Autonomic nerves containing substance P in the aqueous outflow channels and scleral spur of the guinea pig

Purpose: To study the innervation of the aqueous outflow channels and scler al spur by autonomic nerves containing substance P. Methods: The experiments were conducted on guinea pigs. Immunohistochemical techniques and capsaicin-ablation of the sensory nerves were used to inves tigate nerves containing substance P at the light and electron microscopic level. Results: Nerves containing substance P were observed in the aqueous outflow channels and scleral spur regions. The fine structures of these nerves had a similar pattern in those regions, and the labeled elements had abundant small vesicles, a few large vesicles, and numerous neurotubuli. Following c apsaicin treatment. these nerves remained intact and no degenerated substan ce P-like immunoreactive nerves were found. Conclusions: Nerves containing substance P are most likely of autonomic ori gin in view of their ultrastructural features. These nerves innervate the a queous outflow channels and scleral spur, and are probably important for ne urogenic influences on the intraocular pressure by the autonomic nervous sy stem. Jpn J Ophthalmol 1999;43:272-278. (C) 1999 Japanese Ophthalmological Society.