Thyrotropin-releasing hormone-containing innervation of the histaminergic neurons in the tuberomammillary nucleus of rats
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1
Hungarian Academy of Sciences, Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungary
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2
Tufts-New England Medical Center , Tupper Research Institute and Department of Medicine, United States
Central administration of thyrotropin-releasing hormone (TRH) inhibits food intake, however, the neuronal pathways involved in the regulation of this effect are unknown. Similarly to TRH histamine also exerts inhibitory effect on the food intake. As blockade of histamine biosynthesis or administration of histamine 1 receptor (H1R) antagonists has been shown to decrease the anorexigen effect of TRH, the histaminergic neurons of the tuberomammillary nucleus (TMN) may be involved in the mediation of the anorexigenic effects of TRH neurons. In order to reveal the anatomical basis of this functional relationship between TRH and histamine, double-labeling immunohistochemistry was performed. Histamine-immunoreactive (IR) neurons were detected in the five subnuclei (E1-5) of the TMN. TRH-IR axons were observed in all subnuclei of the TMN, however, the TRH innervation of the E3 and E4 subnuclei was found to be more intense than the innervation of the other subnuclei. TRH-IR varicosities apposed to histaminergic neurons in all subnuclei of the TMN. The number of histamine-IR neurons juxtaposed by TRH-IR varicosities were the largest in the E3 and E4 subnuclei (63.6% and 63.4%). In these subnuclei, an average of 2.0 ± 1.3 (E3) and 1.5 ± 0.6 (E4) varicosities were observed on the surface of the connected histamine-IR neurons. In the E2 and E5 subnuclei about 50 % of histamine-IR neurons were juxtaposed by TRH-IR varicosities (49.0% and 50,0%; 1,5 ± 0.7 and 1,3 ± 0.5 varicosities/cell). The number of histamine-IR neurons juxtaposed by TRH-IR varicosities were the lowest in the E1 subnucleus (37.9%; 1,8 ± 1.2 varicosities/cell).
Our data demonstrate that TRH neurons establish direct connections with the histamine-IR cells of the TMN. Further studies determining the localization of TRH neurons involved in the innervations of histaminergic cell groups may help to elucidate which TRH cell populations are involved in the regulation of food intake.
Conference:
IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010.
Presentation Type:
Poster Presentation
Topic:
Homeostatic and neuroendocrine systems
Citation:
Sárvári
A,
Füzesi
T,
Liposits
Z,
Lechan
RM and
Fekete
C
(2010). Thyrotropin-releasing hormone-containing innervation of the histaminergic neurons in the tuberomammillary nucleus of rats.
Front. Neurosci.
Conference Abstract:
IBRO International Workshop 2010.
doi: 10.3389/conf.fnins.2010.10.00124
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Received:
28 Apr 2010;
Published Online:
28 Apr 2010.
*
Correspondence:
Anna Sárvári, Hungarian Academy of Sciences, Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Budapest, Hungary, samira@freestart.hu