Neurochemical Research

, Volume 19, Issue 7, pp 845–850 | Cite as

In vitro TRH release from hypothalamus slices varies during the diurnal cycle

  • L. Covarrubias
  • J. L. Redondo
  • M. A. Vargas
  • R. M. Uribe
  • M. Méndez
  • P. Joseph-Bravo
  • J. L. Charli
Original Articles

Abstract

We have previously described a daily rhythm in thyrotropin releasing hormone (TRH) and TRH mRNA in the rat hypothalamus. To determine whether TRH release fluctuates in a diurnal manner, we have measured basal and potassium stimulated release from hypothalamic slices, and compared it to release from olfactory bulb slices, during the diurnal cycle. Basal TRH release was higher at 7:00 h than at any other time (1:00, 13:00 or 19:00 h) in either hypothalamus or olfactory bulb. The ratio of stimulated over basal release was higher in the hypothalamus at 19:00 h, when TRH content was highest. Potassium stimulated TRH release from olfactory bulb was not different from basal release at any time. TRH release fluctuations were not due to a rhythm of extracellular inactivation: the activity of pyroglutamyl aminopeptidase II, an ectoenzyme responsible for TRH inactivation, was constant throughout the cycle. Our data demonstrate that diurnal variations of TRH release occur in vitro and that the enhanced responsiveness to potassium stimulation in hypothalamus is correlated with increased levels of peptide.

