Molecular correlates of emotional learning using genetically selected rat lines.

The genetic contributions to active avoidance learning in rodents have been well established, yet the molecular basis for genetically selected line differences remains poorly understood. To identify candidate genes influencing this active avoidance paradigm, we utilized the bidirectionally selected Syracuse high- and low-avoidance (SHA and SLA) rat lines that markedly differ in their two-way active avoidance behavior. Rats were phenotyped, rested to allow recovery from testing stress and then hippocampi were dissected for gene expression profiling (Affymetrix U34A chips; approximately 7000 known genes), comparing SLA to SHA.

Selection for differences in avoidance learning: the Syracuse strains differ in anxiety, not learning ability.

In this review the derivation of the Syracuse (SHA/Bru and SLA/Bru) strains of hooded rats that were selectively bred for differences in active two-way shuttle-box avoidance learning is described, together with a summary of the behavioral, hormonal, anatomical, physiological, and pharmacological characteristics that covary with the realized phenotypes. A selective genetic analysis is also described, which indicates that all of the five assessed covariates cosegregate with the avoidance phenotypes and are, therefore, closely linked to the high- and low-avoidance genotypes, which also suggests that a relatively few closely linked genes underlie the realized phenotypes. The low-avoidance phenotype seems best characterized in terms of high levels of state/trait anxiety, whereas the reverse is true of the high-avoidance phenotype.

The Syracuse strains, selectively bred for differences in active avoidance learning, may be models of genetic differences in trait and state anxiety.

The derivation of the Syracuse high- and low-avoidance strains is described. The behavioral characterization of the high- and low-avoidance phenotypes is summarized and it is concluded that the SLA/Bru strain is best described as having higher state and trait anxiety than their SHA/Bru counterparts. Although the behavioral covariates of the high- and low avoidance phenotypes are consistent, the covariation of the endocrine system normally thought to be involved in stress, is anomalous.

A selective genetic analysis of the Syracuse high- and low-avoidance (SHA/Bru and SLA/Bru) strains of rats (Rattus norvegicus).

Selective breeding of Long-Evans rats for good and poor avoidance learning in a two-way shuttle box resulted in the Syracuse strains that differ markedly in the selected phenotypes. These phenotypes have many associated traits, five of which are studied here: emotionality (open-field defecation), Pavlovian fear conditioning (CER suppression), passive avoidance training (punishment), size (weight) of the adrenal glands and adrenal concentration of corticosterone. Specifically, animals of the low-avoidance strain are more emotional, show greater fear conditioning, exhibit faster passive avoidance learning, and have larger adrenal glands in which adrenal corticosterone levels are lower than those of the high-avoidance strain.