Skip to main content
NCBI home page
Cellular and Molecular Neurobiology logoLink to Cellular and Molecular Neurobiology
. 1995 Feb;15(1):89–106. doi: 10.1007/BF02069560

Dynamic alterations in luteinizing hormone-releasing hormone (LHRH) neuronal cell bodies and terminals of adult rats

J C King 1,✉, B S Rubin 1
PMCID: PMC11563131  PMID: 7648612

Abstract

1. The decapeptide lueteinizing hormone-releasing hormone (LHRH) is synthesized in neuronal cell bodies diffusely distributed across the basal forebrain and is secreted from neuronal terminals in the median eminence. Once secreted, LHRH enters the portal vessels and is then transported to the anterior pituitary, where it modulates the synthesis and secretion of gonadotropins, which are essential to gonadal function and reproduction.

2. Because of the difficulties encountered in studying these diffusely distributed neurons, we have developed strategies which combine immunocytochemistry and computer-assisted techniques to examine individual LHRH neuronal cell bodies, as well as the entire population of LHRH neurons from the diagonal band of Broca to the mammillary bodies. In addition, we have examined LHRH neuronal terminals in the median eminence using computer-assisted imaging techniques to examine individual terminals by electron microscopy or across all rostral-caudal regions of the median eminence by light microscopy. In our most recent studies using confocal microscopy, we have examined the relationships of LHRH terminals to glial processes.

3. These studies reveal a very dynamic system of LHRH neuronal cell bodies and terminals. The population of neurons in which LHRH can be detected varies as a function of time after gonadectomy, during the estrous cycle, and during the preovulatory surge of LH during the afternoon of proestrus. Dynamic changes are also observed in LHRH terminals in the median eminence as a function of time after gonadectomy and in specific rostral-caudal regions of the median eminence during the preovulatory surge of LH. Finally, confocal microscopy reveals that LHRH terminals are prevented from contacting the basal lamina of the brain by glial end-feet.

4. We are currently examining the hypothesis that these relationships change as a function of endocrine milieu and, therefore, participate in the modulation of LHRH secretion. Ongoing studies focus on defining the sites of action and synergy of multiple sources of regulation of LHRH secretion and their relative importance to ensuring reproductive success.

Key words: median eminence, luteinizing hormone-releasing hormone, gonadotropin-releasing hormone, hypothalamus, luteinizing hormone, gonadectomy

