Ghrelin injected into the paraventricular nucleus of the hypothalamus of male rats induces feeding but not penile erection.
Melis. Maria Rosario MR; Mascia. Maria Stefania MS; Succu. Salvatora S; Torsello. Antonio A; Muller. Eugenio E EE; Deghenghi. Romano R; Argiolas. Antonio A
Key Findings
- Ghrelin injected into the PVN strongly increases feeding (up to 355% of normal) but does not induce penile erection.
- EP 80661, a hexarelin analogue, induces dose‑dependent penile erection but does not affect feeding when injected into the same brain region.
- Blocking neuropeptide Y Y5 receptors stops ghrelin‑driven feeding but does not affect EP 80661‑induced erection, indicating distinct receptor mechanisms.
Practical Outcomes
- For biohackers, this suggests that hexarelin‑type peptides may have pro‑erectile properties that are independent of appetite effects, but the results come from direct brain injections in rats, not from the typical peripheral dosing used by humans. It hints that hexarelin could be explored for sexual health benefits without causing weight gain, though more human‑focused research is needed before applying it in real‑world protocols.
Summary
In male rats, injecting ghrelin into a brain area called the paraventricular nucleus (PVN) makes the animals eat a lot but does not cause erections. A synthetic peptide similar to hexarelin (called EP 80661) does the opposite: it triggers erections without boosting food intake. The two effects use different versions of the same GH‑secretagogue receptor, meaning the pathways for appetite and sexual function are separate.
Abstract
The effect of ghrelin, a recently characterized endogenous receptor agonist for growth hormone (GH) secretagogue receptors, on feeding and penile erection was compared with that of EP 80661, a peptide analogue of the GH secretagogue hexarelin, previously identified for its pro-erectile activity when injected into the paraventricular nucleus of the hypothalamus of male rats. Ghrelin (0.01-1 microg), but not EP 80661 (0.02-1 microg), was found to be particularly effective in enhancing feeding. The minimal effective dose of ghrelin was 0.1 microg, which increased food intake by 88%, while the maximal response (355% above control values) was found with 1 microg of the peptide. The enhancing effect of ghrelin on feeding was prevented by the prior administration of the neuropeptide Y Y5 receptor antagonist (DTyr(2), DThr(32)) neuropeptide Y (NPY, 10 microg), but not by the GH-RH receptor antagonist MZ-4-71 (10 microg), or by EP 91073, a hexarelin analogue that antagonizes the pro-erectile effect of EP 80661 (10 microg), given into the lateral ventricles. In contrast, ghrelin failed to induce penile erection at all doses tested, while EP 80661 induced penile erection in a dose-dependent manner. The pro-erectile effect of EP 80661 was prevented by EP 91073 (10 microg), but not by (DTyr(2), DThr(32)) NPY (10 microg) or by the GH-RH receptor antagonist MZ 4-71 (10 microg), given into the lateral ventricles. The present results provide further support to the hypothesis that the GH secretagogue receptors mediating feeding are different from those mediating penile erection and activated by pro-erectile EP peptides.
Study Information
pubmed
2002
2002-09-06T00:00:00.000Z
10.1016/s0304-3940(02)00673-0