Action initiation and punishment learning differ from childhood to adolescence while reward learning remains stable

Theoretical and empirical accounts suggest that adolescence is associated with heightened reward learning and impulsivity. Experimental tasks and computational models that can dissociate reward learning from the tendency to initiate actions impulsively (action initiation bias) are thus critical to characterise the mechanisms that drive developmental differences. However, existing work has rarely quantified both learning ability and action initiation, or it has relied on small samples. Here, using computational modelling of a learning task collected from a large sample (N = 742, 9-18 years, 11 countries), we test differences in reward and punishment learning and action initiation from childhood to adolescence. Computational modelling reveals that whilst punishment learning rates increase with age, reward learning remains stable. In parallel, action initiation biases decrease with age. Results are similar when considering pubertal stage instead of chronological age. We conclude that heightened reward responsivity in adolescence can reflect differences in action initiation rather than enhanced reward learning.

Psychosis and substance abuse increase the COVID-19 mortality risk

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has been a global challenge. High mortality rates have been reported in some risk groups, including patients with pre-existing mental disorders.

METHODS

We used electronic health records to retrospectively identify people infected due to COVID-19 (between March 2020 and March 2021) in the three territories of the Basque Country. COVID-19 cases were defined as individuals who had tested positive on a reverse transcription-polymerase chain reaction (PCR) test. Univariate and multivariate logistic regression models and multilevel analyses with generalized estimated equations were used to determine factors associated with COVID-19-related mortality and hospital admission.

RESULTS

The COVID-19 mortality rate was increased for patients with psychotic disorders [odds ratio (OR) adjusted: 1.45, 95% confidence interval (CI) (1.09-1.94), p = 0.0114] and patients with substance abuse [OR adjusted: 1.88, 95% CI (1.13-3.14, p < 0.0152)]. The mortality rate was lower for patients with affective disorders [OR adjusted: 0.80, 95% CI (0.61-0.99), p = 0.0407]. Hospital admission rates due to COVID-19 were higher in psychosis [OR adjusted: 2.90, 95% CI (2.36-3.56), p < 0.0001] and anxiety disorder groups [OR adjusted: 1.54, 95% CI (1.37-1.72), p < 0.0001]. Among admitted patients, COVID-19 mortality rate was decreased for those with affective disorders rate [OR adjusted: 0.72, 95% CI (0.55-0.95), p = 0.0194].

CONCLUSIONS

COVID-19-related mortality and hospitalizations rates were higher for patients with a pre-existing psychotic disorder.

Sex differences in psychiatric comorbidity and clinical presentation in youths with conduct disorder

BACKGROUND

Conduct disorder (CD) rarely occurs alone but is typically accompanied by comorbid psychiatric disorders, which complicates the clinical presentation and treatment of affected youths. The aim of this study was to investigate sex differences in comorbidity pattern in CD and to systematically explore the 'gender paradox' and 'delayed-onset pathway' hypotheses of female CD.

METHODS

As part of the FemNAT-CD multisite study, semistructured clinical interviews and rating scales were used to perform a comprehensive phenotypic characterization of 454 girls and 295 boys with CD (9-18 years), compared to 864 sex- and age-matched typically developing controls.

RESULTS

Girls with CD exhibited higher rates of current major depression, anxiety disorders, post-traumatic stress disorder and borderline personality disorder, whereas boys with CD had higher rates of current attention-deficit/hyperactivity disorder. In line with the 'gender paradox' hypothesis, relative to boys, girls with CD showed significantly more lifetime psychiatric comorbidities (incl. Alcohol Use Disorder), which were accompanied by more severe CD symptoms. Female and male youths with CD also differed significantly in their CD symptom profiles and distribution of age-of-onset subtypes of CD (i.e. fewer girls with childhood-onset CD). In line with the 'delayed-onset pathway' hypothesis, girls with adolescent-onset CD showed similar levels of dimensional psychopathology like boys with childhood-onset CD, while boys with adolescent-onset CD had the lowest levels of internalizing psychopathology.

CONCLUSIONS

Within the largest study of CD in girls performed to date, we found compelling evidence for sex differences in comorbidity patterns and clinical presentation of CD. Our findings further support aspects of the 'gender paradox' and 'delayed-onset pathway' hypotheses by showing that girls with CD had higher rates of comorbid lifetime mental disorders and functional impairments, and they usually developed CD during adolescence. These novel data on sex-specific clinical profiles of CD will be critical in informing intervention and prevention programmes.

