[Acetylcholine of bovine iris and cholinergic effects of pilocarpine].

The authors extracted acetylcholine (ACh) from bovine iris and carried out biological assay on guinea pig ileum. One of the pairs of irides were subjected in vivo for an hour to an aqueous solution of pilocarpine HCl 3 per cent, with the loading dose instilled in the conjunctival sac at the rate of ten times three drops in intervals of three minutes. The bio-assays of tissue extracts of pilocarpinised iris after one hour's action and the control studies present the following values: the amount of ACh in the pilocarpinised irides was 0,70 mug and in the controls it was 0,58 mug of ACh/150 mg of tissue. The remaining proportion of the elevated dose of pilocarpine applied to the iris tissue, one hour after the in vivo action, was comparable only to 1,5 mug of free pilocarpine or to a fifth of the ACh in the iris (0,12 mug). The results of these experiments demonstrate a complete decomposition of the pilocarpine as well as the existence of a certain limitation of elevation of the cholinergic tone in the iris tissues. The authors support data in the literature which indicates that pilocarpine raises the ACh levels. They do not attribute a fundamental importance to the raised loading dose of pilocarpine concerning the desired effect of a maximal elevation of cholinergic tone in order to achieve a favourable clinical effect in glaucoma.