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The Roman high- (RHA-I) and low-avoidance (RLA-I) rat strains are bi-directionally bred for their good versus non-acquisition of two-way active avoidance, respectively. They have recently been re-derived through embryo transfer (ET) to Sprague-Dawley females to generate specific pathogen free (SPF) RHA-I/RLA-I rats. Offspring were phenotyped at generations 1 (G1, born from Sprague-Dawley females), 3 and 5 (G3 and G5, born from RHA-I and RLA-I from G2-G4, respectively), and compared with generation 60 from our non-SPF colony. Phenotyping included two-way avoidance acquisition, context-conditioned fear, open-field behaviour, novelty-seeking, baseline startle, pre-pulse inhibition (PPI) and stress-induced increase in plasma corticosterone concentration. Post-ET between-strain differences in avoidance acquisition, context-conditioned freezing and novelty-induced self-grooming are conserved. Other behavioural traits (i.e. hole-board head-dipping, novel object exploration, open-field activity, startle, PPI) differentiate the strains at G3-G5 but not at G1, suggesting that the pre-/post-natal environment may have influenced these co-segregated traits at G1, though further selection pressure along the subsequent generations (G1-G5) rescues the typical strain-related differences.

The present study explored the effects of infantile stimulation (i.e., neonatal handling or NH) on the performance of 18-month-old Roman high-avoidance (RHA/Verh) and low-avoidance (RLA/Verh) rats in a swimming pool matching-to-place (SPMP) test. This test (also called repeated acquisition and place learning-set paradigm) consists of administering pairs of consecutive trials in the Morris water maze. The difference between each “odd” and the consecutive “even” trial of a trial pair is considered to be a measure of working memory. The same rats were first tested for exploration and novelty-seeking in a hole-board test in the presence of novel objects, which showed that RHA/Verh rats were more explorative than their RLA/Verh counterparts, and that NH treatment augmented exploration in RLA/Verh rats, generally eliminating the genetically-based differences between the lines. RHA/Verh rats performed less efficiently than RLA/Verh rats in the SPMP test, and NH facilitated acquisition in the early stages of training in both rat lines, an effect that was presumably due to an improvement in the acquisition of spatial reference information. Performance during training also indicated that RHA/Verh rats showed less differentiated behavior between odd and even trials, indicating a relative working memory deficit at advanced ages in that rat line.

Male and female rats of the inbred Roman/Verh strains, which have been psychogenetically selected and bred for good (RHA-I/Verh) and extremely poor (RLA-I/Verh) two-way avoidance acquisition, were evaluated in an acoustic startle response test. One half of the rats of each strain and sex were previously subjected to 30 min of isolation by removal of their cage partners (“cohort removal”). During the testing session each animal received 40 acoustic stimuli at interstimulus intervals of 30 seconds. The hyperemotional RLA-I/Verh rats (especially the males) showed stronger acoustic startle responses than did their RHA-I/Verh counterparts. Startle amplitudes of the RLA-I/Verh males were further enhanced by the stress of 30 min isolation, whereas cohort removal did not significantly affect startle response amplitudes in RHA-I/Verh rats of either sex or in females of the RLA-I/Verh strain.

An inbreeding program has been carried out with the Swiss sublines of Roman high- and low-avoidance rats since 1993. The present study reports the first experiments conducted with young animals of those inbred strains (RHA-I/Verh and RLA-I/Verh, respectively) from the sixth and seventh inbreeding generations. The results confirmed expected behavioral profiles. Compared to the RHA-I/Verh strain, RLA-I/Verh rats showed decreased entries into the illuminated central arena of an hexagonal tunnel maze, as well as decreased spontaneous locomotor activity and increased defecations, in two independent experiments. Young RLA-I/Verh females explored less than did their RHA-I/Verh counterparts during session 1 of a conditioned-fear experiment preceding shock administration, and in session 2 (conducted 24 h after the application of three footshocks), they showed greater conditioned behavioral inhibition (i.e., reduced amount of rearing), as well as higher defecation scores, than did RHA-I/Verh females.

Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats are selected and bred for extreme divergence in two-way active avoidance acquisition. In addition, compared to RLA/Verh rats, RHA/Verh rats are (behaviorally and physiologically) less anxious or reactive to stressors, show increased novelty (sensation)-seeking behavior as well as a higher preference for rewarding substances, and are usually less efficient in learning tasks not involving shock administration. The present article reviews evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects (their magnitude frequently depending upon the rat line) on those behaviors. For example, it has been found that neonatal handling reduces most of the (behavioral and physiological) signs of emotionality/anxiety in RLA/Verh rats, while environmental enrichment increases their novelty seeking (also the case with RHA/Verh rats), saccharin and ethanol intake, and sensitivity to amphetamine. Finally, initial results (currently being further elaborated upon) support a preventive action of both environmental treatments on age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy.

