Effects of environmental and physiological covariates on sex differences in unconditioned and conditioned anxiety and fear in a large sample of genetically heterogeneous (N/Nih-HS) rats

Physiological and environmental variables, or covariates, can account for an important portion of the variability observed in behavioural/physiological results from different laboratories even when using the same type of animals and phenotyping procedures. We present the results of a behavioural study with a sample of 1456 genetically heterogeneous N/Nih-HS rats, including males and females, which are part of a larger genome-wide fine-mapping QTL (Quantitative Trait Loci) study. N/Nih-HS rats have been derived from 8 inbred strains and provide very small distance between genetic recombinations, which makes them a unique tool for fine-mapping QTL studies. The behavioural test battery comprised the elevated zero-maze test for anxiety, novel-cage (open-field like) activity, two-way active avoidance acquisition (related to conditioned anxiety) and context-conditioned freezing (i.e. classically conditioned fear). Using factorial analyses of variance (ANOVAs) we aimed to analyse sex differences in anxiety and fear in this N/Nih-HS rat sample, as well as to assess the effects of (and interactions with) other independent factors, such as batch, season, coat colour and experimenter. Body weight was taken as a quantitative covariate and analysed by covariance analysis (ANCOVA). Obliquely-rotated factor analyses were also performed separately for each sex, in order to evaluate associations among the most relevant variables from each behavioural test and the common dimensions (i.e. factors) underlying the different behavioural responses. ANOVA analyses showed a consistent pattern of sex effects, with females showing less signs of anxiety and fear than males across all tests. There were also significant main effects of batch, season, colour and experimenter on almost all behavioural variables, as well as "sex × batch", "sex × season" and "sex × experimenter" interactions. Body weight showed significant effects in the ANCOVAs of most behavioural measures, but sex effects were still present in spite of (and after controlling for) these "body weight" effects. Factor analyses of relevant variables from each test showed a two-fold factor structure in both sexes, with the first factor mainly representing anxiety and conditioned fear in males, while in females the first factor was dominated by loadings of activity measures. Thus, besides showing consistent sex differences in anxiety-, fear- and activity-related responses in N/Nih-HS rats, the present study shows that females' behaviour is predominantly influenced by activity while males are more influenced by anxiety. Moreover, the results point out that, besides "sex" effects, physiological variables such as colour and body weight, and environmental factors as batch/season or "experimenter", have to be taken into account in both behavioural and quantitative genetic studies because of their demonstrated influences on phenotypic outcomes

The Roman high- and low- avoidance rat strains differ in fear-potentiated startle and classical aversive conditioning

The Swiss sublines of Roman High-(RHA/Verh) and Low-(RLA/Verh) Avoidance rats have been genetically selected (and outbred) since 1972 because of their good versus extremely poor acquisition of two-way, active avoidance. Inbred strains (RHA-I and RLA-I), derived from those two lines, have been maintained at our laboratory since 1997. The RLA line/strain shows increased stress-induced endocrine responses and enhanced anxiety/fearfulness in a variety of unconditioned behavioural variables and tests. Thus far, however, the Roman rat strains have not been compared in procedures involving classical fear conditioning to cues or contexts. Therefore, the present work was aimed at comparing RHA-I and RLA-I rats in 1) two different procedures of fear-potentiated startle and 2) in a classical fear conditioning (i.e., conditioned freezing) paradigm. The results indicate that, compared to RHA-I rats, RLA-I animals display higher levels of conditioned fear (as measured either by startle responses or freezing behavior) across those different tasksLas sublíneas suizas de ratas Romanas «High»-(RHA/Verh) y «Low»-(RLA/Verh) «Avoidance» han sido seleccionadas genéticamente, desde 1972, en función de su excelente (RHA) o extremadamente pobre adquisición de la tarea de evitación activa en dos sentidos. Cepas consanguíneas (RHA-I y RLA-I), derivadas de las dos líneas anteriores, se mantienen en nuestro laboratorio desde 1997. En comparación con la cepa RHA-I, la cepa RLA-I muestra incrementos en las respuestas hormonales al estrés, así como en conductas de ansiedad/miedo en una variedad de pruebas y variables conductuales incondicionadas. Hasta la fecha, las cepas de ratas Romanas no han sido comparadas en procedimientos de condicionamiento clásico de miedo a contextos o estímulos discretos. El presente trabajo tuvo como objetivo comparar ambas en 1) dos procedimientos de medida de la respuesta de sobresalto potenciada por miedo; y, 2) en un procedimiento de condicionamiento clásico de miedo (petrificación condicionada). Los resultados indican que las ratas RLA-I muestran niveles mayores de condicionamiento de miedo (respuesta de sobresalto y respuesta de petrificación) que las RHA-I, reforzando así los perfiles diferenciales de ansiedad/miedo de las dos cepa

