Complex innervation patterns of the conus arteriosus in the heart of the longnose gar, Lepisosteus osseus.

Anatomical and functional studies of the autonomic innervation in the conus arteriosus of the garfishes
are lacking. This study reveals that the conus arteriosus of the longnose gar is primarily myocardial in
nature, but additionally, large numbers of smooth muscle cells are present in the subendocardium.Awelldeveloped
system of adrenergic, cholinergic, substance P (SP) and neuronal nitric oxide synthase (nNOS)
positive nerve terminals are found in the wall of the conus arteriosus. Coronary blood vessels running
in the adventitia receive a rich supply of nNOS positive nerve fibers, thus suggesting their importance
in the nitrergic control of blood flow in the conus arteriosus. The present data show that the patterns of
autonomic innervation of the garfish conus arteriosus are more complex than previously appreciated.