Nerve fibres containing neuropeptide Y in the atrioventricular valves of Japanese monkey and rat; a light and electron microscopic study.

Dense distribution of varicose fibres containing neuropeptide Y-like immunoreactivity (NPY-LI) was found in the atrioventricular valves of the Japanese monkey, and moderately in the rat. The immunoelectron microscopy using immunogolds resulted in the localization of NPY-LI within the dense-cored vesicles which existed with the small clear vesicles in the unmyelinated axons near the endocardium. These NPY-LI-containing fibres may participate in regulation of vasomotor role or other functions of the atrioventricular valves.