High-resolution genome screen for bone mineral density in heterogeneous stock rat

We previously demonstrated that skeletal mass, structure, and biomechanical properties vary considerably in heterogeneous stock (HS) rat strains. In addition, we observed strong heritability for several of these skeletal phenotypes in the HS rat model, suggesting that it represents a unique genetic resource for dissecting the complex genetics underlying bone fragility. The purpose of this study was to identify and localize genes associated with bone mineral density in HS rats. We measured bone phenotypes from 1524 adult male and female HS rats between 17 and 20 weeks of age. Phenotypes included dual-energy X-ray absorptiometry (DXA) measurements for bone mineral content and areal bone mineral density (aBMD) for femur and lumbar spine (L3-L5), and volumetric BMD measurements by CT for the midshaft and distal femur, femur neck, and fifth lumbar vertebra (L5). A total of 70,000 polymorphic single-nucleotide polymorphisms (SNPs) distributed throughout the genome were selected from genotypes obtained from the Affymetrix rat custom SNPs array for the HS rat population. These SNPs spanned the HS rat genome with a mean linkage disequilibrium coefficient between neighboring SNPs of 0.95. Haplotypes were estimated across the entire genome for each rat using a multipoint haplotype reconstruction method, which calculates the probability of descent for each genotyped locus from each of the eight founder HS strains. The haplotypes were tested for association with each bone density phenotype via a mixed model with covariate adjustment. We identified quantitative trait loci (QTLs) for BMD phenotypes on chromosomes 2, 9, 10, and 13 meeting a conservative genomewide empiric significance threshold (false discovery rate [FDR] = 5%; p < 3 × 10(-6)). Importantly, most QTLs were localized to very small genomic regions (1-3 megabases [Mb]), allowing us to identify a narrow set of potential candidate genes including both novel genes and genes previously shown to have roles in skeletal development and homeostasis

The Roman High-and Low-Avoidance rat strains differ in fear-potentiated startle and classical aversive conditioning

The Swiss sublines of Roman High-(RHA/Verh) and Low-(RLA/Verh) Avoidance rats have been genetically selected (and outbred) since 1972 because of their good versus extremely poor acquisition of two-way, active avoidance. Inbred strains (RHA-I and RLA-I), derived from those two lines, have been maintained at our laboratory since 1997. The RLA line/strain shows increased stress-induced endocrine responses and enhanced anxiety/fearfulness in a variety of unconditioned behavioural variables and tests. Thus far, however, the Roman rat strains have not been compared in procedures involving classical fear conditioning to cues or contexts. Therefore, the present work was aimed at comparing RHA-I and RLA-I rats in 1) two different procedures of fear-potentiated startle and 2) in a classical fear conditioning (i.e., conditioned freezing) paradigm. The results indicate that, compared to RHA-I rats, RLA-I animals display higher levels of conditioned fear (as measured either by startle responses or freezing behavior) across those different tasksLas sublíneas suizas de ratas Romanas «High»-(RHA/Verh) y «Low»-(RLA/Verh) «Avoidance» han sido seleccionadas genéticamente, desde 1972, en función de su excelente (RHA) o extremadamente pobre adquisición de la tarea de evitación activa en dos sentidos. Cepas consanguíneas (RHA-I y RLA-I), derivadas de las dos líneas anteriores, se mantienen en nuestro laboratorio desde 1997. En comparación con la cepa RHA-I, la cepa RLA-I muestra incrementos en las respuestas hormonales al estrés, así como en conductas de ansiedad/miedo en una variedad de pruebas y variables conductuales incondicionadas. Hasta la fecha, las cepas de ratas Romanas no han sido comparadas en procedimientos de condicionamiento clásico de miedo a contextos o estímulos discretos. El presente trabajo tuvo como objetivo comparar ambas en 1) dos procedimientos de medida de la respuesta de sobresalto potenciada por miedo; y, 2) en un procedimiento de condicionamiento clásico de miedo (petrificación condicionada). Los resultados indican que las ratas RLA-I muestran niveles mayores de condicionamiento de miedo (respuesta de sobresalto y respuesta de petrificación) que las RHA-I, reforzando así los perfiles diferenciales de ansiedad/miedo de las dos cepas