References

  1. Brownstein, M. J., Russell, J. T., and Gainer, H. (1980). Synthesis, transport, and release of posterior pituitary hormones.Science207:373–378. [DOI] [PubMed] [Google Scholar]
  2. Christiansen, H., Stephenson, M., Nay, B., and Grimsrud, A. (1987).Movie. BYU Training Text, Graphics Utah Style, Provo. [Google Scholar]
  3. Hiatt, E. S., Brunetta, P. G., Seiler, G. R.,et al. (1992). Subgroups of luteinizing hormone-releasing hormone perikarya defined by computer analyses in the basal forebrain of intact female rats.Endocrinology130:1030–1043. [DOI] [PubMed] [Google Scholar]
  4. Hoffman, G. E., Lee, W. S., Attardi, B., Yann, V., and Fitzimmons, M. D. (1990). Luteinizing hormone-releasing hormone neurons express c-fos antigen after steroid activation.Endocrinology126:1736–1741. [DOI] [PubMed] [Google Scholar]
  5. Hunter, D. D., Porter, B. E., Bullock, J. W., Adams, S. P., Merlie, J. P., and Sanes, J. R. (1989). Primary sequence of a motor neuron-selective adhesive site in the synaptic basal lamina protein S-laminin.Cell59:905–913. [DOI] [PubMed] [Google Scholar]
  6. King, J. C., and Anthony, E. L. (1983). Biosynthesis of LHRH: inferences from immunocytochemical studies.Peptides4:963–970. [DOI] [PubMed] [Google Scholar]
  7. King, J. C., and Letourneau, R. J. (1994). Luteinizing hormone-releasing hormone terminals in the median eminence of rats undergo dramatic changes after gonadectomy, as revealed by electron microscopic image analysis.Endocrinology134:1340–1351. [DOI] [PubMed] [Google Scholar]
  8. King, J. C., and Rubin, B. S. (1992). GnRH subgroups: a microarchitecture. InSymposium on Modes of Action of GnRH and GnRH Analogs (P. M. Conn and Crowley, W. F. Jr. Eds.), Serono Symposia, Boston, pp. 161–178.
  9. King, J. C., and Seiler, G. R. (1988). Ultrastructural evidence suggests variations in biosynthesis and processing within LH-RH neurons as a function of ovariectomy in rats.Brain Res.452:127–140. [DOI] [PubMed] [Google Scholar]
  10. King, J. C., Tobet, S. A., Snavely, F. L., and Arimura, A. A. (1982). LHRH immunopositive cells and their projections to the median eminence and organum vasculosum of the lamina terminalis.J. Comp. Neurol.209:287–300. [DOI] [PubMed] [Google Scholar]
  11. King, J. C., Lechan, R. M., Kugel, G., and Anthony, E. L. (1983). Acrolein: A fixative for immunocytochemical localization of peotides in the central nervous system.J. Histochem. Cytochem.31:62–68. [DOI] [PubMed] [Google Scholar]
  12. King, J. C., Anthony, E. L., Damassa, D. A., and Elkind Hirsch, K. E. (1987a). Morphological evidence that luteinizing hormone-releasing hormone neurons participate in the suppression by estradiol of pituitary luteinizing hormone secretion in ovariectomized rats.Neuroendocrinology (in press). [DOI] [PubMed]
  13. King, J. C., Kugel, G., Zahniser, D., Wooledge, K., Damassa, D. A., and Alexsavich, B. (1987b). Changes in populations of LHRH-immunopositive cell bodies following gonadectomy.Peptides8:721–735. [DOI] [PubMed] [Google Scholar]
  14. Koenig, J. F. R., and Klippel, R. A. (1970).The Rat Brain: A Stereotaxic Atlas of the Forebrain and Lower Parts of the Brain Stem, R. K. Krieger, Huntington, NY. [Google Scholar]
  15. Lee, W.-S., Smith, M. S., and Hoffman, G. E. (1990). Luteinizing hormone-releasing hormone neurons express Fos protein during the proestrous surge of luteinizing hormone.Proc. Natl. Acad. Sci. USA87:5163–5167. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lee, W.-S., Abbud, R., Smith, M. S., and Hoffman, G. E. (1992a). LHRH neurons express cJun protein during the proestrous surge of luteinizing.Endocrinology130:3101–3103. [DOI] [PubMed] [Google Scholar]
  17. Lee, W.-S., Smith, M. S., and Hoffman, G. E. (1992b). cFos activity identifies recruitment of luteinizing hormone-releasing hormone neurons during the ascending phase of the proestrous luteinizing hormone surge.J. Neuroendocrinol.4:161–166. [DOI] [PubMed] [Google Scholar]
  18. Merchenthaler, I., Lopez, F. J., and Negro-Vilar, A. (1990). Colocalization of galanin and luteinizing hormone-releasing hormone in a subset of preoptic hypothalamic neurons: Anatomical and functional correlates.Proc. Natl. Acad. Sci. USA87:6326–6330. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Rubin, B. S. and King, J. C. (1995)Neuroendocrinology (in press). [DOI] [PubMed]
  20. Rubin, B. S., and King, J. C. (1994). The number and distribution of detectable luteinizing hormone (LH)-releasing hormone cell bodies changes in association with the preovulatory LH surge in the brains of young but not middle-aged female rats.Endocrinology134:467–474. [DOI] [PubMed] [Google Scholar]
  21. Rubin, B. S., King, J. C., Millar, R. P., Seeburg, P. H., and Arimura, A. (1987). Processing of luteinizing hormone-releasing hormone precursor in rat neurons.Endocrinology121:305–309. [DOI] [PubMed] [Google Scholar]
  22. Rubin, B. S., Lee, C. E., and King, J. C. (1994). A reduced proportion of luteinizing hormone (LH)-releasing hormone neurons express Fos protein during the prevulatory or steroid-induced LH surge in middle-aged rats.Biol. Reprod.51:1264–1272. [DOI] [PubMed] [Google Scholar]
  23. Seiler, G. R., Brunetta, P. G., and King, J. C. (1988). Subcellular features of LHRH neurons in cycling female rats.Soc. Neurosci. Abstr.14.
  24. Silverman, A. J., Witkin, J. W., Silverman, R. C., and Gibson, M. J., (1990). Modulation of gonadotropin-releasing hormone neuronal activity as evidenced by uptake of fluorogold from the vasculature.Synapse6:154–160. [DOI] [PubMed] [Google Scholar]
  25. Sternberger, L. A. (1986).Immunocytochemistry, Ed. 3 John Wiley & Sons, New York, pp. 168–171. [Google Scholar]
  26. Witkin, J. W., Paden, C. M., and Silverman, A. J. (1982). The luteinizing hormone-releasing hormone (LHRH) systems in the rat brain.Neuroendocrinology35:429–438. [DOI] [PubMed] [Google Scholar]
  27. Witkin, J. W., Ferin, M., Popilskis, S. J., and Silverman, A. J. (1991). Effects of gonadal steroids on the ultrastructure of GnRH neurons in the rhesus monkey: Synaptic input and glial apposition.Endocrinology129:1083–1092. [DOI] [PubMed] [Google Scholar]

Articles from Cellular and Molecular Neurobiology are provided here courtesy of Springer

RESOURCES