Key Words

Thyrotropin releasing hormone hypothalamus olfactory bulb in vitro release circadian cycle 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Levine, J. E., and Ramirez, V. D. 1989. Measurement of neuropeptide release: in vitro and in vivo procedures. Pages 163–192.in Conn, P. M. (ed.) Neuroendocrine peptide methodology. Academic Press, Inc., San Diego.Google Scholar
  2. 2.
    Kendrick, K. M. 1989. Use of microdialysis in neuroendocrinology. Pages 229–252,in Conn, P. M. (ed.) Neuroendocrine peptide methodology. Academic Press, Inc., San Diego.Google Scholar
  3. 3.
    Robbins, R., and Reichlin, S. 1982. In vitro systems for the study of secretion and synthesis of hypothalamic peptides. Pages 111–135.in Muller, E. E. and MacLeod, R. M. (eds.) Neuroendocrine perspectives, vol. 1. Elseviet Biomedical Press, Amsterdam.Google Scholar
  4. 4.
    Drouva, S. V., Laplante, E. and Kordon, C. 1985. Progesterone-induced LHRH release in vitro is an estrogen- as well as Ca2+-and calmodulin-dependent secretory process. Neuroendocrinology. 40:325–331.PubMedGoogle Scholar
  5. 5.
    Levine, J. E., and Ramirez, V. D. 1980. In vivo release of luteinizing hormone-releasing hormone estimated with push-pull cannulae from the mediobasal hypothalami of ovariectomized, steroid-primed rats. Endocrinology. 107:1782–1790.PubMedGoogle Scholar
  6. 6.
    Ramirez, V. D., Dluzen, D., and Lin, D. 1980. Progesterone administration in vivo, stimulates release of luteinizing hormone-releasing hormone in vitro. Science. 208:1037–1039.PubMedGoogle Scholar
  7. 7.
    Lechan, R. M., and Toni, R. 1992. Thyrotropin releasing hormone neuronal systems in the central nervous system. Pages 279–330.in Nemeroff, C. B. (ed.), Neuroendocrinology, CRC Press, Boca Raton.Google Scholar
  8. 8.
    Rondeel, J. M. M., De Greef, W. J., Klootwijk, W., and Visser, T. J. 1992. Effects of hypothyroidism on hypothalamic release of thyrotropin releasing hormone in rats. Endocrinology. 130:651–656.PubMedGoogle Scholar
  9. 8.
    Arancibia, S., Tapia-Arancibia, L., Assenmacher, I., and Astier, H. 1983. Direct evidence of short-term cold-induced TRH release in the median eminence of unanesthetized rats. Neuroendocrinology. 37:225–228.PubMedGoogle Scholar
  10. 10.
    De Greef, W. J., and Visser, T. J. 1981. Evidence for the involvement of hypothalamic dopamine and thyrotropin releasing hormone in suckling-induced release of prolactin. Journal of Endocrinology. 91:213–223.PubMedGoogle Scholar
  11. 11.
    Segerson, T. P., Kauer, J., Wolfe, H. C., Mobtaker, H., Wu, P., Jackson, I. M. D., and Lechan, R. M. 1987. Thyroid hormone regulates TRH biosynthesis in the paraventricular nucleus of the rat hypothalamus. Science. 238:78–80.PubMedGoogle Scholar
  12. 12.
    Uribe, R. M., Redondo, J. L., Charli, J. L., and Joseph-Bravo, P. 1983. Suckling and cold stress rapidly and transiently increase TRH mRNA in the paraventricular nucleus. Neuroendocrinology. 58:140–145.Google Scholar
  13. 13.
    Covarrubias, L., Uribe, R. M., Méndez, M., Charli, J. L., and Joseph-Bravo, P. 1988. Neuronal TRH synthesis: developmental and circadian TRH mRNA levels. Biochemical Biophysical Research Communications. 151:615–622.Google Scholar
  14. 14.
    Millington, W. R., Blum, M., Knight, R., Mueller, G. P., Roberts, J. L., and O'Donohue, T. L. 1986. A diurnal rhythm in proopiomelanocortin messenger ribonucleic acid that varies concomitantly with the content and secretion of β-endorphin in the intermediate lobe of the rat pituitary. Endocrinology. 118:829–834.PubMedGoogle Scholar
  15. 15.
    Watts, A. G., and Swanson, L. W. 1989. Diurnal variations in the content of preprocorticotropin-releasing hormone messenger ribonucleic acid in the hypothalamic paraventricular nucleus of rats of both sexes as measured by in situ hybridization. Endocrinology. 125:1734–1738.PubMedGoogle Scholar
  16. 16.
    Ulh, G. R., and Reppert, S. M. 1986. Suprachiasmatic nucleus vasopressin messenger RNA: circadian variation in normal and Brattelboro rats. Science. 232:390–393.PubMedGoogle Scholar
  17. 17.
    Méndez, M., Joseph-Bravo, P., Cisneros, M., Vargas, M. A., and Charli, J. L. 1987. Regional distribution of in vitro release of thyrotropin releasing hormone in rat brain. Peptides. 8:291–298.PubMedGoogle Scholar
  18. 18.
    Charli, J. L., Cruz, C., Vargas, M. A., and Joseph-Bravo, P. 1988. The narrow specificity pyroglutamate amino peptidase degrading TRH in rat brain is an ectoenzyme. Neurochemistry International. 13:237–242.Google Scholar
  19. 19.
    Charli, J. L., Méndez, M., Vargas, M. A., Cisneros, M., Assai, M., Joseph-Bravo, P., and Wilk, S. 1989. Pyroglutamyl peptidase II inhibition specifically increases recovery of TRH released from rat brain slices. Neuropeptides. 14:191–196.PubMedGoogle Scholar
  20. 20.
    Vargas, M. A., Méndez, M., Cisneros, M., Joseph-Bravo, P., and Charli, J. L. 1987. Regional distribution of the membrane bound pyroglutamate aminopeptidase degrading thyrotropin releasing hormone in rat brain. Neuroscience Letters. 79:311–314.PubMedGoogle Scholar
  21. 21.
    Tapia-Arancibia, L., and Astier, H. 1983. Opiate inhibition of K+-induced TRH release from superfused mediobasal hypothalami in rats. Neuroendocrinology. 37:166–168.PubMedGoogle Scholar
  22. 22.
    Tapia-Arancibia, L., Arancibia, S., and Astier, H. 1984. K+-induced thyrotropin-releasing hromone release from superfused mediobasal hypothalami in rat. Inhibition by somatostatin. Neuroscience Letters. 45:57–52.Google Scholar
  23. 23.
    Burns, G., Brown, B. L., and Dobson, P. R. M. 1988. Diurnal variation in the effect of potassium depolarization on vasoactive intestinal polypeptide release from rat hypothalamus: a possible role for adrenaline. Journal of Endocrinology. 116:335–341.PubMedGoogle Scholar

Copyright information

© Plenum Publishing Corporation 1994

Authors and Affiliations

  • L. Covarrubias
    • 1
  • J. L. Redondo
    • 1
  • M. A. Vargas
    • 1
  • R. M. Uribe
    • 1
  • M. Méndez
    • 1
  • P. Joseph-Bravo
    • 1
  • J. L. Charli
    • 1
  1. 1.Instituto de BiotecnologiaUniversidad Nacional Autonoma de MexicoCuernavacaMexico
  2. 2.U339 INSERMHôpital Saint-AntoineParisFrance

Personalised recommendations