The present study explored the effects of infantile stimulation (i.e., neonatal handling or NH) on the performance of 18-month-old Roman high-avoidance (RHA/Verh) and low-avoidance (RLA/Verh) rats in a swimming pool matching-to-place (SPMP) test. This test (also called repeated acquisition and place learning-set paradigm) consists of administering pairs of consecutive trials in the Morris water maze. The difference between each "odd" and the consecutive "even" trial of a trial pair is considered to be a measure of working memory. The same rats were first tested for exploration and novelty-seeking in a hole-board test in the presence of novel objects, which showed that RHA/Verh rats were more explorative than their RLA/Verh counterparts, and that NH treatment augmented exploration in RLA/Verh rats, generally eliminating the genetically-based differences between the lines. RHA/Verh rats performed less efficiently than RLA/Verh rats in the SPMP test, and NH facilitated acquisition in the early stages of training in both rat lines, an effect that was presumably due to an improvement in the acquisition of spatial reference information. Performance during training also indicated that RHA/Verh rats showed less differentiated behavior between odd and even trials, indicating a relative working memory deficit at advanced ages in that rat line.

Male and female rats of the inbred Roman/Verh strains, which have been psychogenetically selected and bred for good (RHA-I/Verh) and extremely poor (RLA-I/Verh) two-way avoidance acquisition, were evaluated in an acoustic startle response test. One half of the rats of each strain and sex were previously subjected to 30 min of isolation by removal of their cage partners ("cohort removal"). During the testing session each animal received 40 acoustic stimuli at interstimulus intervals of 30 seconds. The hyperemotional RLA-I/Verh rats (especially the males) showed stronger acoustic startle responses than did their RHA-I/Verh counterparts. Startle amplitudes of the RLA-I/Verh males were further enhanced by the stress of 30 min isolation, whereas cohort removal did not significantly affect startle response amplitudes in RHA-I/Verh rats of either sex or in females of the RLA-I/Verh strain.

Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats are selected and bred for extreme divergence in two-way active avoidance acquisition. In addition, compared to RLA/Verh rats, RHA/Verh rats are (behaviorally and physiologically) less anxious or reactive to stressors, show increased novelty (sensation)-seeking behavior as well as a higher preference for rewarding substances, and are usually less efficient in learning tasks not involving shock administration. The present article reviews evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects (their magnitude frequently depending upon the rat line) on those behaviors. For example, it has been found that neonatal handling reduces most of the (behavioral and physiological) signs of emotionality/anxiety in RLA/Verh rats, while environmental enrichment increases their novelty seeking (also the case with RHA/Verh rats), saccharin and ethanol intake, and sensitivity to amphetamine. Finally, initial results (currently being further elaborated upon) support a preventive action of both environmental treatments on age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy.

An inbreeding program has been carried out with the Swiss sublines of Roman high- and low-avoidance rats since 1993. The present study reports the first experiments conducted with young animals of those inbred strains (RHA-I/Verh and RLA-I/Verh, respectively) from the sixth and seventh inbreeding generations. The results confirmed expected behavioral profiles. Compared to the RHA-I/Verh strain, RLA-I/Verh rats showed decreased entries into the illuminated central arena of an hexagonal tunnel maze, as well as decreased spontaneous locomotor activity and increased defecations, in two independent experiments. Young RLA-I/Verh females explored less than did their RHA-I/Verh counterparts during session 1 of a conditioned-fear experiment preceding shock administration, and in session 2 (conducted 24 h after the application of three footshocks), they showed greater conditioned behavioral inhibition (i.e., reduced amount of rearing), as well as higher defecation scores, than did RHA-I/Verh females.

Two hundred forty 30-day-old Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats (divided equally by line and gender) which had received several peri- and/or postnatal treatments, forming two factorial [line x sex x treatment(s)] experimental designs, were tested in a hexagonal tunnel maze including a brightly illuminated central arena. The present study reports the results of correlational and factorial (principal-components) analyses performed on the data from those two experimental constituencies. The purpose of the study was to evaluate the validity of the hexagonal tunnel maze for testing emotionality, and therefore, the following measures were included in the analysis: entries into the central illuminated arena, total activity during testing, defecation during testing, and defecation during handling and weighing after testing. An overall pattern of negative correlations (or opposite loadings in the principal-components analyses) between defecation (especially during maze testing) and entries into the illuminated center and activity was found, thus giving support to the validity of entries into the illuminated center as being indicative of emotional reactivity.