The methylome in females with adolescent Conduct Disorder: Neural pathomechanisms and environmental risk factors

Conduct Disorder (CD) is an impairing psychiatric disorder of childhood and adolescence characterized by aggressive and dissocial behavior. Environmental factors such as maternal smoking during pregnancy, socio-economic status, trauma, or early life stress are associated with CD. Although the number of females with CD is rising in Western societies, CD is under-researched in female cohorts. We aimed at exploring the epigenetic signature of females with CD and its relation to psychosocial and environmental risk factors. We performed HpaII sensitive genome-wide methylation sequencing of 49 CD girls and 50 matched typically developing controls and linear regression models to identify differentially methylated CpG loci (tags) and regions. Significant tags and regions were mapped to the respective genes and tested for enrichment in pathways and brain developmental processes. Finally, epigenetic signatures were tested as mediators for CD-associated risk factors. We identified a 12% increased methylation 5’ of the neurite modulator SLITRK5 (FDR = 0.0046) in cases within a glucocorticoid receptor binding site. Functionally, methylation positively correlated with gene expression in lymphoblastoid cell lines. At systems-level, genes (uncorr. P < 0.01) were associated with development of neurons, neurite outgrowth or neuronal developmental processes. At gene expression level, the associated gene-networks are activated perinatally and during early childhood in neocortical regions, thalamus and striatum, and expressed in amygdala and hippocampus. Specifically, the epigenetic signatures of the gene network activated in the thalamus during early childhood correlated with the effect of parental education on CD status possibly mediating its protective effect. The differential methylation patterns identified in females with CD are likely to affect genes that are expressed in brain regions previously indicated in CD. We provide suggestive evidence that protective effects are likely mediated by epigenetic mechanisms impairing specific brain developmental networks and therefore exerting a long-term effect on neural functions in CD. Our results are exploratory and thus, further replication is needed.

Sex-specific associations of basal steroid hormones and neuropeptides with Conduct Disorder and neuroendocrine mediation of environmental risk

Conduct Disorder (CD) is characterized by severe aggressive and antisocial behavior. The stress hormone system has frequently been investigated as a neurobiological correlate of CD, while other interacting neuroendocrine biomarkers of sex hormone or neuropeptide systems have rarely been studied, especially in females. We examined multiple basal neuroendocrine biomarkers in female and male adolescents with CD compared to healthy controls (HCs), and explored whether they mediate effects of environmental risk factors on CD. Within the FemNAT-CD study, salivary cortisol, alpha-amylase, testosterone, dehydroepiandrosterone-sulfate (DHEA-S), estradiol, progesterone, oxytocin, and arginine-vasopressin were measured under basal conditions in 166 pubertal adolescents with CD, and 194 sex-, age-, and puberty-matched HCs (60% females, 9-18 years). Further, environmental risk factors were assessed. Single hormone analyses showed higher DHEA-S, and lower estradiol and progesterone levels in both females and males with CD relative to HCs. When accounting for interactions between neuroendocrine systems, a male-specific sex hormone factor (testosterone/DHEA-S) predicted male CD, while estradiol and a stress-system factor (cortisol/alpha-amylase) interacting with oxytocin predicted female CD. Estradiol, progesterone, and oxytocin partly explained associations between early environmental risk and CD. Findings provide evidence for sex-specific associations between basal neuroendocrine measures and CD. Especially altered sex hormones (androgen increases in males, estrogen reductions in females) robustly related to CD, while basal stress-system measures did not. Early environmental risk factors for CD may act partly through their effects on the neuroendocrine system, especially in females. Limitations (e.g., basal neuroendocrine assessment, different sample sizes per sex, pubertal participants, exploratory mediation analyses) are discussed.

