Immunohistochemical localization of atrial natriuretic factor and autoradiographic distribution of atrial natriuretic factor‐binding sites in the brain of the cave salamander Hydromantes genei (Amphibia, Plethodontidae)

Abstract

The distribution of atrial natriuretic factor (ANF)-like immunoreactivity in the central nervous system of the cave salamander Hydromantes genei (Amphibia, Plethodontidae) was investigated by using antisera raised against rat and human ANF(1-28). Concurrently, the location of ANF-binding sites was determined by autoradiography, using radioiodinated human ANF(1-28) as a tracer. In several regions of the brain, including the olfactory bulb, the preoptic area, the ventral thalamus, the tectum of the mesencephalon, and the choroid plexuses inside the ventricles, a good correlation was observed between the distribution of ANF-immunoreactive elements and the location of ANF-binding sites. Mismatching was found in the habenular nucleus, the commissura habenularis, the fasciculum retroflexus, and the interpeduncular nucleus, which contained high levels of binding sites but were devoid of ANF-immunoreactive structures. In contrast, a few other regions, such as the pineal gland and the subcommissural organ, showed a high concentration of ANF-like immunoreactivity but did not contain ANF-binding sites. This study provides the first localization of ANF-like immunoreactivity and ANF-binding sites in the brain of an urodele amphibian. The results show that the ANF peptidergic system in the cave salamander has an organization more simple than the organizations described for the brain of frog or other vertebrates. This feature is probably related to the expression of highly pedomorphic characters in plethodontids. The anatomical distribution of ANF-immunoreactive elements and ANF-binding sites suggests that ANF-related peptides may act as hypophysiotropic hormones as well as neurotransmitters and/or neuromodulators in the salamander brain.

Somatostatin in the brain of the cave salamander, Hydromantes genei (Amphibia, Plethodontidae): Immunohistochemical localization and biochemical characterization

“…The Plethodontids are a group of urodeles characterized by a relatively simple brain architecture, due to the presence of a high degree of pedomorphosis (Roth et al, 1993). Several brain structures are less differentiated in salamanders than in outgroups, including cartilaginous and bony fishes and agnathans (Mathieu et al, 2001). A detailed cladistic analysis of 23 neural characters in sensory systems and brain has demonstrated that 19 of them are most parsimoniously interpreted as secondary simplified from a more complex ancestral condition (Roth et …”