Effects of organophosphate pesticides and other drugs on subcortical mechanisms of visual integration.

Atropine, scopolamine, mevinphos, and eserine selectively block directional sensitivity of visual integrative neurones in the thalamus. Cholinergic drugs that do not penetrate the blood-brain barrier are without effect. The neurones studied are important links in reflex brain systems controlling visual attention and eye movements. The results suggest that any cholinergic drug that can get into the brain will disturb visual functions. Since the changes are qualitative and the system is reflex, the affected individual may be unaware of dysfunction. The resultant dangers to aerial applicator personnel are discussed, particularly with respect to atropine, which is necessary in the therapy of organophosphate and carbamate poisoning but is potentially harmful if self-administered for either pro-phylaxis or treatment.