THE USE OF THE RAT IRIS AS A MODEL SYSTEM TO EVALUATE THE EFFECT OF THE CHOLINOTOXIN, AF64A, IN-VIVO

The iris is innervated by both cholinergic parasympathetic, and adrene gic sympathetic branches of the autonomic nervous system. This innerva tion represents a simple and anatomically well-defined system to evalu ate the effects of chemical compounds on cholinergic and adrenergic ne urons. AF64A (acetyl ethylcholine aziridinium) is a known cholinotoxin in the brain and, in these experiments using the iris system, we eval uated its in vivo effect on cholinergic enzyme activity, pupillary siz e, and catecholamine neurotransmitter levels. We found in this system that AF64A reduces the activity of choline acetyltransferase (ChAT) bu t not acetylcholinesterase (AChE). AF64A is selective for cholinergic neurons, since norepinephrine and dopamine levels were unaffected.