Experimental Brain Research

, Volume 63, Issue 3, pp 495–504 | Cite as

Immunoelectron microscopic observations of hypothalamic TRH-containing neurons in rats

  • S. Hisano
  • H. Ishizuka
  • T. Nishiyama
  • Y. Tsuruo
  • S. Katoh
  • S. Daikoku


Immunoreactive TRH-containing neurons and their synaptic associations were studied electron microscopically in the paraventricular nucleus (PVN) and dorsomedial nucleus (DMH) of the rat hypothalamus. In propylthiouracil (PTU)-treated rats, the immunoreactive cell bodies in the PVN appeared to be activated, showing a hypertrophic perikaryon, well developed Golgi bodies and numerous secretory granules. No such alterations were evident in the TRH neurons in the DMH. These findings suggest that the PVN-TRH neurons are involved in the hypothalamic-hypophysial-thyroid axis. Further, it was shown that unlabeled nerve terminals containing small and large clear vesicles make synaptic contacts with the TRH perikarya in the PVN. Thus it is likely that PVN-TRH neurons are regulated both by thyroid hormones and by other neuronal signals. In the DMH, unlabeled nerve terminals containing small and large clear vesicles, and immunoreactive terminals form synapses with TRH neurons. Thus the DMH-TRH neurons may be under dual neuronal control. It was further noted that in the DMH and PVN, TRH nerve terminals make synaptic contacts with other unlabeled neurons. It is evident that TRH acts as a neurotransmitter or neuromodulator, although the origin of TRH terminals should be elucidated.

