cocaine and heroin SA. Infusion of LV-siRNAs in the medial NAc shell reduced D1aR density and the number of c-Fos positive nuclei in the NAc shell, while sparing the core, and prevented the acquisition of cocaine, but not heroin SA. In turn, LV-siRNAs infusion in the core reduced D1aR density and the number of c-Fos positive nuclei in the same area, while sparing the shell, and failed to affect acquisition of cocaine. The differential effect of LV impairment of NAc shell D1aR on cocaine and heroin SA indicates that NAc shell DA acting on D1aR specifically mediates cocaine reinforcement.

Methylation analysis of the phosphates and tensin homologue on chromosome 10 gene (PTEN) in multiple myeloma.

BACKGROUND: Aberrant DNA methylation of promoter region CpG islands is an alternative mechanism that leads to genetic defects in the inactivation of tumor suppressor genes during myelomagenesis. The aim of this study was to examine the promoter methylation status of the phosphates and tensin homologue on chromosome 10 (PTEN) gene in a cohort of multiple myeloma patients. FINDINGS: The PTEN gene was hypermethylated in 7 out of 58 (12%) primary myeloma samples. The correlation between functional inactivation and PTEN mRNA levels was not statistically significant. The multiple myeloma subgroup with an aberrant PTEN status had a prevalence of the component IgG, Salmon Durie stage I, lower lactate dehydrogenase levels, intermediate-standard cytogenetic risk and longer overall survival with the respect to the unmethylated subgroup. CONCLUSIONS: This is the first report demonstrating the presence of PTEN promoter hypermethylation in multiple myeloma.

Effects of chronic antidepressant treatments in a putative genetic model of vulnerability (Roman low-avoidance rats) and resistance (Roman high-avoidance rats) to stress-induced depression.

INTRODUCTION: The Roman low- (RLA) and high-avoidance (RHA) rats were selectively bred for, respectively, poor versus rapid acquisition of active avoidance in a shuttle box and, under aversive conditions, display reactive (RLA) versus proactive (RHA) coping behaviors. In the forced swim test (FST), RLA rats exhibit a depression-like behavior characterized by greater immobility and fewer climbing counts when compared with their RHA counterparts. Furthermore, subacute treatments with clinically effective antidepressant drugs decrease immobility and increase climbing or swimming in RLA rats but do not modify the performance of RHA rats. OBJECTIVE AND METHODS: Because chronic treatment with antidepressants is usually required to produce clinical effects, the present study was designed to compare the behaviors of RLA and RHA rats in the FST after subacute (1 day) and chronic (15 days) administration of desipramine, fluoxetine, and chlorimipramine. RESULTS: In RLA rats, subacute treatments with low doses of desipramine, fluoxetine, and chlorimipramine (2.5-5 mg/kg) were ineffective whereas chronic treatments with the same doses of all three antidepressants decreased immobility and also increased climbing (desipramine) or swimming (fluoxetine). By contrast, neither subacute nor chronic treatments with these antidepressants induced significant changes in the behavior of RHA rats in the FST. CONCLUSIONS: RLA and RHA rats represent two divergent phenotypes, respectively susceptible and resistant to develop depression-like behavior under aversive environmental conditions that may be used to identify genetically determined neural substrates and mechanisms underlying vulnerability and resistance to stress-induced depression.

Walking four times weekly for at least 15 min is associated with longevity in a cohort of very elderly people.

OBJECTIVES: This study investigated the role of walking outdoors on longevity, controlling for individual and other life-style factors as possible confounders. METHODS: A 10-year cohort study was conducted with 152 self-caring and mobile, mean age 80 years, were enrolled in the study. Information on socio-demographic characteristics, clinical and biochemical data, diet, physical activity, smoking, depression status, cognitive status and anthropometrics measurements, were obtained for all participants. Cox proportional-hazards models were used to determine independent predictors of longevity. RESULTS: During the 10-years of follow-up, 96 (63%) died. Old age, chronic diseases, smoking, depression, CD4/CD8 ratio and coffee consumption were significantly predictors of mortality. Over-all survival was highest for subjects walking at open air for 4 times weekly for at least 15 min in comparison to subjects walking less than 4 times weekly (40% versus 22%). After adjusting for sex, age, education, chronic diseases, smoking, Body Mass Index and CD4/CD8 ratio, elderly people walking at open air for four times weekly had 40% decreased risk of mortality that individuals who walked less than four times weekly [relative risk (RR)=0.53; 95% confidence interval (CI)=0.32-0.88, p=0.01]. CONCLUSIONS: Findings suggest an independent and protective effect of walking on mortality and supports the encouragement of physical activity in advanced age for increasing longevity.

