Age-related scopolamine effects on social and individual behaviour in rats.

The modulation of spontaneous (social and individual) behaviour as a function of the age of the rat (1, 3, 6, 12, 18 and 24 months) and of scopolamine dose (0.1, 0.2, 0.3 and 0.5 mg/kg) was studied. Observations were conducted during the dark phase of the reverse light/dark schedule using a reintroduction procedure. Results showed a marked effect of scopolamine on most of the behavioural patterns considered. Environmental interaction was enhanced whilst agonistic and social active interactions (social grooming) and play fighting were reduced by the drug. A slight hyposensitivity in the youngest rats and a marked hyposensitivity to the drug in the oldest ones were observed. The relationship to biochemical data and human sensitivity on the one hand and to learning and memory tasks and cholinergic specificity on the other hand, are discussed.