While the regenerating capacity of peripheral nerves has been the subject of intensive study, little is known about the regenerative capacity of the autonomic nervous system. Using an animal model, where the pupil diameter of the eye in the rat serves as a parameter of autonomic function, we studied whether systemic treatment with the neuropeptide Org 2766, a synthetic ACTH4-9, analogue, facilitates the functional recovery of parasympathetic nerve fibres after transection, and after a crush lesion of the oculomotor nerve. By simply photographing the rat's pupil under standardised conditions, we show that sectioning the oculomotor nerve leads to an immediate mydriasis, followed by spontaneous regeneration in 30 days. Systemic treatment with an ACTH4-9 analogue had no effect on the rate or quality of recovery. However, systemic treatment with an ACTH4-9 analogue after a crush lesion of the oculomotor nerve (spontaneous regeneration time 16 days) did enhance the speed of recovery of the parasympathetic nerve fibres in the oculomotor nerve, especially in the initial stages of regeneration. We conclude that the animal model used in this study is valuable for studying the regenerative capacity of the autonomic nervous system and the influence of neurotrophic peptides on autonomic neuropathies. Evidence is presented that synthetic ACTH4-9 analogue exerts beneficial neurotrophic effects, not only in peripheral sensorimotor neuropathies but also in autonomic neuropathies.