Pilocarpine toxicity in retinal ganglion cells.

Leonard Levin // Publications // Mar 01 1999

PubMed ID: 10067991

Author(s): Vorwerk CK, Simon P, Gorla M, Katowitz W, Zurakowski D, Levin LA, Dreyer EB. Pilocarpine toxicity in retinal ganglion cells. Invest Ophthalmol Vis Sci. 1999 Mar;40(3):813-6. PMID 10067991

Journal: Investigative Ophthalmology & Visual Science, Volume 40, Issue 3, Mar 1999

PURPOSE Muscarinic agents reduce intraocular pressure by enhancing aqueous outflow, probably by stimulating ciliary muscle contraction. However, pilocarpine is a well characterized neurotoxin and is widely used to generate animal seizure models. It was therefore investigated whether pilocarpine was also toxic to retinal ganglion cells.

METHODS Dissociated whole retinal preparations were prepared from postnatal day 16 to 19 rats. Retinal ganglion cells had been previously back-labeled with a fluorescent tracer. Retinal cells were incubated with pilocarpine, lithium, and inositol derivatives, and viability of the retrogradely labeled retinal ganglion cells was assayed after 24 hours.

RESULTS Pilocarpine was toxic to retinal ganglion cells in a dose-dependent fashion. This toxicity was potentiated by lithium and blocked by epi- and myo-inositol.

CONCLUSIONS Pilocarpine is toxic to retinal ganglion cells in a mixed culture assay. This toxicity appears to depend on the inositol pathway and is similar to its mode of action in other neurons. However, 0.4 mM pilocarpine (the lowest concentration that did not affect ganglion cell survival) is roughly 1000-fold higher than the vitreal concentration and 20-fold higher than the scleral concentration that can be obtained with topical administration of 2% pilocarpine in the rabbit eye.