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The innervation of the respiratory tract of amphibians is still poorly understood. Therefore, the respiratory tracts of the frogs Rana esculenta and Discoglossus pictus have been investigated in order to describe non-adrenergic non-cholinergic (NANC) and adrenergic innervation, and the localization of neuromediators that are possibly involved. Immunohistochemical staining of many bioactive substances was found in neuroepithelial cells of the buccopharynx, larynx, lung septa, nerves and neurons throughout the airway system. The findings indicate the occurrence of vasoactive intestinal peptide (VIP)-immunopositive nerve fibers in fibromuscular septa and the vasculature, nitrergic innervation of the large pulmonary veins showing a plexus of nNOS-immunopositive nerve fibers that also innervate the lung wall and the localization of neuronal nitric oxide synthase (nNOS) in neurons in the lung wall. In addition, laryngeal blood vessels and small arteries in the wall of septa that form capillary networks are supplied by enkephalin-immunopositive nerve terminals. We conclude that the airway system of the two frog species studied is innervated by a parasympathetic NANC system. Adrenergic innervation was also found that was immunostained for tyrosine hydroxylase. Adrenergic fibers were mainly present in muscles in septal edges, arteries present in septa and the wall of the lung. It is suggested that nNOS-positive and leu-enkephalin-positive neurons mediate vasodilation via the release of NO, but the nature of the NANC innervation remains obscure. Despite the many pharmacological studies of the lungs of amphibians, the physiological role of pulmonary autonomic innervation remains poorly understood.

The authors present an overview of the main amphibian peptide families mainly derived from the skin and mostly discovered by Erspamer and his associates. The studies of the peptides do not only promote the understanding of their chemical, metabolical and physiological features of those molecules in amphibians, but also contribute to progress in our knowledge of the corresponding mammalian counterparts. Particular reference is made on sauvagine, tachykinin, bombesin and dermorphin families, offering new data mostly from personal contributions to this field.

We report the presence of sauvagine/urotensin I-like immunoreactive (SV/UI-LI) elements in the caudal neurosecretory system of a teleost (Diplodus sargus L.) collected from aquaria tanks of the Aquaculture Center (Talassographic Institut of CNR) of Messina or maintained in an hyposmotic milieu for different periods. In normal specimens, SV/UI-LI material was recognizable in discrete or little amounts both in Dahlgren cell cytoplasm and in their axons that reach the urophysis. On the contrary, the specimens transferred in an hyposmotic milieu showed a fast and dramatic increase of immunoreactivity mainly in neurohemal endings of the urophysis. This suggests a physiological role of caudal neurosecretory products on osmoregulatory mechanisms.

Le indagini statistiche effettuate sui nucleoli degli ovociti diRana esculenta, Discoglossus pictus eTriturus cristatus hanno consentito di confermare che i nucleolini, assenti nei nucleoli piu piccoli, diventano sempre piu numerosi coll'aumentare delle dimensioni dei nucleoli. Nelle tre specie in esame sono stati altresi ottenuti coefficienti di correlazione approssimativamente simili.