DISTRIBUTION OF SOMATOSTATIN-LIKE IMMUNOREACTIVITY IN THE BRAIN OF THE FROG, RANA-ESCULENTA, DURING DEVELOPMENT

The anatomical distribution of somatostatin-like immunoreactivity in t he central nervous system of the frog, Rana esculenta, during developm ent and in juvenile specimens was investigated by indirect immunofluor escence. Soon after hatching, at stages II-III, somatostatin-like immu noreactive structures were found in the preoptic-median eminence compl ex. In stage VI tadpoles, new groups of immunopositive perikarya and n erve fibers appeared in the diencephalon, within the ventral infundibu lar nucleus and in the ventral area of the thalamus, as well as in the medial pallium. In stages XII-XIV of development, immunopositive peri karya were also present in the dorsal infundibular nucleus of the hypo thalamus and ventrolateral area of the thalamus. A small group of soma tostatin-like immunoreactive neurons appeared in the posteroventral nu cleus of the rhombencephalon. However, these neurons were not seen in later stages of development. Tadpoles in stages XVIII, XXI-XXII and in juveniles were characterized by a wider distribution of immunoreactiv e cell bodies and fibers in the pallium. New groups of immunoreactive neurons were found in the dorsal and lateral pallium. The presence of positive perikarya in the lateral pallium is a transient expression fo und only in these stages. The organization of the somatostatinergic sy stem was most complex during the metamorphic climax, with the appearan ce of positive cell bodies in the posterocentralis area of the thalamu s, and in juvenile animals with the presence of perikarya in the ventr al part of the medial pallium and within the central grey rhombencepha li. In contrast to the adult frog, somatostatin neurons were not obser ved in the mesencephalon of tadpoles and juveniles. (C) 1998 Elsevier Science B.V.