Adrenergic innervation of the choroid and iris in diabetic rats

We compared the distribution and density of ocular adrenergic nerves in rats after 3 to 13 months of streptozotocin diabetes and in age-matched control animals to learn whether diabetic sympathetic neuropathy is evident in the eye as it is in other organs. An aqueous aldehyde method for histochemical demonstration of catecholamines provided a clear and complete view of the adrenergic innervation in whole flat preparations of choroid and iris. In the choroid, a dense plexus of varicose nerve fibers invested all of the branching arterial blood vessels. A less dense network of nerves was present in the choroidal stroma between the arteries, but there was no obvious association of nerves with the venules draining choroidal capillaries. Using a stereological method to measure the density of the adrenergic plexus of choroidal arteries, we found the mean innervation density to be normal in diabetic animals sampled at 3, 9, and 13 months after onset of hyperglycemia. Microscopic examination also failed to reveal diabetes-associated changes in the diffuse stromal nerves of the choroid or in the rich adrenergic innervation of the iris. Diabetes of relatively long duration, therefore, does not obviously affect the density or distribution pattern of catecholamine-containing nerves supplying the rat eye.