DNA methylation signatures of aggression and closely related constructs: A meta-analysis of epigenome-wide studies across the lifespan

DNA methylation profiles of aggressive behavior may capture lifetime cumulative effects of genetic, stochastic, and environmental influences associated with aggression. Here, we report the first large meta-analysis of epigenome-wide association studies (EWAS) of aggressive behavior (N = 15,324 participants). In peripheral blood samples of 14,434 participants from 18 cohorts with mean ages ranging from 7 to 68 years, 13 methylation sites were significantly associated with aggression (alpha = 1.2 × 10-7; Bonferroni correction). In cord blood samples of 2425 children from five cohorts with aggression assessed at mean ages ranging from 4 to 7 years, 83% of these sites showed the same direction of association with childhood aggression (r = 0.74, p = 0.006) but no epigenome-wide significant sites were found. Top-sites (48 at a false discovery rate of 5% in the peripheral blood meta-analysis or in a combined meta-analysis of peripheral blood and cord blood) have been associated with chemical exposures, smoking, cognition, metabolic traits, and genetic variation (mQTLs). Three genes whose expression levels were associated with top-sites were previously linked to schizophrenia and general risk tolerance. At six CpGs, DNA methylation variation in blood mirrors variation in the brain. On average 44% (range = 3-82%) of the aggression-methylation association was explained by current and former smoking and BMI. These findings point at loci that are sensitive to chemical exposures with potential implications for neuronal functions. We hope these results to be a starting point for studies leading to applications as peripheral biomarkers and to reveal causal relationships with aggression and related traits.

Annual Research Review: Prevention of psychosis in adolescents - systematic review and meta-analysis of advances in detection, prognosis and intervention

BACKGROUND

The clinical high-risk state for psychosis (CHR-P) paradigm has facilitated the implementation of psychosis prevention into clinical practice; however, advancements in adolescent CHR-P populations are less established.

METHODS

We performed a PRISMA/MOOSE-compliant systematic review of the Web of Science database, from inception until 7 October 2019, to identify original studies conducted in CHR-P children and adolescents (mean age <18 years). Findings were systematically appraised around core themes: detection, prognosis and intervention. We performed meta-analyses (employing Q statistics and I ² test) regarding the proportion of CHR-P subgroups, the prevalence of baseline comorbid mental disorders, the risk of psychosis onset and the type of interventions received at baseline. Quality assessment and publication bias were also analysed.

RESULTS

Eighty-seven articles were included (n = 4,667 CHR-P individuals). Quality of studies ranged from 3.5 to 8 (median 5.5) on a modified Newcastle-Ottawa scale. Detection: Individuals were aged 15.6 ± 1.2 years (51.5% males), mostly (83%) presenting with attenuated positive psychotic symptoms. CHR-P psychometric accuracy improved when caregivers served as additional informants. Comorbid mood (46.4%) and anxiety (31.4%) disorders were highly prevalent. Functioning and cognition were impaired. Neurobiological studies were inconclusive.

PROGNOSIS

Risk for psychosis was 10.4% (95%CI: 5.8%-18.1%) at 6 months, 20% (95%CI: 15%-26%) at 12 months, 23% (95%CI: 18%-29%) at 24 months and 23.3% (95%CI: 17.3%-30.7%) at ≥36 months.

INTERVENTIONS

There was not enough evidence to recommend one specific treatment (including cognitive behavioural therapy) over the others (including control conditions) to prevent the transition to psychosis in this population. Randomised controlled trials suggested that family interventions, cognitive remediation and fish oil supplementation may improve cognition, symptoms and functioning. At baseline, 30% of CHR-P adolescents were prescribed antipsychotics and 60% received psychotherapy.

CONCLUSIONS

It is possible to detect and formulate a group-level prognosis in adolescents at risk for psychosis. Future interventional research is required.

Architecture, urban planning and collective identity: Bilbao as a case study

The emergence of a collective identity, a complex social and psychological process, may be linked to a specific place and a particular urban layout. Architecture demarcates interior and exterior spaces that not only frame our relationships but can also generate a mirror image of the internal world. The authors examine relevant contributions from the sparse psychoanalytic literature on this subject, to support their hypothesis that changes to a city's landscape, design, or architecture, when wholeheartedly embraced by its citizens, can serve to forge a new collective identity that helps to deal with absence, pain, and loss. They present the city of Bilbao, Spain, as a case study. This once thriving industrial city had collapsed into economic ruin, rife with social conflict, but since the 1990s, in an urban renewal, has emerged as a unique tourist destination. It has become a modern art and cultural center, symbolized by its most famous piece of contemporary architecture.

