Introduction [8–11,33,56,57]. In rat, inhibition of VIP functions during
Brain Research 888 2001 235–247 www.elsevier.com locate bres
Research report
Organization of vasoactive intestinal peptide-like immunoreactive system in the brain, olfactory organ and retina of the zebrafish,
Danio rerio, during development
Maura Mathieu , Grazia Tagliafierro, Cristiano Angelini, Mauro Vallarino
` Dipartimento di Biologia Sperimentale
, DIBISAA, Universita di Genova, Viale Benedetto XV, 5, 16132 Genova, Italy Accepted 3 October 2000
Abstract
The localization of vasoactive intestinal peptide VIP-like immunoreactivity was investigated in the brain, olfactory system and retina of the zebrafish, Danio rerio, during development and in juvenile specimens, by using the indirect immunofluorescence and the
peroxidase-antiperoxidase methods. In 24 h post fertilization hpf embryos, VIP-like immunoreactive cells were present in the olfactory pit, the retina, and several regions of the brain, including the dorsal telencephalon, the diencephalon, the tegmentum of the
mesencephalon, the caudal rhombencephalon and the anterior pituitary. In 48 hpf embryos, additional VIP-like immunoreactive cell bodies were found in the ventral telencephalon, whereas in the diencephalon VIP-like immunopositive cells were more concentrated
within the ventro-caudal hypothalamus. During the 7 day larval period, a dense plexus of VIP-like immunoreactive fibers first appeared in the olfactory bulbs. In 15-day-old larvae, two new groups of positive cells were observed in the periventricular preoptic nucleus and in the
dorsal rhombencephalon. In 1 month 2 months old animals, VIP-like immunoreactive elements were confined to the olfactory organ, the olfactory bulbs, the periventricular preoptic nucleus and the pituitary, pars distalis. At 3 months stage, a large number of cells was
observed in the periventricular preoptic nucleus. Western immunoblot analysis confirmed that VIP-like peptides, with molecular weight similar to that of synthetic VIP, are present early during the development of zebrafish. These results show that VIP-like immunoreactive
structures appear early during ontogeny both in the olfactory pit, retina and brain. Transient expression of positive cells was found in the retina, telencephalon, diencephalon and brainstem. The location of VIP-like immunoreactivity indicates that, during development, VIP
could be involved in several neuromodulatory functions, including the processing of visual and olfactory informations, as well as growth or survival promotion activities. The presence of VIP-like immunopositive cells in the pituitary, pars distalis, suggest that, during
development, VIP may influence the secretion of pituitary hormones.
2001 Elsevier Science B.V. All rights reserved.
Keywords : Vasoactive intestinal peptide; Development; Brain; Immunohistochemistry; Zebrafish; Danio rerio
1. Introduction [8–11,33,56,57]. In rat, inhibition of VIP functions during
the postnatal period produces retardation in the appearance Vasoactive intestinal peptide VIP, is a 28 amino acid
of several complex motor behaviours [31]. Administration peptide originally isolated from the porcine gastrointestinal
of a VIP antagonist to pregnant mice resulted in mi- tract [61]. Subsequently, VIP immunoreactivity and VIP
crocephaly in the newborn [29], and in sympathetic and mRNA were found in several neuronal populations in the
neuroblastoma cultures, VIP stimulates neuronal mitosis, brain of rat [4,13,16,18,23,44,46,62], mouse [46,62], cat
neurite extention and neuronal survival [56,57]. Studies of [55], hedgehog and sheep [2], swine [20], and man
mouse early embryo have demonstrated that VIP is present [17,6,67]. In the brain, in addition to exhibiting neuro-
in high concentrations in developing nervous system at modulator and neurotransmitter functions [27], VIP has
critical period of cell proliferation and differentiation [33]. been shown to have growth and survival-promoting actions
All these observations indicate that VIP is an important developmental regulator in mammals.
In nonmammalian species, the presence of VIP in the
Corresponding author. Tel.: 139-10-353-8050; fax: 139-10-353-
brain has been described in detail only in adult quail
8047. E-mail address
: mvallariunige.it M. Mathieu.
[3,70], pigeon [54] and chick [41,42]. In fish, VIP has been
0006-8993 01 – see front matter
2001 Elsevier Science B.V. All rights reserved. P I I : S 0 0 0 6 - 8 9 9 3 0 0 0 3 0 6 5 - 1
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demonstrated in the brain of several species of teleosts, represents a simple model characterized by well defined
including tilapia [38], sea bream [58], green molly [5], developmental stages and it is one of the major models for
salmon, trout and carp [12]. To our knowledge, there are the genetic study of early brain development.
no studies on the ontogeny of VIP in the brain of fishes, in spite of developmental models notably different with
respect to: i mother embryo relationships; ii presence