41 research outputs found
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Distinct Contributions of Median Raphe Nucleus to Contextual Fear Conditioning and Fear-Potentiated Startle
Ascending 5-HT projections from the
median raphe nucleus (MRN), probably to the
hippocampus, are implicated in the acquisition
of contextual fear (background stimuli), as
assessed by freezing behavior. Foreground cues
like light, used as a conditioned stimulus (CS) in
classical fear conditioning, also cause freezing
through thalamic transmission to the amygdala.
As the MRN projects to the hippocampus and
amygdala, the role of this raphe nucleus in fear
conditioning to explicit cues remains to be
explained. Here we analyzed the behavior of
rats with MRN electrolytic lesions in a
contextual conditioning situation and in a fear-potentiated
startle procedure. The animals
received MRN electrolytic lesions either before
or on the day after two consecutive training
sessions in which they were submitted to 10
conditioning trials, each in an experimental
chamber (same context) where they. received
foot-shocks (0.6 mA, 1 sec) paired to a 4-sec
light CS. Seven to ten days later, the animals
were submitted to testing sessions for assessing
conditioned fear when they were placed for five
shocks, and the duration of contextual freezing
was recorded. The animals were then submitted
to a fear-potentiated startle in response to a 4-sec
light-CS, followed by white noise (100 dB, 50 ms). Control rats (sham) tested in the same
context showed more freezing than did rats
with pre- or post-training MRN lesions. Startle
was clearly potentiated in the presence of light CS in the sham-lesioned animals. Whereas pretraining
lesions reduced both freezing and fear-potentiated
startle, the post-training lesions
reduced only freezing to context, without
changing the fear-potentiated startle. In a
second experiment, neurotoxic lesions of the
MRN with local injections of N-methyl-D-aspartate
or the activation of 5-HT1A somatodendritic
auto-receptors of the MRN by
microinjections of the 5-HT1A receptor agonist
8-hydroxy- 2-(di-n-propylamino)tetralin (8-OH-DPAT)
before the training sessions also reduced
the amount of freezing and the fear-potentiated
startle. Freezing is a prominent response of
contextual fear conditioning, but does not seem
to be crucial for the enhancement of the startle
reflex by explicit aversive cues. As fear-potentiated
startle may be produced in posttraining
lesioned rats that are unable to freeze
to fear contextual stimuli, dissociable systems
seem to be recruited in each condition. Thus,
contextual fear and fear-potentiated startle are
conveyed by distinct 5-HT-mediated circuits of
the MRN
\u3ci\u3eIn Situ\u3c/i\u3e Cardiac Performance of Pacific Bluefin Tuna Hearts in Response to Acute Temperature Change
This study reports the cardiovascular physiology of the Pacific bluefin tuna (Thunnus orientalis) in an in situ heart preparation. The performance of the Pacific bluefin tuna heart was examined at temperatures from 30°C down to 2°C. Heart rates ranged from 156 beats min–1 at 30°C to 13 beats min–1 at 2°C. Maximal stroke volumes were 1.1 ml kg–1 at 25°C and 1.3 ml kg–1 at 2°C. Maximal cardiac outputs were 18.1 ml kg–1 min–1 at 2°C and 106 ml kg–1 min–1 at 25°C. These data indicate that cardiovascular function in the Pacific bluefin tuna exhibits a strong temperature dependence, but cardiac function is retained at temperatures colder than those tolerated by tropical tunas. The Pacific bluefin tuna\u27s cardiac performance in the cold may be a key adaptation supporting the broad thermal niche of the bluefin tuna group in the wild. In situ data from Pacific bluefin are compared to in situ measurements of cardiac performance in yellowfin tuna and preliminary results from albacore tuna
Concentrações plasmáticas de corticosterone em ratos Carioca Alto- e Carioca Bajo-Congelamento condicionado após uma tarefa de medo condicionado
Our group in the Psychology Department at Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio) developed a rat genetic model of extreme freezing in response to contextual cues in an experimental chamber previously associated with footshock. One of the lines, Carioca High Freezing (CHF), exhibits an enhanced conditioned freezing response, whereas the other line, Carioca Low Freezing (CLF), shows the opposite response. The present study investigated corticosterone concentration between these two lines of animals and a random (RND) line of rats both under basal conditions and test condition after an emotional challenge using a contextual fear conditioning protocol. Comparisons between basal and test plasma corticosterone concentrations suggested differential basal and fear-induced differences between the two lines. The differences between basal conditions is an important and relevant aspect to be considered in behavioral experiments using or assessing stress and could help to understand variability in naïve populations.Casi toda la investigación farmacológica en estrés y desórdenes de ansiedad es realizada generalmente en poblaciones de animales que se supone son comparables. En el laboratorio de Neurociencia Comportamental de la Pontificia Universidad Católica de Río de Janeiro (Brasil), dos nuevas líneas de ratas Wistar fueron aisladas por la selección fenotípica de la respuesta emocional en el protocolo de condicionamiento de la respuesta de miedo. Una de las líneas, denominada Carioca High Freezing (CHF) muestra una respuesta aumentada de congelamiento en el test, mientras que la otra –Carioca Low Freezing (CLF)– muestra la respuesta opuesta. Aquí presentamos datos orientados a evaluar las condiciones basales y la vulnerabilidad al estrés entre las dos líneas. Los niveles de corticosterona fueron