Some pharmacological properties of RX 67668--a new anticholinesterase.

first detectable at approximately 12 days and reached adult levels at about 56 days. The relationship between ACh content and ChAc activity within each corneal extract was also logarithmic. Compared with ACh and ChAc, AChE activity showed less variation among different families and an entirely different relationship to age. A sharp peak in AChE was observed in the region of 3-10 days, and activity levelled off at adult values at values at about 25 days. The coincidence of the opening of the immature rabbit's eyelids (approximately 10 days after birth) with the first appearance of ACh and ChAc in the epithelium, together with the long time taken to achieve maturity of the cholinergic system, do not support a neural role for the bulk of ACh in the cornea.