Distribution of growth hormone‐releasing hormone‐like peptide: Immunoreactivity in the central nervous system of the adult zebrafish (Danio rerio)

Abstract

The distribution of growth hormone-releasing hormone-like peptides (GHRH-LP) in the central nervous system of the zebrafish was investigated by using immunohistochemical techniques with polyclonal antibodies. ELISAs showed that the antiserum raised against salmon (s)GHRH-LP recognized both zebrafish GHRH-LP1 and -2, whereas the antiserum raised against carp (c)GHRH-LP was more sensitive but detected only zebrafish GHRH-LP1. Neither antiserum detected the true GHRH. Large cells in the nucleus lateralis tuberis were immunoreactive with both antisera, which suggests that they contained zebrafish GHRH-LP1, but not excluding GHRH-LP2. Also, immunoreactive fibers, which putatively originated from these hypothalamic neurons, were present in the hypophysis; both antisera detected fibers, although only sGHRH-LP antiserum stained fibers in the neurointermediate lobe. These fibers may have a neuroendocrine role. Candidates for a role in feeding include several areas in which both antisera labeled cells and fibers, implying a strong reaction for GHRH-LP1 and possibly GHRH-LP2. These areas include the isthmus with cells in the secondary gustatory/visceral nucleus, which were also calretinin immunoreactive. Numerous GHRH-LP-immunoreactive fibers (also labeled by both antisera) probably originate from the gustatory/visceral nucleus to innervate the ventral area of the telencephalon, preglomerular nuclei, torus lateralis and hypothalamic diffuse nucleus, habenula, torus semicircularis, and dorsolateral funiculus of the spinal cord. Present results in the zebrafish brain suggest involvement of GHRH-LP in both neuroendocrine and feeding-associated nervous circuits. The present data on the location of the two GHRH-LPs are the first clue to the possible functions of these two hormones.

The Brain of the Archerfish Toxotes chatareus: A Nissl-Based Neuroanatomical Atlas and Catecholaminergic/Cholinergic Systems

“…The emergence of the ventral periventricular hypothalamus (Hv) is observed ventral to the horizontal commissure (chor). A conspicuous large-celled laterally lying nucleus is present at these levels in the archerfish hypothalamus which likely corresponds to the neuroendocrine lateral tuberal nucleus (NLT) seen in other teleosts where it expresses various neuropeptides (Cerda-Reverter et al, 2001b; Huesa et al, 2005; Castro et al, 2009). …”

Enhancer turnover and conserved regulatory function in vertebrate evolution

“…The mammalian arcuate nucleus and the teleost NLT are generally considered to be homologous anatomical structures since they are both located in the ventromedial hypothalamus and express a highly similar gene set, such as agouti-related peptide (agrp) [64,77,78], somatostatin (sst) [79], growth hormone releasing hormone (ghrh) [80], the leptin receptor (lepr) [81] and Pomc [51,64]. The NLT and the arcuate also show conserved function.…”

Evidence of a reproduction-related function for pituitary adenylate cyclase-activating polypeptide-related peptide in an Anabantidae fish

“…In Salmonidae (chum salmon and coho salmon), ir-PRP was identified at the terminal nerve ganglion system, associated with the olfactory nerve and superficial basal regions of the olfactory bulbs (Parker & Sherwood 1990), and fibers containing ir-PRP have been found in the proximal pars distalis in the vicinity of the somatotrophs in several teleost species (Olivereau et al 1990, Rao et al 1996. The physiological relevance of PRP as a hypophysiotropic factor has been further confirmed by the identification of a specific high affinity G-proteincoupled receptor (GPCR) of PRP in the goldfish and zebrafish pituitary (Castro et al 2009). Binding PRP to this receptor can elicit a cAMP increase in PRP receptor-transfected cells, indicating that PRP may exert biological activities through a specific receptor.…”

“…Antiserum, directed against PRP, reacts with the pituitary in the pars distalis cell bodies and with neuronal cell bodies in the hypothalamus that project axonal pathways toward the median eminence and terminate primarily in the pars nervosa in Gadus morhua (Pan et al 1985) and rainbow trout (Luo & McKeown 1989). In addition, in the zebrafish, ir-PRP recognized fibers that probably originated from the gustatory/visceral nucleus and innervated the ventral area of the telencephalon, hypothalamus, and the spinal cord (Castro et al 2009). In Salmonidae (chum salmon and coho salmon), ir-PRP was identified at the terminal nerve ganglion system, associated with the olfactory nerve and superficial basal regions of the olfactory bulbs (Parker & Sherwood 1990), and fibers containing ir-PRP have been found in the proximal pars distalis in the vicinity of the somatotrophs in several teleost species (Olivereau et al 1990, Rao et al 1996.…”