Investigating Sex Differences in Emotion Recognition, Learning, and Regulation Among Youths With Conduct Disorder

OBJECTIVE

Conduct disorder (CD) is a serious neurodevelopmental disorder marked by notably higher prevalence rates for boys than girls. Converging evidence suggests that CD is associated with impairments in emotion recognition, learning, and regulation. However, it is not known whether there are sex differences in the relationship between CD and emotion dysfunction. Prior studies on emotion functioning in CD have so far been underpowered for investigating sex differences. Therefore, our primary aim was to characterize emotion processing skills in a large sample of girls and boys with CD compared to typically developing controls (TDCs) using a comprehensive neuropsychological test battery.

METHOD

We included 542 youths with CD (317 girls) and 710 TDCs (479 girls), 9 to 18 years of age, from a European multisite study (FemNAT-CD). Participants completed three experimental tasks assessing emotion recognition, learning, and regulation, respectively. Data were analyzed to test for effects of group and sex, and group-by-sex interactions, while controlling for potentially confounding factors.

RESULTS

Relative to TDCs, youths with CD showed impaired emotion recognition (that was related to more physical and proactive aggression, and higher CU traits), emotional learning (specifically from punishment), and emotion regulation. Boys and girls with CD, however, displayed similar impairments in emotion processing.

CONCLUSION

This study provides compelling evidence for a relationship between CD and deficient neurocognitive functioning across three emotional domains that have previously been linked to CD etiology. However, there was no support for sex-specific profiles of emotion dysfunction, suggesting that current neurocognitive models of CD apply equally to both sexes.

Neuropsychological Subgroups of Emotion Processing in Youths With Conduct Disorder

Background: At the group level, youths with conduct disorder (CD) show deficient emotion processing across various tasks compared to typically developing controls (TDC). But little is known about neuropsychological subgroups within the CD population, the clinical correlates of emotion processing deficits [for instance, with regard to the presence or absence of the DSM-5 Limited Prosocial Emotions (LPE) specifier], and associated risk factors. Methods: 542 children and adolescents with CD (317 girls) and 710 TDCs (479 girls), aged 9-18 years, were included from the FemNAT-CD multisite study. All participants completed three neuropsychological tasks assessing emotion recognition, emotion learning, and emotion regulation. We used a self-report measure of callous-unemotional traits to create a proxy for the LPE specifier. Results: Relative to TDCs, youths with CD as a group performed worse in all three emotion domains. But using clinically based cut-off scores, we found poor emotion recognition skills in only 23% of the participants with CD, followed by emotion regulation deficits in 18%, and emotion learning deficits in 13% of the CD group. Critically, the majority of youths with CD (~56%) did not demonstrate any meaningful neuropsychological deficit, and only a very small proportion showed pervasive deficits across all three domains (~1%). Further analyses indicate that established DSM-5 subtypes of CD are not tightly linked to neurocognitive deficits in one particular emotion domain over another (i.e., emotion recognition deficits in CD+LPE vs. emotion regulation deficits in CD-LPE). Conclusions: Findings from this large-scale data set suggest substantial neuropsychological diversity in emotion processing in the CD population and, consequently, only a subgroup of youths with CD are likely to benefit from additional behavioral interventions specifically targeting emotion processing mechanisms.

Community Violence Exposure and Conduct Problems in Children and Adolescents with Conduct Disorder and Healthy Controls

Exposure to community violence through witnessing or being directly victimized has been associated with conduct problems in a range of studies. However, the relationship between community violence exposure (CVE) and conduct problems has never been studied separately in healthy individuals and individuals with conduct disorder (CD). Therefore, it is not clear whether the association between CVE and conduct problems is due to confounding factors, because those with high conduct problems also tend to live in more violent neighborhoods, i.e., an ecological fallacy. Hence, the aim of the present study was: (1) to investigate whether the association between recent CVE and current conduct problems holds true for healthy controls as well as adolescents with a diagnosis of CD; (2) to examine whether the association is stable in both groups when including effects of aggression subtypes (proactive/reactive aggression), age, gender, site and socioeconomic status (SES); and (3) to test whether proactive or reactive aggression mediate the link between CVE and conduct problems. Data from 1178 children and adolescents (62% female; 44% CD) aged between 9 years and 18 years from seven European countries were analyzed. Conduct problems were assessed using the Kiddie-Schedule of Affective Disorders and Schizophrenia diagnostic interview. Information about CVE and aggression subtypes was obtained using self-report questionnaires (Social and Health Assessment and Reactive-Proactive aggression Questionnaire (RPQ), respectively). The association between witnessing community violence and conduct problems was significant in both groups (adolescents with CD and healthy controls). The association was also stable after examining the mediating effects of aggression subtypes while including moderating effects of age, gender and SES and controlling for effects of site in both groups. There were no clear differences between the groups in the strength of the association between witnessing violence and conduct problems. However, we found evidence for a ceiling effect, i.e., individuals with very high levels of conduct problems could not show a further increase if exposed to CVE and vice versa. Results indicate that there was no evidence for an ecological fallacy being the primary cause of the association, i.e., CVE must be considered a valid risk factor in the etiology of CD.

