GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
Systemic administration of ghrelin induces Fos and Egr-1 proteins in the hypothalamic arcuate nucleus of fasted and fed rats.
Hewson. A K AK; Dickson. S L SL
Key Findings
- Systemic (i.e., injected) ghrelin and GHRP‑6 both increase Fos and Egr‑1 protein expression in the hypothalamic arcuate nucleus, indicating direct central nervous system activation.
- The increase in these immediate‑early genes is significantly greater in fasted rats compared to fed rats.
- GHRP‑6 mimics the natural hormone ghrelin’s central effects, confirming it acts as a functional growth‑hormone secretagogue in the brain.
Practical Outcomes
- For biohackers, this suggests that taking GHRP‑6 while fasted may amplify its appetite‑stimulating and growth‑hormone‑releasing effects. Timing doses in a fasted window could enhance the peptide’s central actions, potentially improving metabolic and body‑composition outcomes. However, human data are needed to confirm the magnitude of this effect.
Summary
The study shows that giving ghrelin or the synthetic peptide GHRP‑6 to rats triggers activity in brain cells that control hunger and growth hormone, and this effect is much stronger when the animals are fasted. In simple terms, GHRP‑6 works not just in the body but also directly in the brain, and it does its best job when you take it on an empty stomach.
Abstract
Ghrelin, a recently identified endogenous ligand for the growth hormone secretagogue (GHS) receptor, induces growth hormone (GH) secretion following systemic administration. We sought to determine whether systemic administration of ghrelin activates cells in the hypothalamic arcuate nucleus by examining the distribution of cells expressing Fos and Egr-1 proteins. In normally fed rats, both ghrelin and GHRP-6 (a synthetic GHS) significantly increased the number of cells expressing Fos and Egr-1 in the arcuate nucleus. The effects of ghrelin and GHRP-6 to induce Fos or Egr-1 protein expression was significantly greater in fasted than in fed rats. Thus, we show that (i) ghrelin is a centrally active peptide; (ii) it acts in a similar manner to synthetic GHS; and (iii) its central actions are increased in fasting, presumably reflecting physiological changes that accompany altered food intake and/or nutritional state.
Study Information
pubmed
2000
2000-11-01T00:00:00.000Z
10.1046/j.1365-2826.2000.00584.x
368
12