Similar to humans, animals show systematic interindividual differences. For example, rats can differ in their locomotor response to a novel environment, and these differences were found to be linked to mechanisms of addiction and stress, and to the neurotransmitter dopamine (Dellu et al. Neuropsychobiology 34ī1996).
Apart from locomotion, the ratīs behavioural response to novelty is typically characterized by rearing behaviour. Recently (Thiel et al. Neuroscience 85ī98), we showed, that the rearing response induced by a novel environment is linked to interindividual differences in habituation learning and hippocampal acetylcholine: animals with a high response in the novel open-field showed higher cholinergic reactivity and more pronounced habituation than animals with a low response.
Here, we show how these differences in rearing behaviour are related to other behavioural measures. Due to habituation in high responders, the differences between high and low responders disappear with testing, but can partly be reinstated by the anticholinergic drug scopolamine. In contrast to the open-field, there are no major differences between high and low responding rats in the plus-maze, arguing against major differences in anxiety. Neurochemically, high responding rats have higher dopamine levels in the ventral striatum together with lower serotonin levels in the medial frontal cortex. The functional implications of these findings will be discussed, especially with respect to the role of dopaminergic and cholinergic mechanisms in the forebrain. (Supported by the DFG)
Referat in der Gruppe Psychopharmakologie/ -endokrinologie, Mittwoch, 31. März 1999, 16:00, HS 15
