Disordered cholinergic neurotransmission and dysautoregulation after acute cerebral infarction.

The possible role of displaced neurotransmitter acetylcholine (ACHh) in dysautoregulation was examined after experimental regional cerebral infarction was produced by occluding the middle cerebral artery (MCA) in babons. Regional cerebral blood flow (rCBF) was measured after intracarotid injection of 133Xenon using the gamma camera. Autoregulation was tested with metaraminol or angiotensin infusion and the autoregulation index (A.I.) was calculated. Acetylcholinesterase (ACHhE) was measured in brain tissue of noninfarcted and infarcted hemispheres. Cerebral arteriovenous (A-V) differences for cholinesterase (ChE) were also measured. Regional dysautoregulation was found in infarcted gray matter and correlated with increased AChE levels in the same zones of cortex and basal ganglia. The time course of onset of dysautoregulation correlated with increased ChE uptake by the brain. Intravenous infusion of the cholinergic neurotransmitter blocker, scopolamine, restored autoregulation to the ischemic zones. Autoregulation appears to be a myogenic reflex, influenced by neurogenic and metabolic mechanisms.