High versus low reactivity to a novel environment: behavioural, pharmacological and neurochemical assessments
Section snippets
Animals
Twenty-four male Wistar rats (RCC-BLR, Füllingsdorf, Switzerland), weighing between 250–300 g at the beginning of the experiment were used. They were housed individually under standard laboratory conditions and allowed free access to food and water. All animals were handled daily for three days prior to behavioural testing.
Drugs
Scopolamine (0.5 mg/ml; Sigma) was dissolved in 0.9% saline for i.p. injection. The injection volume was 1 ml/kg.
Open field testing
The open field consisted of a black wooden chamber (60×60×40 cm)
Results
Assigning the animals to sub-groups with high and low levels of rearings in the novel open field yielded the following behavioural and neurochemical profiles.
Discussion
The present work provides a pattern of behavioural and neurochemical differences between animals with high or low rearing responses in a novel open field (defined as HR vs LR rats). Besides the number of rearings, these sub-groups of animals also differed in their levels of locomotor activity. In contrast, other behavioural parameters (thigmotaxis, centre time, faecal boli) did not indicate differences between HR and LR rats in the novel environment. With repeated testing, rearing, scanning,
Conclusions
The current findings complement and extend the existing literature on differential behavioural responses to novelty in rats. Animals that showed higher rearing responses also differed from animals with low rearings in their locomotor response to novelty, in behavioural habituation, and in scopolamine-induced rearing. Neurochemically, these differential behavioural profiles might be mediated by systematic variations in striatal DA and frontal cortical serotonin function, together with
Acknowledgements
This work was supported by grant Schw 559/2-2 from the Deutsche Forschungsgemeinschaft. R. K. W. Schwarting is a Heisenberg-fellow of the Deutsche Forschungsgemeinschaft.19.33.59.
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