Brain cholinesterase, body build and emotionality in different strains of rats

Rat strain and stock comparisons using a functional observational battery: baseline values and effects of amitraz

A functional observational battery (FOB) was utilized to assess the effects of 3-day exposure to the formamidine pesticide amitraz in outbred Sprague-Dawley-derived and inbred Fischer-344-derived (F344) rats (both from Charles River Laboratories) and in outbred Long-Evans rats obtained from two commercial suppliers (Charles River Breeding Laboratories and Blue Spruce Farms). Significant strain and stock differences were obtained in baseline values for one-third of the FOB measures. In most cases, F344 rats were different from the others. Characteristic signs of amitraz exposure consisting of increased excitability, hyper-reactivity, and physiological and autonomic changes were evident in all treated rats. These effects increased with repeated dosing, and many were still present 6 days after dosing. On individual measures, there were differences between the strains and stocks in terms of sensitivity and time course of amitraz effects. In general, Blue Spruce Long-Evans rats displayed more effects of amitraz and F344 rats recovered more quickly than others. Although Sprague-Dawley rats showed the least effect overall, they displayed the largest increases in the sensorimotor responses to stimuli. These data indicate that although some behavioral and physiological parameters showed strain and supplier differences, in both baseline values and the effects of amitraz, conclusions concerning its neurotoxic potential in a screening context would be similar.

A factor analysis of body build in the rat

Following a survey of the problems associated with the comparative study of measures of physique in domesticated and laboratory animals, techniques were developed for the measurement of body build in the adult albino laboratory rat (Rattus norvegicus). They involved anesthetisation of the animals and the use of calipers and a simple apparatus devised for the purpose. The 17 measures taken on 100 rats, 50 of each sex, are detailed and the reasons for excluding other given. Intercorrelations of all the measures and their reliability co-efficients, which were judged satisfactory, are presented. The tables of intercorrelations, one for each sex, were factor analysed separately, and rotations to simple structure performed. Two factors were identified, one having factor saturations on measures of body length and the other similarily defining body width. This pattern was similar for the two sexes and a single index of body build was therefore proposed in which the length of the rear foot is divided by the width of the shoulder girdle and multiplied by 100 to avoid decimals. The use of the index in other investigations is mentioned.

The Maudsley reactive and nonreactive strains of rats: a survey

Experiments with two strains of rats, the Maudsley Reactive and Nonreactive, developed in London, England, and which were performed during 1964--1974 by a variety of investigators are summarized in a table. It is concluded that the results support the strains' standing as exemplars of differences in emotional reactivity.

Stability and change in the inheritance of behaviour in rats: a further analysis of statistics from a diallel cross

Measurements made in the open-field test of the ambulation and defecation scores of rats from a 6 x 6 diallel cross were examined for their bearing on the interaction of genetic and environmental determinants of behaviour. The analyses, which were developed especially for this purpose, relate both to developmental stability and change in response to the test situation on 4 successive days. For the first, family variances were used as the variable, and for the second both polynomial components of regression of the individual daily scores as well as heirarchical analysis of variance. Otherwise standard biometrical genetical analyses were employed. The results indicate that, while the stability of open-field defecation and ambulation is influenced during development by genetical determinants largely relating to dominance, there is little evidence of interaction with environment during this time. The analyses of response to test experience, however, show complex relationships which, moreover, differ as between the two aspects of behaviour studied. Some speculations about the evolutionary significance of these results are offered.