NEUROANATOMICAL DISTRIBUTION OF VASOTOCIN IN A URODELE AMPHIBIAN (TARICHA-GRANULOSA) REVEALED BY IMMUNOHISTOCHEMICAL AND IN-SITU HYBRIDIZATION TECHNIQUES

Immunohistochemical and in situ hybridization techniques were used to investigate the neuroanatomical distribution of arginine vasotocin-lik e systems in the roughskin newt (Taricha granulosa). Vasotocin-like-im munoreactive neuronal cell bo dies were identified that, based on topo graphical position, most likely are homologous to groups of vasopressi n-immunoreactive neuronal cell bodies described in mammals, including those in the bed nucleus of the stria terminalis, medial amygdala, bas al septal region, magnocellular basal forebrain-including the horizont al limb of the diagonal band of Broca, paraventricular and supraoptic nuclei, suprachiasmatic nucleus, and dorsomedial hypothalamic nucleus. Several additional vasotocin-like-immunoreactive cell groups were obs erved in the forebrain and brainstem regions; these observations are c ompared with previous studies of vasotocin- and vasopressin-like syste ms in vertebrates. Arginine vasotocin-like-immunoreactive fibers and p resumed terminals also were widely distributed with high densities in the basal limbic forebrain, the ventral preoptic and hypothalamic regi ons, and the brainstem ventromedial tegmentum. Based on in situ hybrid ization studies with synthetic oligonucleotide probes for vasotocin an d the related neuropeptide mesotocin, as well as double-labeling studi es with combined immunohistochemistry and in situ hybridization, we co nclude that the vasotocin immunohistochemical procedures used identify vasotocin-like, but not mesotocin-like, elements in the brain of T. g ranulosa. The distribution of arginine vasotocin-like systems in T. gr anulosa is greater than the distribution previously reported for any o ther single vertebrate species; however, it is consistent with an emer ging pattern of distribution of vasotocin- and vasopressin-like peptid es in vertebrates. Complexity in the vasotocinergic system adds furthe r support to the conclusion that this peptide regulates multiple neuro physiological and neuroendocrinological functions. (C) 1997 Wiley-Liss , Inc.