Key words

TRH-neurons Immunoelectron microscopy Synapse Hypothalamus Rat 


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  1. Aizawa T, Greer MA (1981) Delineation of the hypothalamic area controlling thyrotropin secretion in the rat. Endocrinology 109: 1731–1738Google Scholar
  2. Aronin N, DiFiglia M, Liotta AS, Martin JB (1981) Ultrastructural localization and biochemical features of immunoreactive leu-enkephalin in monkey dorsal horn. J Neurosci 1: 561–577Google Scholar
  3. Bassiri RM, Utiger RD (1972) The preparation and specificity of antibody to thyrotropin releasing hormone. Endocrinology 90: 722–727Google Scholar
  4. Braitman DJ, Auker CR, Carpenter DO (1980) Thyrotropin-releasing hormone has multiple actions in cortex. Brain Res 194: 244–248Google Scholar
  5. Brown M, Rivier J, Vale W (1977) Actions of bombesin, thyrotropin releasing factor, prostaglandin E2 and naloxone on thermoregulation in the rat. Life Sci 20: 1681–1688Google Scholar
  6. Brownstein MJ, Palkovits M, Saavedra JM, Bassiri RM, Utiger RD (1974) Thyrotropin-releasing hormone in specific nuclei of rat brain. Science 185: 267–269Google Scholar
  7. Brownstein MJ, Eskay RL, Palkovits M (1982) Thyrotropin releasing hormone in the median eminence is in processes of paraventricular nucleus neurons. Neuropeptides 2: 197–201Google Scholar
  8. Chen HJ, Meites J (1975) Effects of biogenic amines and TRH on release of prolactin and TSH in the rat. Endocrinology 96: 10–14Google Scholar
  9. Faivre-Bauman A, Nemeskeri A, Tougard C, Tixier-Vidal A (1980) Immunological evidence for thyroliberin (TRH) neurons in primary cultures of fetal mouse brain cells. Ontogenic aspects. Brain Res 185: 289–304Google Scholar
  10. Grimm Y, Reichlin S (1973) Thyrotropin-releasing hormone (TRH): neurotransmitter regulation of secretion by mouse hypothalamic tissue in vitro. Endocrinology 93: 626–631Google Scholar
  11. Hisano S, Kawano H, Maki Y, Daikoku S (1981) Electron microscopic study of immunoreactive LHRH perikarya with special reference to neuronal regulation. Cell Tissue Res 220: 511–518Google Scholar
  12. Hökfelt T, Fuxe K, Johansson O, Jeffcoate S, White N (1975) Distribution of thyrotropin-releasing hormone (TRH) in the central nervous system as revealed with immunohistochemistry. Eur J Pharmacol 34: 389–392Google Scholar
  13. Ishikawa K, Kakegawa T, Suzuki M (1984) Role of hypothalamic paraventricular nucleus in the secretion of thyrotropin under adrenergic and cold-stimulated conditions in the rat. Endocrinology 114: 352–358Google Scholar
  14. Johansson O, Hökfelt T (1980) Thyrotropin releasing hormone, somatostatin, and enkephalin: distribution studies using immunohistochemical techniques. J Histochem Cytochem 28: 364–366Google Scholar
  15. Johansson O, Hökfelt T, Jeffcoate SL, White N, Sternberger LA (1980) Ultrastructural localization of TRH-like immunoreactivity. Exp Brain Res 38: 1–10Google Scholar
  16. Kawano H, Daikoku S, Saito S (1982) Immunohistochemical studies of intrahypothalamic somatostatin-containing neurons in rat. Brain Res 242: 227–232Google Scholar
  17. Kiss JZ, Williams TH (1983) ACTH-immunoreactive boutons form synaptic contacts in the hypothalamic arcuate nucleus of rat: evidence for local opiocortin connections. Brain Res 263: 142–146Google Scholar
  18. Krulich L, Giachetti A, Marchlewska-Koj A, Hefco E, Jameson HE (1977) On the role of the central noradrenergic and dopaminergic systems in the regulation of TSH secretion in the rat. Endocrinology 100: 496–505Google Scholar
  19. Lechan RM, Jackson IMD (1982) Immunohistochemical localization of thyrotropin-releasing hormone in the rat hypothalamus and pituitary. Endocrinology 111: 55–65Google Scholar
  20. Lechan RM, Nestler JL, Jacobson S (1982) The tubero-infundibular system of the rat as demonstrated by immunohistochemical localization of retrogradely transported wheat germ agglutinin (WGA) from the median eminence. Brain Res 245: 1–15Google Scholar
  21. Léránth C, Williams TH, Hamori J, Chretien M (1981) Light and electron microscopic immunocytochemical localization of adrenocorticotrophin-like activity in rat cerebellar and red nuclei. Neuroscience 6: 481–487Google Scholar
  22. Léránth C, Sakamoto H, MacLusky NJ, Shanabrough M, Naftolin F (1985) Intrinsic tyrosine hydroxylase (TH) immunoreactive axons synapse with TH immunopositive neurons in the rat arcuate nucleus. Brain Res 331: 371–375Google Scholar
  23. Martin JB, Reichlin S (1972) Plasma thyrotropin (TSH) response to hypothalamic electrical stimulation and to injection of synthetic thyrotropin releasing hormone (TRH). Endocrinology 90: 1079–1085Google Scholar
  24. Nishiyama T, Kawano H, Tsuruo Y, Maegawa M, Hisano S, Adachi T, Daikoku S, Suzuki M (1985) Hypothalamic thyrotropin-releasing hormone (TRH)-containing neurons involved in the hypothalamic-hypophysial-thyroid axis. Light microscopic immunohistochemistry. Brain Res 345: 205–218Google Scholar
  25. Palkovits M, Eskay RL, Brownstein MJ (1982) The course of thyrotropin-releasing hormone fibers to the median eminence in rats. Endocrinology 110: 1526–1528Google Scholar
  26. Renaud LP, Martin JB, Brazeau P (1975) Depressant action of TRH, LH-RH and somatostatin on activity of central neurons. Nature 255: 233–235Google Scholar
  27. Shioda S, Nakai Y (1983) Immunocytochemical localization of TRH and autoradiographic determination of3H-TRH-binding sites in the arcuate nucleus-median eminence of the rat. Cell Tissue Res 228: 475–487Google Scholar
  28. Theodosis DT (1985) Oxytocin-immunoreactive terminals synapse on oxytocin neurons in the supraoptic nucleus. Nature 313: 682–684Google Scholar
  29. Tsuruo Y, Hisano S, Daikoku S (1984) Morphological evidence for synaptic junctions between substance P-containing neurons in the arcuate nucleus of the rat. Neurosci Lett 46: 65–69Google Scholar
  30. Tuomisto J, Ranta T, Nännistö P, Saarinen A, Leppäluoto J (1975) Neurotransmitter control of thyrotropin secretion in the rat. Eur J Pharmacol 30: 221–229Google Scholar
  31. Winokur A, Davis R, Utiger RD (1977) Subcellular distribution of thyrotropin-releasing hormone (TRH) in rat brain and hypothalamus. Brain Res 120: 423–434Google Scholar

Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • S. Hisano
    • 1
  • H. Ishizuka
    • 2
  • T. Nishiyama
    • 1
  • Y. Tsuruo
    • 1
  • S. Katoh
    • 1
  • S. Daikoku
    • 1
  1. 1.Department of Anatomy, School of MedicineThe University of TokushimaTokushimaJapan
  2. 2.Department of Oral AnatomySchool of Dentistry, The University of TokushimaTokushimaJapan

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