Melatonin induces the expression of gonadotropin-inhibitory hormone in the avian brain - PubMed (original) (raw)

Melatonin induces the expression of gonadotropin-inhibitory hormone in the avian brain

Takayoshi Ubuka et al. Proc Natl Acad Sci U S A. 2005.

Abstract

We recently identified a novel hypothalamic neuropeptide inhibiting gonadotropin release in quail and termed it gonadotropin-inhibitory hormone (GnIH). Cell bodies and terminals containing the dodecapeptide GnIH are localized in the paraventricular nucleus (PVN) and median eminence, respectively. To understand the physiological role of GnIH, we investigated the mechanisms that regulate GnIH expression. In this study, we show that melatonin originating from the pineal gland and eyes induces GnIH expression in the quail brain. Pinealectomy (Px) combined with orbital enucleation (Ex) (Px plus Ex) decreased the expression of GnIH precursor mRNA and content of mature GnIH peptide in the diencephalon, which includes the PVN and median eminence. Melatonin administration to Px plus Ex birds caused a dose-dependent increase in expression of GnIH precursor mRNA and production of mature peptide. The expression of GnIH was photoperiodically controlled and increased under short-day photoperiods, when the duration of melatonin secretion increases. To identify the mode of melatonin action on GnIH induction, we investigated the expression of Mel(1c), a melatonin receptor subtype, in GnIH neurons. In situ hybridization of Mel(1c) mRNA combined with immunocytochemistry for GnIH revealed that Mel(1c) mRNA was expressed in GnIH-immunoreactive neurons in the PVN. Melatonin receptor autoradiography further revealed specific binding of melatonin in the PVN. These results indicate that melatonin is a key factor for GnIH induction. Melatonin appears to act directly on GnIH neurons through its receptor to induce GnIH expression. This is the first demonstration, to our knowledge, of a direct action of melatonin on neuropeptide induction in any vertebrate class.

PubMed Disclaimer

Figures

Fig. 1.

Fig. 1.

Effects of Px and Px combined with Ex (Px+Ex) on the expressions of GnIH precursor mRNA level (A) and GnIH (B) in the diencephalon and melatonin concentrations in the diencephalon (C) and plasma (D). Each column and the vertical line represent the mean ± SEM (n = 5 samples; one sample from one bird). **, P < 0.01 versus SH; ††, P < 0.01, †, P < 0.05 Px versus Px plus Ex by one-way ANOVA, followed by Duncan's multiple range test.

Fig. 2.

Fig. 2.

Effects of Px combined with Ex and melatonin (10 mg per plate) administration to Px plus Ex (Px + Ex) birds (Px + Ex + M) on the expressions of GnIH precursor mRNA (A–C) and GnIH (D–F) in PVN neurons. (Bars, 50 μm.)

Fig. 3.

Fig. 3.

Quantitative analyses of the expression of GnIH precursor mRNA (A) and GnIH content (B) in PVN neurons in the SH, Px plus Ex, and Px plus Ex plus melatonin birds. The immunoreactivity of individual neurons was measured as a gray scale value from 0 (white) to 256 (black) and expressed as the mean density per cell, which was obtained by subtracting background gray values. Each column and the vertical lin_e_ represent the mean ± SEM (n = 5 samples; one sample from one bird). **, P < 0.01; *, P < 0.05, SH versus Px plus Ex; ††, P < 0.01, Px plus Ex versus Px plus Ex plus melatonin by one-way ANOVA, followed by Duncan's multiple range test.

Fig. 4.

Fig. 4.

Effects of melatonin administration on the expression of GnIH precursor mRNA (A) and GnIH content (B) in the diencephalon. Various doses of melatonin (low dose: 2.5 mg per plate, medium dose: 10 mg per plate, and high dose: 40 mg per plate) were administered to Px plus Ex quail by means of a Silastic plate for 1 week (Px plus Ex plus melatonin; Px+Ex+M). Px plus Ex quail (controls) were implanted with only Silastic adhesive. Each column and the vertical line represent the mean ± SEM (n = 5 samples; one sample from one bird). **, P < 0.01; *, P < 0.05 versus Px plus Ex (control); ††, P < 0.01; †, P < 0.05 versus Px plus Ex plus melatonin (low dose) by one-way ANOVA, followed by Duncan's multiple range test.

Fig. 5.

Fig. 5.

Effect of photoperiodic manipulation on the expression of GnIH precursor mRNA (A) and GnIH content (B) in the diencephalon and combined testicular weight (C). Quail were exposed to either LD or SD photoperiods for 3 weeks. Each column and the vertical line represent the mean ± SEM (n = 8 samples; one sample from one bird). **, P < 0.01; *, P < 0.05 versus LD by Student's t test.

Fig. 6.

Fig. 6.

Expression of Mel1c mRNA in the GnIH neuron. In situ hybridization using antisense RNA probe for Mel1c mRNA in the quail PVN (A and C) was followed by immunocytochemistry for GnIH (B and D) on the same section. In situ hybridization using sense RNA probe (E) and immunocytochemistry with the GnIH antiserum preincubated with a saturating concentration of synthetic GnIH (F) served as controls. A and B are at the same low magnification. (Bars, 100 μm.) C–F are at the same high magnification. (Bars, 30 μm.) C and D are at the same high magnification of blocked areas in A and B, respectively. Arrows in C and D indicate identical cells. Similar results were obtained in repeated experiments by using six different birds.

Similar articles

Cited by

References

    1. Tsutsui, K., Saigoh, E., Ukena, K., Teranishi, H., Fujisawa, Y., Kikuchi, M., Ishii, S. & Sharp, P. J. (2000) Biochem. Biophys. Res. Commun. 275, 661-667. - PubMed
    1. Ukena, K., Ubuka, T. & Tsutsui, K. (2003) Cell Tissue Res. 312, 73-79. - PubMed
    1. Ubuka, T., Ueno, M., Ukena, K. & Tsutsui, K. (2003) J. Endocrinol. 178, 311-318. - PubMed
    1. Satake, H., Hisada., M., Kawada, T., Minakata, H., Ukena, K. & Tsutsui, K. (2001) Biochem. J. 354, 379-385. - PMC - PubMed
    1. Osugi, T., Ukena, K., Bentley, G. E., O'Brien, S., Moore, I. T., Wingfield, J. C. & Tsutsui, K. (2004) J. Endocrinol. 182, 33-42. - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources