NEURAL INFLUENCES ON THE IRIS OF DIABETIC RATS AND EFFECT OF OCULOMOTOR NERVE CRUSH

Using an animal model where the pupil diameter of the eye in anaesthet ized and dark-adapted rats serves as a parameter of autonomic function , we studied the functional recovery of the parasympathetic nerve fibr es in the oculomotor nerve after a crush lesion in rats with streptozo tocin-induced diabetes compared with normal controls. Prior to the cru sh lesion, diabetic rats develop significantly (P < 0.001) smaller pup ils compared with controls, and this occurs early in the course of the diabetes mellitus. As the difference in pupil diameter between contro l and diabetic rats persists immediately after the crush lesion, when the nervous control of the pupil is entirely due to sympathetic nerves , we suggest that the reduction in pupil diameter is due to a sympathe tic neuropathy. Furthermore, we show that the functional recovery of t he parasympathetic input to the iris after a crush lesion of the oculo motor nerve is not as good in diabetic rats as it is in normal control rats.