Scopolamine reduces frontal cortex perfusion.

While the cognitive deficits of Alzheimer's disease are considered related to a cholinergic deficit, no attempt has yet been made to test the hypothesis that the characteristic regional cerebral blood flow (rCBF) pattern of Alzheimer's disease may also relate to such a deficit. We therefore measured rCBF using the [133Xe] inhalation technique in 15 young normal subjects before and after induction of reversible cholinergic blockade with scopolamine at doses of 6.1 and 7.3 micrograms/kg i.v. Significant cognitive impairment was observed at both doses, while rCBF changes occurred only at the higher dose. Global CBF was significantly reduced 25 min after scopolamine. The pattern of regional change in CBF was not similar to Alzheimer's disease. Rather than a focal parietotemporal deficit as seen in Alzheimer's disease, we observed a predominantly frontal reduction in flow of about 20%. These results suggest that the frontal but not the parietotemporal deficits seen in several dementing conditions may be related to cholinergic dysfunction.