Systemic administration of growth hormone-releasing peptide activates hypothalamic arcuate neurons.
The synthetic hexapeptide growth hormone-releasing peptide selectively releases growth hormone in many species including man. Growth hormone-releasing peptide directly stimulates growth hormone release by an action at the level of the pituitary, at a different receptor site to that for the endogenous 44-amino acid peptide, growth hormone-releasing hormone, and when administered with growth hormone-releasing hormone has a synergistic effect. In addition to this pituitary action, we have suggested that the potent in vivo growth hormone-releasing activity of growth hormone-releasing peptide reflects a hypothalamic action and growth hormone-releasing peptide binding sites have been reported to be present in the hypothalamus. We have now found more direct evidence for a hypothalamic action of growth hormone-releasing peptide in two ways. First, we have found that a sub-population of hypothalamic neurons show strongly increased fos expression in response to systemic growth hormone-releasing peptide administration. Fos is the protein product of the immediate early gene, c-fos, which is induced in many neuronal systems following their activation. Second, extracellular recordings from putative growth hormone-releasing hormone neurons in the arcuate nucleus showed that growth hormone-releasing peptide also stimulates the firing of neurons in this area.
Department of Neurobiology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, U.K.
S L
SL
Dickson
G
G
Leng
I C
IC
Robinson
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004594:Electrophysiology; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos / Q000187:drug effects; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats
D016760:Proto-Oncogene Proteins c-fos; D013007:Growth Hormone-Releasing Hormone