Distribution of vasoactive intestinal peptide-like immunoreactivity in thebrain and pituitary of the frog (Rana esculenta) during development

The localization of vasoactive intestinal peptide (VIP)-like immunoreactive (ir) elements was investigated in the brain of the anuran amphibian, Rana esculenta, during development. Using an antiserum raised against the porcin e VIP, ir cell bodies and fibers were observed in the forebrain of tadpoles a few days after hatching. During early premetamorphosis, ir perikarya wer e distributed in the ventral infundibular nucleus of the hypothalamus and i n the posterocentral nucleus of the thalamus. Labeled fibers were detected in the olfactory bulbs and in the hypothalamus. In these larvae, furthermor e, several VIP-ir cells were found in the pars distalis of the pituitary an d there were ir fibers in the pars nervosa. In tadpoles at stages VIII-IX, a new group of VIP-labeled neurons was observed in the dorsal part of the i nfundibular nucleus. In other brain regions, the distribution of the immuno reactivity was similar to that described in the earliest stages, i.e., IV-V II. During mid-premetamorphosis, stages X-XII of development, an additional set of ir perikarya appeared in the ventrolateral area of the thalamus. Du ring late premetamorphosis, stages XIII-XVIII, the organization of VIP-Like immunoreactivity was more complex and its distribution more widespread. Tw o new groups of ir cell bodies appeared, one in the preoptic nucleus and an other in the anteroventral area of the thalamus, and for the first time, VI P immunoreactivity was observed in the median eminence. This distribution p attern persisted through to the prometamorphic, four-limb stage. Strikingly , no VIP-ir elements were observed anywhere in the mid- and hindbrain. The present results indicate that a VIP-like ir peptide may be involved in the processing of olfactory information or may act as a neurohormone, hypophysi otropic factor, and neuromodulator in the brain of R. esculenta during deve lopment. (C) 1999 Elsevier Science B.V. All rights reserved.