Dissecting the genetic make-up of North-East Sardinia using a large set of haploid and autosomal markers.

Sardinia has been used for genetic studies because of its historical isolation, genetic homogeneity and increased prevalence of certain rare diseases. Controversy remains concerning the genetic substructure and the extent of genetic homogeneity, which has implications for the design of genome-wide association studies (GWAS). We revisited this issue by examining the genetic make-up of a sample from North-East Sardinia using a dense set of autosomal, Y chromosome and mitochondrial markers to assess the potential of the sample for GWAS and fine mapping studies. We genotyped individuals for 500K single-nucleotide polymorphisms, Y chromosome markers and sequenced the mitochondrial hypervariable (HVI-HVII) regions. We identified major haplogroups and compared these with other populations. We estimated linkage disequilibrium (LD) and haplotype diversity across autosomal markers, and compared these with other populations. Our results show that within Sardinia there is no major population substructure and thus it can be considered a genetically homogenous population. We did not find substantial differences in the extent of LD in Sardinians compared with other populations. However, we showed that at least 9% of genomic regions in Sardinians differed in LD structure, which is helpful for identifying functional variants using fine mapping. We concluded that Sardinia is a powerful setting for genetic studies including GWAS and other mapping approaches.

Household contact with pets and birds and risk of lymphoma.

BACKGROUND: Contact with household pets has been suggested to be inversely associated with lymphoma risk. METHODS: We tested the hypothesis in a case-control study of lymphoma in the Sardinia region of Italy. Cases were 326 patients, first diagnosed with lymphoma in 1999-2003. Controls were 464 population controls, frequency matched to cases by age, gender, and area of residence. In person interviews included self-reported household contact with pets and birds, type of pet(s), and age at starting contact. RESULTS: Frequent contact with birds was inversely associated with lymphoma, and particularly B-cell non-Hodgkin lymphoma (odds ratio [OR] = 0.6, 95% confidence interval [95% CI]: 0.4, 0.9). Contact with chickens accounted for this inverse association, which was strongest for first contact occurring at age ≤8 years (OR = 0.4, 95% CI: 0.2, 1.0). No association was observed when first contact occurred at age 9 or older. Contact with any pets was inversely associated with risk of diffuse large B-cell lymphoma (OR = 0.4, 95% CI: 0.2, 1.0), but not other lymphoma subtypes. CONCLUSION: Our results support the hypothesis that early-life exposure to pets, birds and particularly with chickens might be associated with a reduced risk of lymphoma.

Protein tyrosine phosphatase receptor type {gamma} is a functional tumor suppressor gene specifically downregulated in chronic myeloid leukemia.

Chronic myelogenous leukemia (CML) is the most common myeloproliferative disease. Protein tyrosine phosphatase receptor type γ (PTPRG) is a tumor suppressor gene and a myeloid cell marker expressed by CD34(+) cells. Downregulation of PTPRG increases colony formation in the PTPRG-positive megakaryocytic cell lines MEG-01 and LAMA-84 but has no effect in the PTPRG-negative cell lines K562 and KYO-1. Its overexpression has an oncosuppressive effect in all these cell lines and is associated with myeloid differentiation and inhibition of BCR/ABL-dependent signaling. The intracellular domain of PTPRG directly interacts with BCR/ABL and CRKL, but not with signal transducers and activators of transcription 5. PTPRG is downregulated at the mRNA and protein levels in leukocytes of CML patients in both peripheral blood and bone marrow, including CD34(+) cells, and is reexpressed following molecular remission of disease. Reexpression was associated with a loss of methylation of a CpG island of PTPRG promoter occurring in 55% of the patients analyzed. In K562 cell line, the DNA hypomethylating agent 5-aza-2'-deoxycytidine induced PTPRG expression and caused an inhibition of colony formation, partially reverted by downregulation of PTPRG expression. These findings establish, for the first time, PTPRG as a tumor suppressor gene involved in the pathogenesis of CML, suggesting its use as a potential diagnostic and therapeutic target.

Effects of antidepressants on the performance in the forced swim test of two psychogenetically selected lines of rats that differ in coping strategies to aversive conditions.

