Association of cocaine- and amphetamine-regulated transcript-immunoreactive elements with thyrotropin-releasing hormone-synthesizing neurons in the hypothalamic paraventricular nucleus and its role in the regulation of the hypothalamic-pituitary-thyroid axis during fasting.
Because cocaine- and amphetamine-regulated transcript (CART) coexists with alpha-melanocyte stimulating hormone (alpha-MSH) in the arcuate nucleus neurons and we have recently demonstrated that alpha-MSH innervates TRH-synthesizing neurons in the hypothalamic paraventricular nucleus (PVN), we raised the possibility that CART may also be contained in fibers that innervate hypophysiotropic thyrotropin-releasing hormone (TRH) neurons and modulate TRH gene expression. Triple-labeling fluorescent in situ hybridization and immunofluorescence were performed to reveal the morphological relationships between pro-TRH mRNA-containing neurons and CART- and alpha-MSH-immunoreactive (IR) axons. CART-IR axons densely innervated the majority of pro-TRH mRNA-containing neurons in all parvocellular subdivisions of the PVN and established asymmetric synaptic specializations with pro-TRH neurons. However, whereas all alpha-MSH-IR axons in the PVN contained CART-IR, only a portion of CART-IR axons in contact with pro-TRH neurons were immunoreactive for alpha-MSH. In the medial and periventricular parvocellular subdivisions of the PVN, CART was co-contained in approximately 80% of pro-TRH neuronal perikarya, whereas colocalization with pro-TRH was found in <10% of the anterior parvocellular subdivision neurons. In addition, >80% of TRH/CART neurons in the periventricular and medial parvocellular subdivisions accumulated Fluoro-Gold after systemic administration, suggesting that CART may serve as a marker for hypophysiotropic TRH neurons. CART prevented fasting-induced suppression of pro-TRH in the PVN when administered intracerebroventricularly and increased the content of TRH in hypothalamic cell cultures. These studies establish an anatomical association between CART and pro-TRH-producing neurons in the PVN and demonstrate that CART has a stimulatory effect on hypophysiotropic TRH neurons by increasing pro-TRH gene expression and the biosynthesis of TRH.
Fekete
C
C
Tupper Research Institute and Department of Medicine, Division of Endocrinology, Diabetes, Metabolism and Molecular Medicine, New England Medical Center, Boston, Massachusetts 02111, USA.
Mihály
E
E
Luo
L G
LG
Kelly
J
J
Clausen
J T
JT
Mao
Q
Q
Rand
W M
WM
Moss
L G
LG
Kuhar
M
M
Emerson
C H
CH
Jackson
I M
IM
Lechan
R M
RM
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002452:Cell Count; D002478:Cells, Cultured; D003078:Colchicine / Q000008:administration & dosage; D005215:Fasting / Q000378:metabolism*; D005456:Fluorescent Dyes; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007276:Injections, Intraventricular; D008297:Male; D009419:Nerve Tissue Proteins / Q000008:administration & dosage / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010286:Paraventricular Hypothalamic Nucleus / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D011498:Protein Precursors / Q000096:biosynthesis* / Q000235:genetics; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D012333:RNA, Messenger / Q000378:metabolism; D011859:Radiography; D051381:Rats; D017207:Rats, Sprague-Dawley; D013266:Stilbamidines; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000096:biosynthesis* / Q000235:genetics; D013974:Thyroxine / Q000097:blood; D000521:alpha-MSH / Q000378:metabolism; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D009419:Nerve Tissue Proteins; D011498:Protein Precursors; D012333:RNA, Messenger; D013266:Stilbamidines; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D000521:alpha-MSH; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; C046418:pro-thyrotropin releasing hormone; D013974:Thyroxine; D003078:Colchicine; D011761:Pyrrolidonecarboxylic Acid