ACETYLCHOLINE IN RABBIT VISUAL SYSTEM NUCLEI AFTER ENUCLEATION AND VISUAL CORTEX ABLATION

¹ Departments of Pharmacology, Pediatrics, Medicine (Neurology) and Anatomy, University of Chicago, Chicago, Illinois

Acetylcholine in visual systen nuclei (dorsal lateral geniculate, superior colliculus and striate cortex) was (determined after orbital enucleation, ablation of the striate cortex or these lesions combined. Enucleation results in a substantial loss of optic nerve terminals from the contralateral dorsal lateral geniculate and superior colliculus. This lesion produces a 22.6% reduction in acetylcholine concentration in the dorsal lateral geniculate. Visual cortex ablation results in a loss of corticofugal terminals to the superior colliculus and dorsal lateral geniculate and marked retrograde degeneration with cell loss in the dorsal lateral geniculate. This lesion produces a 27.9% reduction in dorsal lateral geniculate acetylcholine content but no alteration in acetylcholine concentration since the lesion results in a corresponding weight loss in tile nucleus due to retrograde degeneration. Visual cortex ablation combined with unilateral enucleation causes a 55.9% decrease in the total acetvlcholine content of the affected dorsal lateral geniculate, resulting in a 35.2% decrease in concentration. Acetylcholine levels in the superior colliculus or striate cortex were unaffected by the visual system lesions used in this study. The results indicate that acetylcholine in the dorsal lateral geniculate is dependent upon the integrity of specific neurons in the visual system.