GH-deficient dw/dw rats and lit/lit mice show increased Fos expression in the hypothalamic arcuate nucleus following systemic injection of GH-releasing peptide-6

in Journal of Endocrinology
Authors:
S L Dickson
Search for other papers by S L Dickson in
Current site
Google Scholar
PubMed
Close
,
O Doutrelant-Viltart
Search for other papers by O Doutrelant-Viltart in
Current site
Google Scholar
PubMed
Close
, and
G Leng
Search for other papers by G Leng in
Current site
Google Scholar
PubMed
Close
Restricted access
Rent on DeepDyve

Sign up for journal news

Abstract

In the rat, the synthetic GH secretagogue GH-releasing peptide (GHRP-6) acts centrally to activate a subpopulation of arcuate neurones as reflected by increased electrical activation and by the detection of Fos protein in cell nuclei. Since GHRP-6 also induces GH secretion via a direct action on the pituitary, we set out to determine whether the central actions of GHRP-6 are mediated by GH itself. First, we demonstrated that peripherally administered GHRP-6 induces Fos expression in the arcuate nucleus of GH-deficient animals (dw/dw rats and lit/lit mice). Secondly, in dw/dw rats, neither intracerebro-ventricular injection of 15 μg recombinant bovine GH nor 1 μg recombinant human IGF-I resulted in an increase in the number of cells expressing Fos protein in the arcuate nucleus (or in any other hypothalamic structure studied). These results support our hypothesis that GHRP-6 has a central site and mechanism of action and provide evidence to suggest that the activation of arcuate neurones by GHRP-6 is not mediated by a central action of GH or IGF-I. Furthermore, since the lit/lit mouse pituitary does not release GH following GHRP-6 administration, our finding that the central actions of GHRP-6 remain intact in these animals suggests the possible existence of two subpopulations of putative GHRP-6 receptors.

Journal of Endocrinology (1995) 146, 519–526

 

  • Collapse
  • Expand