The validity of scopolamine as a pharmacological model for cognitive impairment: a review of animal behavioral studies.

Scopolamine is used as a standard/reference drug for inducing cognitive deficits in healthy humans and animals. Effects are often interpreted in terms of a role of acetylcholine in mnemonic and/or attentional processes. In this paper an overview is given of the effects of scopolamine on animal behavior. Examination of the dose-response curve of systemically administered scopolamine indicates that sensory discrimination and attention are most sensitive to disruption. When higher doses (>0.03mg/kg) are used, deficits in other cognitive and non-cognitive functions (e.g., learning and memory, locomotor activity) are reported. Several behavioral processes (taste aversion, anxiety, short-term memory, attention) are found to be affected after intracerebral injections of scopolamine. It is concluded that effects on learning and memory performance which are observed after higher doses of scopolamine are mediated by (1) primary effects on attention and sensory/stimulus discrimination, (2) non-specific effects on behavior (e.g., locomotor activity, anxiety), and (3) peripheral side-effects (e.g., pupil dilation, salivation). Finally, the validity of scopolamine as a pharmacological model for cognitive impairment is discussed. The use of muscarinic M1 antagonists is suggested as a more selective and effective way of inducing cholinergic-induced cognitive deficits.