LPXRFa peptide system in the European sea bass: A molecular and immunohistochemical approach

• Published in: Journal of comparative neurology (1911) Vol. 524; no. 1; pp. 176 - 198
• Main Authors: Paullada-Salmerón, José A., Cowan, Mairi, Aliaga-Guerrero, María, Gómez, Ana, Zanuy, Silvia, Mañanos, Evaristo, Muñoz-Cueto, José A.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.01.2016; Wiley Subscription Services, Inc
• Subjects: Amino Acid Sequence; Animals; Antibodies - metabolism; Bass - anatomy & histology; Bass - genetics; Bass - metabolism; brain; Brain - anatomy & histology; Brain - metabolism; Cloning, Molecular - methods; Dicentrarchus labrax; Female; Freshwater; GnIH; immunohistochemistry; Immunohistochemistry - methods; LPXRFamide; Male; Marine; Molecular Sequence Data; Peptide Hormones - genetics; Peptide Hormones - immunology; Peptide Hormones - metabolism; Phylogeny; Pituitary Gland - anatomy & histology; Pituitary Gland - metabolism; reproduction; RRID: AB_2493177; sea bass; Sequence Homology, Amino Acid; Teleostei; RRID: AB_2493177; sea bass; LPXRFamide; GnIH; immunohistochemistry; brain; reproduction
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.23833

Gonadotropin‐inhibitory hormone (GnIH) is a neuropeptide that suppresses reproduction in birds and mammals by inhibiting GnRH and gonadotropin secretion. GnIH orthologs with a C‐terminal LPXRFamide (LPXRFa) motif have been identified in teleost fish. Although recent work also suggests its role in fish reproduction, studies are scarce and controversial, and have mainly focused on cyprinids. In this work we cloned a full‐length cDNA encoding an LPXRFa precursor in the European sea bass, Dicentrarchus labrax. In contrast to other teleosts, the sea bass LPXRFa precursor contains only two putative RFamide peptides, termed sbLPXRFa1 and sbLPXRFa2. sblpxrfa transcripts were expressed predominantly in the olfactory bulbs/telencephalon, diencephalon, midbrain tegmentum, retina, and gonads. We also developed a specific antiserum against sbLPXRFa2, which revealed sbLPXRFa‐immunoreactive (ir) perikarya in the olfactory bulbs‐terminal nerve, ventral telencephalon, caudal preoptic area, dorsal mesencephalic tegmentum, and rostral rhombencephalon. These sbLPXRFa‐ir cells profusely innervated the preoptic area, hypothalamus, optic tectum, semicircular torus, and caudal midbrain tegmentum, but conspicuous projections also reached the olfactory bulbs, ventral/dorsal telencephalon, habenula, ventral thalamus, pretectum, rostral midbrain tegmentum, posterior tuberculum, reticular formation, and viscerosensory lobe. The retina, pineal, vascular sac, and pituitary were also targets of sbLPXRFa‐ir cells. In the pituitary, this innervation was observed close to follicle‐stimulating hormone (FSH), luteinizing hormone (LH) and growth hormone (GH) cells. Tract‐tracing retrograde labeling suggests that telencephalic and preoptic sbLPXRFa cells might represent the source of pituitary innervation. The immunohistochemical distribution of sbLPXRFa cells and fibers suggest that LPXRFa peptides might be involved in some functions as well as reproduction, such as feeding, growth, and behavior. J. Comp. Neurol. 524:176–198, 2016. © 2015 Wiley Periodicals, Inc. This is the first study employing an antibody against the endogenous amino‐acid sequence of an LPXRFa (GnIH) peptide in teleosts. This study reveals that fish GnIH cells are not restricted to the preoptic area, being also located in terminal nerve ganglion, ventral telencephalon, dorsal mesencephalic tegmentum and rostral rhombencephalon.