Stigma and discrimination towards people with schizophrenia and their family members. A qualitative study with focus groups

BACKGROUND

There is a scarcity of data regarding the actual stigma and discrimination experienced by schizophrenic patients and their relatives. Those experiences can vary significantly depending on the specific social group involved. We have explored such phenomena in our culture with a qualitative technique.

METHODS

We developed a qualitative study with focus groups of clinically stable schizophrenic outpatients (N = 18) and relatives (N = 26). Three groups were performed in each sample.

RESULTS

Six categories of stigma and discrimination experiences were extracted from the patients' data: Mental illness vs. Lack of will, Prejudice related to dangerousness, Over-protection-infantilization, Daily social discrimination, Discrimination in health care, Descendants, Avoidance-social isolation. Data from relatives were divided into three sets: discrimination towards the patients witnessed by relatives, discrimination suffered by the relatives themselves and discrimination exerted by the relatives on the patients.

CONCLUSIONS

Patients and relatives describe a great variety of stigma and discrimination experiences in all areas of life, including health care. Isolation and avoidance are common reactions to those experiences. Publicizing these stigma and discrimination experiences could help to reduce stigmatizing attitudes in society and result in healthier reactions from patients, favoring a better course of the illness.

Abnormal renal vascular reactivity to acetylcholine and nitroprusside in aging rats

1. The actions of acetylcholine (ACh), CaCl2 and nitroprusside (NP) were studied in aortic strips and in the perfused kidneys from adult (4-6 months old) and aging (23-24 months old) rats. 2. ACh and CaCl2 produced a dose-related relaxation in aortic strips from adult and old rats; maximal responses to both vasodilators were significantly reduced (ACh: adult = 66.4 +/- 6.1%, Old = 27.1 +/- 5.7%, P < 0.001; CaCl2: adult = 75.6 +/- 3.9%, Old = 54.1 +/- 4.1%, P < 0.01) in aortas from old rats. NP-evoked relaxation was not significantly different between the two groups. 3. In kidneys from adult rats, ACh produced dose-related decreases in renal perfusion pressure (RPP), whereas, in kidneys from old rats, ACh produced a dose-related decrease at low doses, and biphasic responses (vasodilatation followed by vasoconstriction) at medium to high doses, with a reduced vasodilator component. Vasodilator response to ACh to the highest dose; ACh; adult = 78.7 +/- 2.8%, Old = 40.6 +/- 2.6%, P < 0.001). In kidneys from adult rats, NP produced a dose-related decrease in RPP. However, in kidneys from old rats, NP produced vasoconstriction at low doses, biphasic responses at medium doses (vasoconstriction followed by vasodilation), and vasodilation at the highest dose. 4. The results of the present study demonstrated that: (a) The isolated perfused kidney from aging rats had a dual response (with an important vasoconstrictor component) to ACh and NP, which may be due to the release of a nonprostanoid vasoconstrictor or to abnormalities in the renal vascular smooth muscle. In contrast, in aortic-strips from old and adult rats, these agents only caused relaxation; (b) aging is accompanied by reduced endothelium-dependent relaxation both in large arteries and in resistance vessels; and (c) large arteries from aging rats require a higher concentration of extracellular calcium to stabilize the membrane of smooth muscle cells.

Vascular reactivity and flow-pressure curve in isolated kidneys from rats with N-nitro-L-arginine methyl ester-induced hypertension

OBJECTIVES

The purpose of this study was to determine the contribution of the functional changes in resistance vessels to the hypertension induced by chronic nitric oxide synthase inhibition in rats. Another goal of this study was to evaluate whether this model of hypertension is accompanied by changes in the activity of endothelium-derived hyperpolarizing factor (EDHF).