comparados entre las dos líneas tanto en condiciones basales como después de un desafío emocional utilizando el protocolo de miedo condicionado. La comparación entre las concentraciones plasmáticas de corticosterona basal y luego del retest sugiere diferencias basales y diferencias inducidas por el miedo entre las dos líneas. Las diferencias en las condiciones basales es un aspecto importante y relevante que debe ser considerado en experimentos comportamentales que usen o evalúen el estrés y podría ayudar a comprender la variabilidad encontrada en las poblaciones.Nosso grupo no Departamento de Psicologia da Universidade Católica do Rio de Janeiro desenvolveu um modelo genético com ratos que apresentam respostas extremas de congelamento a estímulos contextuais de uma caixa experimental previamente associados a choques elétricos. Uma das linhagens, Carioca High Freezing (CHF) apresenta uma resposta aumentada de congelamento condicionado. A outra linhagem, Carioca Low Freezing (CLF) apresenta a resposta de congelamento condicionada em direção oposta. O presente trabalho comparou os níveis de corticosterona entre as duas linhagens assim como uma terceira linhagem com cruzamento aleatório (RND) tanto em condições basais assim como em um teste onde os animais foram expostos á situação de condicionamento contextual de medo. A comparação entre as concentrações plasmáticas de corticosterona basal e depois do teste sugere diferenças basais assim como diferenças induzidas pelo medo condicionado entre as duas linhagens. As diferenças nas condições basais é um aspecto importante e relevante que deve ser levado em consideração em experimentos que avaliem o estresse e pode ajudar na compreensão da variabilidade nas populações
Measuring social norms and attitudes about age-disparate transactional sex: Psychometric testing of the NAATSS
Background: Transactional sex between girls under 18 years-old and adult men at least ten years older, known as age-disparate transactional sex (ADTS), is an established risk factor for HIV, STI and early pregnancy among girls and women. Social norms or beliefs about what others expect from you and what others do can sustain behaviours such as ADTS even when individuals may be personally against them. In order to evaluate interventions to change social norms, validated instruments for measuring change in personal beliefs and social norms regarding ADTS are needed. Methods: Items for the Norms and Attitudes on Age-Disparate Transactional Sex Scale (NAATSS) were generated based on qualitative interviews and expert panel review. The reliability and validity of the NAATSS was tested in a representative sample (N = 431) from Brazilian favelas. Factor analysis assessed construct validity, Cronbach's alpha assessed reliability, and t-tests and analysis of variances tested hypothesized differences between gender, age, and previous experience with ADTS in both the social norms and personal beliefs domains. Findings: Factor analysis revealed three factors in each domain. The factors were labelled “Attributions to Girls’ Behaviour” which has 5 items, “Men's Motivations” with 5 items, and “Girls’ Readiness to have Sex” with 3 items. The subscales evidenced acceptable reliability with Cronbach's alphas ranging from 0.72 to 0.83 for the social norms subscales and 0.59 to 0.82 for the personal beliefs subscales. Interpretation: The items were developed based on qualitative research and expert rankings and the resulting Norms and Attitudes on ADTS Scale exhibits strong psychometric properties. Each of the three subscales within the two domains illustrate good factor structure, acceptable internal consistency reliability, and are supported by the significance of the hypothesized group differences. Funding: This work was supported by the OAK Foundation [grant number OCAY-16-188]
Altered Eigenvector Centrality is Related to Local Resting-State Network Functional Connectivity in Patients with Longstanding Type 1 Diabetes Mellitus
Introduction: Longstanding type 1 diabetes (T1DM) is associated with microangiopathy
and poorer cognition. In the brain, T1DM is related to increased functional resting-state
network (RSN) connectivity in patients without, which was decreased in patients with
clinically evident microangiopathy. Subcortical structure seems affected in both patient
groups. How these localized alterations affect the hierarchy of the functional network in
T1DM is unknown. Eigenvector centrality mapping (ECM) and degree centrality are
graph theoretical methods that allow determining the relative importance (ECM) and
connectedness (degree centrality) of regions within the whole-brain network hierarchy.
Methods: Therefore, ECM and degree centrality of resting-state functional MRI-scans
was compared between 51 patients with, 53 patients without proliferative retinopathy,
and 49 controls, and associated with RSN connectivity, subcortical gray matter volume,
and cognition.
Results: In all patients versus controls, ECM and degree centrality were lower in the
bilateral thalamus and the dorsal striatum, with lowest values in patients without
proliferative retinopathy (PFWE<0.05). Increased ECM in this group versus patients with
proliferative retinopathy was seen in the bilateral lateral occipital cortex, and in the right
lateral cortex versus controls (PFWE<0.05). In all patients, ECM and degree centrality
were related to altered visual, sensorimotor, and auditory and language RSN connectivity
(PFWE0.05).
Conclusion: Our findings suggest reorganization of the hierarchy of the cortical
connectivity network in patients without proliferative retinopathy, which is lost with
disease progression. Centrality seems sensitive to capture early T1DM-related functional
connectivity alterations, but not disease progression