Abstract
Using specific radioimmunoassays for the two GnRH molecular forms present in the European eel, Anguilla anguilla, (mGnRH and cGnRH II), we compared their distributions in the pituitary and different parts of the brain of female silver eels, as well as the modifications of their levels in experimentally matured female eels (treated with carp pituitary extract). In control eels, mGnRH levels were higher than cGnRH II levels in the pituitary, olfactory lobes and telencephalon, di- and mesencephalon, while the opposite was found in the posterior part of the brain (met- and myelencephalon). Experimental sexual maturation of the gonads significantly increased mGnRH levels in the pituitary and anterior parts of the brain; such a positive effect was not observed on the low cGnRH II levels, which were, in contrast, reduced. These data indicate that the positive feedback of gonadal hormones on GnRH, that we previously demonstrated, would specifically affect the mGnRH form. The differential distribution and control of mGnRH and cGnRH II suggest that these two forms have different physiological roles in the eel. The large increase in mGnRH during sexual maturation suggests the prime implication of this form in the neuroendocrine control of reproduction.
Résumé
Au moyen de dosages radioimmunologiques spécifiques de chacune des formes de GnRH présentes chez l'anguille européenne, Anguilla anguilla, (mGnRH et cGnRH II), nous avons comparé leur répartition dans l'hypophyse et les différentes parties du cerveau, chez l'anguille femelle argentée, ainsi que les modifications de leurs teneurs chez des femelles dont la maturation sexuelle est induite par un traitement à l'extrait hypophysaire de carpe. Chez les témoins, mGnRH est plus abondant que cGnRH II dans l'hypophyse, les lobes olfactifs et le téléncéphale, le di-et mésencéphale, alors que l'inverse est observé dans la partie postérieure du cerveau (mét- et mésencéphale). La maturation expérimentale des gonades entraine une augmentation significative des teneurs en mGnRH de l'hypophyse et des parties antérieures du cerveau; un tel effet positif n'est pas observé sur les faibles teneurs en cGnRH II qui, au contraire, sont diminuées. Ces données indiquent que le rétrocontrôle positif des stéroides gonadiques sur GnRH, que nous avions démontré précédemment, s'exercerait spécifiquement sur la forme mGnRH. Les différences dans la répartition et le contrôle de mGnRH et cGnRH II suggèrent que ces deux formes ont des rôles physiologiques différents chez l'anguille. L'élévation importante de mGnRH lors de la maturation sexuelle suggère l'implication principale de cette forme dans le contrôle neuroendocrine de la fonction de reproduction.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References cited
Chang, J.P. and De Leeuw, R. 1990. In vitro goldfish growth hormone response to gonadotropin-releasing hormone: possible roles of extracellular calcium and arachidonic acid metabolism. Gen. Comp. Endocrinol. 80: 155–164.
Dufour, S., Pasqualini, C., Kerdelhué, B. and Fontaine, Y.A. 1982. Presence and distribution of radioimmunoassayable LHRH in the European eel, Anguilla anguilla. Neuropeptides 3: 159–171.
Dufour, S., Fontaine, Y.A. and Kerdelhué, B. 1985. Increase in brain and pituitary radioimmunoassayable gonadotropin releasing hormone (GnRH) in the European silver eel treated with sexual steroid or human chorionic gonadotropin. Neuropeptides 6: 495–502.
Dufour, S., Lopez, E., Le Menn, F., Le Belle, N., Baloche, S. and Fontaine, Y.A. 1988. Stimulation of gonadotropin release and of ovarian development, by the administration of a gonadoliberin agonist and of dopamine antagonists, in female silver eel pretreated with estradiol. Gen. Comp. Endocrinol. 70: 20–30.
Dufour, S., Le Belle, N., Baloche, S. and Fontaine, Y.A. 1989. Positive feedback control by the gonads on gonadotropin (GTH) and gonadoliberin (GnRH) levels in experimentally matured female silver eels, Anguilla anguilla. Fish Physiol. Biochem. 7: 157–162.
Dufour, S., Bassompierre, M., Montero, M., Le Belle, N., Baloche, S. and Fontaine, Y.A. 1991. Stimulation of pituitary gonadotropic function in female silver eels treated by a gonadoliberin agonist and dopamine antagonists. In: Proc. IVth Int. Symp. Reproductive Physiology of Fish. pp. 54–56. Edited by A.P. Scott, J.P. Sumpter, D.E. Kime and M.S. Rolfe. FishSymp 91, Sheffield.
Fontaine, M., Bertrand, E., Lopez, E. and Callamand, O. 1964. Sur la stimulation des organes génitaux de l'anguille femelle (Anguilla anguilla L.) et l'émission spontanée des oeufs en aquarium. C.R. Acad. Sci., Paris, 259: 2907–2910.
Goos, H.J.Th., De Leeuw, R., Cook, H. and Van Oordt P.G.W.J. 1986. Gonadotropic hormone-releasing hormone (GnRH) bioactivity in the brain of immature rainbow trout, Salmo gairdneri: the effect of testosterone. Gen. Comp. Endocrinol. 64: 80–84.
Kah, O., Dufour, S., Baloche, S. and Breton, B. 1989. The GnRH systems in the brain and pituitary of normal and hCG treated European silver eels. Fish Physiol. Biochem. 6: 279–284.