Fine mapping of bone structure and strength QTLs in heterogeneous stock rat

We previously demonstrated that skeletal structure and strength phenotypes vary considerably in heterogeneous stock (HS) rats. These phenotypes were found to be strongly heritable, suggesting that the HS rat model represents a unique genetic resource for dissecting the complex genetic etiology underlying bone fragility. The purpose of this study was to identify and localize genes associated with bone structure and strength phenotypes using 1524 adult male and female HS rats between 17 to 20 weeks of age. Structure measures included femur length, neck width, head width; femur and lumbar spine (L3-5) areas obtained by DXA; and cross-sectional areas (CSA) at the midshaft, distal femur and femoral neck, and the 5th lumbar vertebra measured by CT. In addition, measures of strength of the whole femur and femoral neck were obtained. Approximately 70,000 polymorphic SNPs distributed throughout the rat genome were selected for genotyping, with a mean linkage disequilibrium coefficient between neighboring SNPs of 0.95. Haplotypes were estimated across the entire genome for each rat using a multipoint haplotype reconstruction method, which calculates the probability of descent at each locus from each of the 8 HS founder strains. The haplotypes were then tested for association with each structure and strength phenotype via a mixed model with covariate adjustment. We identified quantitative trait loci (QTLs) for structure phenotypes on chromosomes 3, 8, 10, 12, 17 and 20, and QTLs for strength phenotypes on chromosomes 5, 10 and 11 that met a conservative genome-wide empiric significance threshold (FDR=5%; P<3×10(-6)). Importantly, most QTLs were localized to very narrow genomic regions (as small as 0.3 Mb and up to 3 Mb), each harboring a small set of candidate genes, both novel and previously shown to have roles in skeletal development and homeostasis

Aplicabilidad del análisis de microarray en la detección de patrones de expresión genética diferencial en procesos psicológicos: expresión genética amigdalar en ratas N/Nih-HS extremas en ansiedad.

En el presente trabajo, se revisan las principales investigaciones sobre las bases gen&eacute;ticas del miedo, los trastornos de ansiedad y depresivos, as&iacute; como de la susceptibilidad a las drogas, que han utilizado la t&eacute;cnica de microarray. Finalmente se presenta un resumen de algunos resultados preliminares, obtenidos por nuestro grupo de investigaci&oacute;n, en el an&aacute;lisis de la expresi&oacute;n g&eacute;nica diferencial en ratas gen&eacute;ticamente heterog&eacute;neas (N/Nih-HS) seleccionadas por su alta/baja ansiedad, en funci&oacute;n de su capacidad para la adquisici&oacute;n de la tarea de evitaci&oacute;n activa en dos sentidos (en la Shuttle-box)

Ansiedad en ratas genéticamente heterogéneas : hacia la identificación de genes para caracteres conductuales cuantitativos

