Glutamatergic innervation of corticotropin-releasing hormone- and thyrotropin-releasing hormone-synthesizing neurons in the hypothalamic paraventricular nucleus of the rat.
Glutamate plays a role in the central regulation of the hypothalamic-pituitary-adrenal (HPA) and thyroid (HPT) axes. Until the recent discovery of vesicular glutamate transporters (VGLUT1-3), there was no specific tool for the examination of the putative morphological relationship between the glutamatergic and the hypophysiotropic systems. Using antisera against VGLUT2, corticotropin-releasing hormone (CRH), and prothyrotropin-releasing hormone (proTRH) (178-199), we performed double-labeling immunocytochemistry at light and electron microscopic levels in order to study the glutamatergic innervation of the CRH- and TRH-synthesizing neurons in the hypothalamic paraventricular nucleus (PVN). Fine VGLUT2-immunoreactive (IR) axons very densely innervated the parvocellular subdivisions of the PVN. VGLUT2-IR axons established juxtapositions with all parvocellular CRH- and TRH-synthesizing neurons. The innervation was similarly intense in all parvocellular subdivisions of the PVN. At ultrastructural level, VGLUT2-IR terminals frequently established synapses with perikarya and dendrites of the CRH- and proTRH-IR neurons. These findings demonstrate that glutamatergic neurons directly innervate hypophysiotropic CRH and TRH neurons in the PVN and, therefore, support the hypothesis that the glutamate-induced activation of the HPA and HPT axes may be accomplished by a direct action of glutamate on hypophysiotropic CRH and TRH systems.
Wittmann
Gábor
G
Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest 1083, Hungary.
Lechan
Ronald M
RM
Liposits
Zsolt
Z
Fekete
Csaba
C
D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D018698:Glutamic Acid / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009434:Neural Pathways / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D010913:Pituitary-Adrenal System / Q000502:physiology; D011498:Protein Precursors / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D014018:Tissue Distribution; D050599:Vesicular Glutamate Transport Protein 2
D026901:Membrane Transport Proteins; D011498:Protein Precursors; C493475:Slc17a6 protein, rat; D050599:Vesicular Glutamate Transport Protein 2; D018698:Glutamic Acid; D013973:Thyrotropin-Releasing Hormone; D003346:Corticotropin-Releasing Hormone; C046418:pro-thyrotropin releasing hormone; D011761:Pyrrolidonecarboxylic Acid