INTRODUCTION: The selective breeding of Roman low-avoidance (RLA) and high-avoidance (RHA) rats for, respectively, poor versus rapid acquisition of active avoidance in a shuttle-box has produced two phenotypes that differ drastically in the reactivity to stressful stimuli: in tests used to assess emotionality, RLA rats display passive ("reactive") coping and robust hypothalamus-pituitary-adrenal (HPA) axis reactivity, whereas RHA rats show proactive coping and blunted HPA axis responses. The behavioral and neuroendocrine traits that distinguish these lines suggest that RLA rats may be prone, whereas RHA rats may be resistant to develop depression-like behavior when exposed to stressful experimental conditions. OBJECTIVE AND METHODS: To evaluate the performance of the Roman lines in the forced swim test, immobility, climbing, and swimming were assessed under baseline conditions (i.e., pretest in naïve animals or test after the administration of vehicle), and after subacute treatment with desipramine, fluoxetine, and chlorimipramine. RESULTS: Under baseline conditions, RLA rats displayed greater immobility and fewer climbing counts than RHA rats. In RLA rats, desipramine, fluoxetine, and chlorimipramine decreased immobility; moreover, desipramine and chlorimipramine increased climbing, whereas fluoxetine increased swimming. In RHA rats, none of these drugs affected immobility, swimming, or climbing. CONCLUSIONS: RLA and RHA rats represent two divergent phenotypes respectively susceptible and resistant to display depression-like behavior in the forced swim test. Hence, comparative studies in these lines may help to develop novel working hypotheses on the relationships among genotype, temperament traits, and neural mechanisms underlying the vulnerability or resistance to stress-induced depression in humans.

A role of BRCA1 and BRCA2 germline mutations in breast cancer susceptibility within Sardinian population.

BACKGROUND: In recent years, numerous studies have assessed the prevalence of germline mutations in BRCA1 and BRCA2 genes in various cohorts. We here extensively investigated the prevalence and geographical distribution of BRCA1-2 mutations in the entire genetically-homogeneous Sardinian population. The occurrence of phenotypic characteristics which may be predictive for the presence of BRCA1-2 germline mutations was also evaluated. METHODS: Three hundred and forty-eight breast cancer patients presenting a familial recurrence of invasive breast or ovarian carcinoma with at least two affected family members were screened for BRCA1-2 mutations by DHPLC analysis and DNA sequencing. Association of BRCA1 and BRCA2 mutational status with clinical and pathological parameters was evaluated by Pearson's Chi-Squared test. RESULTS AND CONCLUSION: Overall, 8 BRCA1 and 5 BRCA2 deleterious mutations were detected in 35/348 (10%) families; majority (23/35;66%) of mutations was found in BRCA2 gene. The geographical distribution of BRCA1-2 mutations was related to three specific large areas of Sardinia, reflecting its ancient history: a) the Northern area, linguistically different from the rest of the island (where a BRCA2 c.8764_8765delAG mutation with founder effect was predominant); b) the Middle area, land of the ancient Sardinian population (where BRCA2 mutations are still more common than BRCA1 mutations); and c) the South-Western area, with many Phoenician and Carthaginian locations (where BRCA1 mutations are prevalent). We also found that phenotypic features such as high tumor grading and lack of expression of estrogen/progesterone receptors together with age at diagnosis and presence of ovarian cancer in the family may be predictive for the presence of BRCA1-2 germline mutations.

The Roman high- and low-avoidance rat lines differ in the acquisition, maintenance, extinction, and reinstatement of intravenous cocaine self-administration.

The selective breeding of Roman high- (RHA) and low-avoidance (RLA) rats for, respectively, rapid vs extremely poor acquisition of avoidant behavior in a shuttlebox has produced two phenotypes that differ in temperament traits, in mesocortical/mesolimbic dopamine system function, and in the behavioral and neurochemical responses to the acute and repeated administration of psychostimulants and opiates. The phenotypic traits of the RHA line predict higher susceptibility, compared with RLA rats, to the reinforcing properties of addictive substances like cocaine. The present study was designed to compare the acquisition, maintenance, reinstatement of drug-seeking after long-term extinction, and reacquisition of intravenous cocaine self-administration (SA) behavior in the Roman lines. Compared with RLA rats, the rates of responding during cocaine SA acquisition were higher, extinction from cocaine SA was prolonged, and drug-induced reinstatement of cocaine-seeking behavior was more robust in RHA rats. Moreover, only RHA rats reacquired extinguished lever-pressing activity when a low reinforcing dose of cocaine was available. These findings are consistent with the view that subjects with genetically determined high responsiveness to the acute and chronic (ie, sensitizing) effects of psychostimulants, such as RHA rats, also display a higher propensity to self -administer cocaine. Further comparative studies in the Roman lines, using SA paradigms that distinguish mere drug-taking from the compulsive and uncontrolled drug use that characterizes addiction in humans, may eventually help to characterize the relationships among genotype, temperament traits, and neurobiological mechanisms involved in the individual vulnerability to cocaine addiction.