The intrinsic origin of nitric oxide synthase immunoreactive nerve fibers in the right atrium of the guinea pig

We previously reported three kinds of nitric oxide synthase-immunoreactive (NOS-ir) axons in the guinea pig heart: the sparse fiber network covering t he right atrium, the basket-like endings around intracardiac neurons, and t he axons in the septal region. The sparse NOS-ir nerve fiber network in the right atrium remained after vagotomy and has been suggested to be originat ed from intrinsic cardiac ganglia. Using Chorera toxin B as a retrograde tr acer, we determined a part of them were derived from cardiac ganglionic neu rons located in the area near the vena cavae. (C) 2001 Elsevier Science Ire land Ltd. All rights reserved.