Neurochemical features of the innervation of respiratory organs in some air-breathing fishes

A number of studies has been performed in recent years regarding the structure of the autonomic innervation of the gill and various organs of fishes, but only limited information exists on the role of the autonomic nervous system in air-breathing organs. The mechanisms for physiologically integrating gill and air-breathing organs are also not fully understood. The presence of neuropeptides and nNOS in gill autonomie nerves has been investigated in recent years by several Authors. Immunohistochemical localization of neuropeptides and nNOS in the autonomie nerves in the vasculatures and smooth muscle of air-breathing organs is reported for the first time. The function of NO in these tissues also remains to be elucidated especially, when the bulk of neurotransmission is attributable to cholinergic and adrenergic mechanisms. A challenge for future years is to understand the role of the autonomie nervous systems and the vasoactive substances in the in-series and in-parallel vascular connections between systemic gill and air-breathing organs.