El uso de roedores genéticamente heterogéneos constituye una estrategia única para la identificación y el 'mapeo fino' a alta resolución de locus genéticos (QTL) con influencia sobre fenotipos cuantitativos biológicos y conductuales, permitiendo la identificación de genes individuales (genes cuantitativos) con acción sobre aquéllos. Presentamos el primer estudio de este tipo con ratas genéticamente heterogéneas (N/Nih-HS; derivadas de ocho cepas de ratas consanguíneas), que se evalúan en varias pruebas conductuales que miden ansiedad/miedo no aprendidos ('Caja blanca/negra', 'Laberinto en 'cero' elevado') o aprendidos (conducta de petrificación en contexto condicionado, adquisición de la evitación activa en dos sentidos en la caja de vaivén). Las ratas N/Nih-HS presentan una conducta más parecida a la de la cepa consanguínea RLA-I (ansiosas) que a la de la RHA-I (poco ansiosas). Se hallan correlaciones significativas entre variables incondicionadas de ansiedad y de la adquisición de la evitación activa en dos sentidos, confirmadas parcialmente por análisis de regresión múltiple. Las ratas N/Nih-HS relativamente 'evitadoras' exhiben niveles más bajos de ansiedad no aprendida que las poco 'evitadoras'. Los resultados de esta evaluación del comportamiento de las ratas N/Nih-HS son discutidos en términos de su potencial utilidad para la investigación neurogenética de la ansiedad y el miedoThe use of genetically heterogeneous (outbred) rodents is a unique resource for the identification and fine mapping of genetic loci (QTL) influencing biological and behavioural quantitative phenotypes, allowing the identification of quantitative genes. We present the first study of this kind carried out with genetically heterogeneous rats (N/Nih-HS; derivated from an eight-way cross of inbred strains), whose behaviour is assessed in tests evoking unlearned (Black/white box, Elevated 'zero' maze) or learned (context conditioned freezing, two-way active avoidance acquisition in the shuttlebox) anxious/fearful responses. The behavioural profile of N/Nih-HS rats is more similar to that of RLA-I (anxious) rats rather than to RHA-I (low anxious) rats. Significant correlations are found among unconditioned anxiety variables and two-way active avoidance acquisition in the shuttlebox; these are partially confirmed by multiple regression analysis. 'High avoider' N/Nih-HS rats show lower unlearned anxiety levels than 'low avoiders'. Results of this behavioural assessment of the N/Nih-HS rats are discussed in terms of their potential usefulness for present and future neurobehavioural and genetic studies of fearfulness and anxiet

Temerositat en rates heterogènies (N/Nih-HS) : vers els gens quantitatius de l'ansietat i la por /

Consultable des del TDXTítol obtingut de la portada digitalitzadaTesi doctoral - Universitat Autònoma de Barcelona, Facultat de Medicina, Departament de Biologia Cel·lular, Fisiologia i Immunologia, 2008En l'estudi de l'ansietat, models animals com ara les soques de rates Roman High i Low-Avoidance (RHA-I i RLA-I respectivament), seleccionades per llur alta o baixa adquisició de l'evitació activa en dos sentits, han demostrat tenir una gran validesa. A la primera part d'aquest treball es presenta l'avaluació d'aquestes soques a la prova de resposta de sobresalt potenciada per por i a la de condicionament de por clàssic. Tal com seria predictible, en base a la seva conducta en altres proves d'ansietat, les rates RLA-I van mostrar més potenciació per por de la resposta de sobresalt i més condicionament de por, mesurat com a resposta de petrificació. En la segona part es presenta, per primera vegada, l'avaluació conductual d'una gran mostra de rates genèticament heterogènies N/Nih-HS en una bateria de sis proves d'ansietat incondicionada i condicionada. Les soques genèticament heterogènies són una eina molt valuosa pels estudis de mapeig genètic d'alta resolució de «QTLs» (Quantitative Trait Loci), que poden permetre la identificació de gens. L'anàlisi factorial de les dades mostra una estructura multidimensional de les conductes relacionades amb la por i l'ansietat. En tots dos sexes, s'obté ha un primer factor anomenat de «Timidesa» que agrupa totes les variables relacionades amb la por de les proves incondicionades, i un segon factor en el que pesen les mesures de resposta de sobresalt («Fugida defensiva»). Així, el present treball proporciona evidència de que existeixen relacions entre conductes d'ansietat incondicionades i d'altres condicionades. Els diferents tipus d'anàlisis estadístiques mostren resultats coherents, proporcionant per tant un cert índex de consistència interna. Els resultats d'aquest treball representen un bon punt de partida per al posterior estudi de marcadors genètics («QTLs») de la conducta ansiosa en rates. De fet, es presenten dades preliminars que indiquen l'existència d'un QTL per a la conducta ansiosa, obtingut amb mètodes d'alta resolució, a la posició 100 Mb del cromosoma 5 de les rates N/Nih-HS. En la regió cromosòmica definida per aquest QTL es troben menys d'una desena de gens coneguts. Actualment, s'estan portant a terme estudis per avaluar la possible expressió diferencial d'aquests gens en àrees cerebrals vinculades a l'ansietat i la por en les rates RHA-I (poc ansioses) i RLA-I (molt ansioses)

The Roman high- and low- avoidance rat strains differ in fear-potentiated startle and classical aversive conditioning