METHODS

Hypertension was induced by long-term (6 weeks) oral administration of N-nitro-L-arginine methyl ester (L-NAME; 75 mg/100 ml in the drinking fluid). Vascular reactivity to vasoconstrictors (phenylephrine and barium chloride) and vasodilators (acetylcholine and nitroprusside) and the flow-pressure curve were examined in isolated perfused kidneys preparations. Vascular reactivity to vasoconstrictors and the flow-pressure curve were studied under basal conditions or after the infusion of L-arginine (100 mumol/l). The activity of EDHF was evaluated by comparing the dose-response curves for acetylcholine obtained in potassium chloride- and phenylephrine-preconstricted preparations.

RESULTS

Kidneys from L-NAME-induced hypertensive rats showed increased sensitivity to vasoconstrictors with a greater duration of the pressor responses at high doses and markedly up-shifted flow-pressure curve in comparison with that obtained in control kidneys. These differences disappeared when the kidneys from control and L-NAME-treated rats were infused with L-arginine. The kidneys from L-NAME-treated rats also showed a decreased responsiveness to acetylcholine with an augmented reactivity to nitroprusside. The acetylcholine dose-response curve was reduced in control preparations and greatly attenuated in L-NAME-treated preparations when the renal vasculature was preconstricted with potassium chloride.

CONCLUSIONS

The changes in vascular reactivity observed in L-NAME-induced hypertensive rats may play an important role in the pathogenesis of this type of hypertension. Moreover, it is also suggested that long-term nitric oxide inhibition may be associated with increased activity of EDHF.

Endothelium-dependent and endothelium-independent vasodilation in hyperthyroid and hypothyroid rats

The effects of hyper- and hypothyroidism on the vasorelaxing responses to acetylcholine (ACh), sodium nitroprusside (NP), and CaCl2 were investigated in aortic strips and isolated perfused kidneys. The renal vascular reactivity to ACh and NP was increased in hyperthyroid rats, whereas the concentration-response curve to ACh in hypothyroid rats was flattened. In the renal vasculature from hypothyroid rats, NP produced a dual response: vasoconstriction at low doses and vasodilation at medium to high doses. Aortic strips from hyperthyroid rats showed an increased response to ACh without significant differences between hypothyroid and control groups. Aortic strips from all three experimental groups showed a similar relaxing response to CaCl2. These results indicate that: (1) the raised arterial pressure of hyperthyroid rats is not associated with a reduced endothelium-dependent and calcium-induced vasodilation, and (2) the changes in responsiveness to vasodilators in resistance vessels from hyper- and hypothyroid rats may play a role in the increased and decreased peripheral vascular resistances, respectively, previously reported in such animals.

Effects of chronic increased salt intake on nitric oxide synthesis inhibition-induced hypertension

OBJECTIVE AND METHOD

Experimental evidence suggests that endogenous nitric oxide plays an important role in the homeostatic response to an increase in sodium intake. In the present study we evaluated the influence of a high sodium intake (1% NaCl as drinking water) on arterial hypertension induced by long-term (6-7 weeks) inhibition of nitric oxide synthesis [NG-nitro-L-arginine methyl ester (L-NAME), 75 mg/100 ml in the drinking fluid] in rats.

RESULTS

Treatment with L-NAME induced progressive elevations in tail-cuff systolic blood pressure, but there were no differences between rats drinking tap water and rats drinking 1% NaCl. Direct measurement of blood pressure at the end of the treatment confirmed the hypertension and the lack of differences between the two groups treated with L-NAME. Metabolic studies performed at the end of L-NAME treatment showed a reduced glomerular filtration rate and elevated urinary excretion of immunoreactive endothelin in the two hypertensive groups treated with L-NAME. Drinking intake, diuresis and natriuresis were significantly higher only in the L-NAME group drinking 1% NaCl. Both groups treated with L-NAME showed an accelerated and increased diuretic and natriuretic response to an isotonic 0.9% NaCl load (2.5 ml/100 g body weight, intraperitoneally). At the end of the study ventricular hypertrophy was observed in both L-NAME groups.

CONCLUSION

The present results indicate that the time-dependent elevation in blood pressure produced by long-term inhibition of nitric oxide production is not affected by an increased sodium intake. However, salt supplementation induced the development of a polyuria and polydipsia syndrome in rats treated with L-NAME. The elevated excretion of endothelin in both groups treated with L-NAME suggests the possible participation of endothelin in the development of L-NAME hypertension.