Kalra, P.S. 1985. Stimulation of hypothalamic LHRH levels and release by gonadal steroids. J. Ster. Biochem. 23: 725–731.
Katz, I.A., Millar, R.P. and King, J.A. 1990. Differential regional distribution and release of two forms of gonadotropin-releasing hormone in the chicken brain. Peptides 11: 443–450.
King, J.A., Dufour, S., Fontaine, Y.A. and Millar, R.P. 1990. Chromatographic and immunological evidence for mammalian GnRH and chicken II GnRH in eel (Anguilla anguilla) brain and pituitary. Peptides 11: 507–514.
Marchant, T.A., Chang, J.P., Nahorniak, C.S. and Peter, R.E. 1989. Evidence that gonadotropin-releasing hormone also functions as a growth hormone-releasing factor in the goldfish. Endocrinology 124: 2509–2518.
Melrose, P. and Gross, L. 1987. Steroid effects on the secretory modalities of gonadotropin-releasing hormone release. Endocrinology 121: 190–199.
Mikami, S.-I., Yamada, S., Hasegawa, Y. and Miyamoto, K. 1988. Localization of avain LHRH-immunoreactive neurons in the hypothalamus of the domestic fowl, Gallus domesticus, and the Japanese guail, Coturnix coturnix. Cell Tiss. Res. 251: 51–58.
Millam, J.R., Craig-Veit, C.B., Adams, T.E. and Adams, B.M. 1989. Avian gonadotropin-releasing hormones I and II in brain and other tissues in turkey hens. Comp. Biochem. Biophys. 94A: 771–776.
Millar, R.P. and King, J.A. 1988. Evolution of gonadotropin-releasing hormone: multiple usage of a peptide. News Physiol. Sci. 3: 49–53.
Okuzawa, K., Amano, M., Kobayashi, M., Aida, K., Hanyu, I., Hasegawa, Y., and Myamoto, K. 1988. Differences in salmon GnRH and chicken GnRH-II contents in discrete brain areas of male and female rainbow trout according to age and sexual maturity. Gen. Comp. Endocrinol. 80: 116–126.
Quérat, B., Hardy, A. and Fontaine, Y.A. 1991. Regulation of the type-II gonadotropin α and β subunit mRNAs by oestradiol and testosterone in the European eel. J. Mol. Endocrinol. 7: 81-86.
Radovick, S., Ticknor, C.M., Nakayama, Y., Notides, A.C., Rahman, A., Weintraub, B.D., Cutler, G.B., Jr. and Wondisford, F.E. 1991. Evidence for direct estrogen regulation of the human gonadotropin-releasing hormone gene. J. Clin. Invest. 88: 1646–1655.
Rothfeld, J., Hejtmancik, J.F., Conn, P.M., and Pfaff, D.W. 1989. In situ hybridization for LHRH mRNA following estrogen treatment. Mol. Brain Res. 6: 121–125.
Salacinski, P.R.P., McLean, C., Sykes, J.E.C., Clement-Jones, U.U. and Lowry, P.J. 1981. Iodination of proteins, glycoproteins, and peptides using solid-phase oxydating agent, 1,3,4,6-tetrachloro-3-6 diphenyl glycouryl (lodogen). Anal. Biochem. 117: 136–146.
Sharp, P.J., Talbot, R.T., Main, G.M., Dunn, I.C., Fraser, H.M. and Huskisson, N.S. 1990. Physiological roles of chicken LHRH-I and -II in the control of gonadotrophin release in the domestic chicken. J. Endocrinol. 124: 291–299.
Sherwood, N.M. 1987. The GnRH family of peptides. Trends Neurosci. 10: 129–132.
Sherwood, N.M., Eiden, L., Brownstein, M., Spiess, J., Rivier, J. and Vale, W. 1983. Characterization of a teleost gonadotropin-releasing hormone. Proc. Nat. Acad. Sci. U.S.A. 80: 2794–2798.
Schreibman, M.P., Margolis-Nunno, H., Halpern-Sebold, L., Goos, H.J.Th. and Perlman, P.W. 1986. The influence of androgen administration on the structure and function of the brain-pituitary-gonad axis of sexually immature platyfish, Xiphophorus maculatus. Cell Tiss. Res. 245: 519–524.
Toranzo, D., Dupont, E., Simard, J., Labrie, C., Couet, J., Labrie, F. and Pelletier, G. 1989. Regulation of progonadotropin-releasing hormone gene expression by sex steroids in the brain of male and female rats. Mol. Endocrinol. 3: 1748–1756.
Wilson, S.C., Gladwell, R.T. and Cunningham, F.J. 1990. Differential responses of hypothalamic LHRH-I and -II to castration and gonadal steroid or tamoxifen treatment in cockerels. J. Endocrinol. 125: 139–146.
Yu, K.L., Sherwood, N.M. and Peter, R.E. 1988. Differential distribution of two molecular forms of gonadotropin-releasing hormone in discrete brain areas of goldfish (Carassius auratus). Peptides 9: 625–630.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Dufour, S., Montero, M., Le Belle, N. et al. Differential distribution and response to experimental sexual maturation of two forms of brain gonadotropin-releasing hormone (GnRH) in the European eel, Anguilla anguilla . Fish Physiol Biochem 11, 99–106 (1993). https://doi.org/10.1007/BF00004555
Issue Date:
DOI: https://doi.org/10.1007/BF00004555