The Swiss sublines of Roman High-(RHA/Verh) and Low-(RLA/Verh) Avoidance rats have been genetically selected (and outbred) since 1972 because of their good versus extremely poor acquisition of two-way, active avoidance. Inbred strains (RHA-I and RLA-I), derived from those two lines, have been maintained at our laboratory since 1997. The RLA line/strain shows increased stress-induced endocrine responses and enhanced anxiety/fearfulness in a variety of unconditioned behavioural variables and tests. Thus far, however, the Roman rat strains have not been compared in procedures involving classical fear conditioning to cues or contexts. Therefore, the present work was aimed at comparing RHA-I and RLA-I rats in 1) two different procedures of fear-potentiated startle and 2) in a classical fear conditioning (i.e., conditioned freezing) paradigm. The results indicate that, compared to RHA-I rats, RLA-I animals display higher levels of conditioned fear (as measured either by startle responses or freezing behavior) across those different tasksLas sublíneas suizas de ratas Romanas «High»-(RHA/Verh) y «Low»-(RLA/Verh) «Avoidance» han sido seleccionadas genéticamente, desde 1972, en función de su excelente (RHA) o extremadamente pobre adquisición de la tarea de evitación activa en dos sentidos. Cepas consanguíneas (RHA-I y RLA-I), derivadas de las dos líneas anteriores, se mantienen en nuestro laboratorio desde 1997. En comparación con la cepa RHA-I, la cepa RLA-I muestra incrementos en las respuestas hormonales al estrés, así como en conductas de ansiedad/miedo en una variedad de pruebas y variables conductuales incondicionadas. Hasta la fecha, las cepas de ratas Romanas no han sido comparadas en procedimientos de condicionamiento clásico de miedo a contextos o estímulos discretos. El presente trabajo tuvo como objetivo comparar ambas en 1) dos procedimientos de medida de la respuesta de sobresalto potenciada por miedo; y, 2) en un procedimiento de condicionamiento clásico de miedo (petrificación condicionada). Los resultados indican que las ratas RLA-I muestran niveles mayores de condicionamiento de miedo (respuesta de sobresalto y respuesta de petrificación) que las RHA-I, reforzando así los perfiles diferenciales de ansiedad/miedo de las dos cepa

The Roman High-and Low-Avoidance rat strains differ in fear-potentiated startle and classical aversive conditioning

The Swiss sublines of Roman High-(RHA/Verh) and Low-(RLA/Verh) Avoidance rats have been genetically selected (and outbred) since 1972 because of their good versus extremely poor acquisition of two-way, active avoidance. Inbred strains (RHA-I and RLA-I), derived from those two lines, have been maintained at our laboratory since 1997. The RLA line/strain shows increased stress-induced endocrine responses and enhanced anxiety/fearfulness in a variety of unconditioned behavioural variables and tests. Thus far, however, the Roman rat strains have not been compared in procedures involving classical fear conditioning to cues or contexts. Therefore, the present work was aimed at comparing RHA-I and RLA-I rats in 1) two different procedures of fear-potentiated startle and 2) in a classical fear conditioning (i.e., conditioned freezing) paradigm. The results indicate that, compared to RHA-I rats, RLA-I animals display higher levels of conditioned fear (as measured either by startle responses or freezing behavior) across those different tasksLas sublíneas suizas de ratas Romanas «High»-(RHA/Verh) y «Low»-(RLA/Verh) «Avoidance» han sido seleccionadas genéticamente, desde 1972, en función de su excelente (RHA) o extremadamente pobre adquisición de la tarea de evitación activa en dos sentidos. Cepas consanguíneas (RHA-I y RLA-I), derivadas de las dos líneas anteriores, se mantienen en nuestro laboratorio desde 1997. En comparación con la cepa RHA-I, la cepa RLA-I muestra incrementos en las respuestas hormonales al estrés, así como en conductas de ansiedad/miedo en una variedad de pruebas y variables conductuales incondicionadas. Hasta la fecha, las cepas de ratas Romanas no han sido comparadas en procedimientos de condicionamiento clásico de miedo a contextos o estímulos discretos. El presente trabajo tuvo como objetivo comparar ambas en 1) dos procedimientos de medida de la respuesta de sobresalto potenciada por miedo; y, 2) en un procedimiento de condicionamiento clásico de miedo (petrificación condicionada). Los resultados indican que las ratas RLA-I muestran niveles mayores de condicionamiento de miedo (respuesta de sobresalto y respuesta de petrificación) que las RHA-I, reforzando así los perfiles diferenciales de ansiedad/miedo de las dos cepas