GHRP-2 (short for Growth Hormone Releasing Peptide-2) is an agonist of the ghrelin receptor. Ghrelin has wide-ranging effects that include growth hormone release and protection of cardiac (heart) muscle cells. Scientific studies based on animal test subjects suggests that both ghrelin and its receptor agonists, like GHRP-6, may also play a significant role in memory formation.
Fear Memory Encoding
One of the primary roles of memory in animals is to store associations regarding safe and dangerous encounters. Fear is one of the most potent memory stimulants known. The fear memory-encoding mechanism has been isolated to a region of the brain called the lateral amygdala and years of research have demonstrated changes in this brain region occur in response to fear conditions. It is also well-accepted that learning not to fear a previously feared condition is exceptionally difficult.
Animal studies have found that food deprivation can increase the rate at which a fear response is lost (fear extinction) . In other words, not eating can actually increase the rate of learning how to not be afraid. It was thought that this effect may be related to the elevated levels of ghrelin that occur with food deprivation, a hypothesis that was confirmed when blocking of ghrelin receptors was found to impair fear extinction in rats .
Studies with GHRP-6 and Memory
Very recent work has found that GHRP-6 administration immediately after learning, can improve retention in rats. Additionally, rats that have no ghrelin receptor 1a take much longer to learn new tasks, even with GHRP-6 injection, suggesting that ghrelin and its analogues are highly active in memory formation . Older research using GHRP-6 has also demonstrated a benefit in spatial learning (ability to navigate a maze) among rats who had GHRP-6 injected directly into their amygdalas .
Teasing Out Nuance
It has been known for some time that growth hormone (GH) plays a role in memory, mental alertness, and motivation , . This is part of the reason that exercise has been linked to improvements in memory and learning because exercise itself has been shown to help increase natural growth hormone levels. At least part of the benefit of GHRP-6 and ghrelin analogues stems from their GH releasing properties, but this doesn’t account for the entirety of their benefits. There is some speculation that they may benefit memory by directly modulating the brain’s insulin-like growth factor (IGF) system. IGF levels and IGF-1 expression are known to impact neuron health and both are impacted by GH levels. The brain IGF system may be the common link that ties together the effects on memory of both GH and molecules like GHRP-6.
 C.-C. Huang, D. Chou, C.-M. Yeh, and K.-S. Hsu, “Acute food deprivation enhances fear extinction but inhibits long-term depression in the lateral amygdala via ghrelin signaling,” Neuropharmacology, vol. 101, pp. 36-45, Sep. 2015.
 S. Beheshti and S. Shahrokhi, “Blocking the ghrelin receptor type 1a in the rat brain impairs memory encoding,” Neuropeptides, vol. 52, pp. 97-102, Aug. 2015.
 K. Tóth, K. László, and L. Lénárd, “Role of intraamygdaloid acylated-ghrelin in spatial learning,” Brain Res. Bull., vol. 81, no. 1, pp. 33-37, Jan. 2010. For more information, go to https://www.theguardian.com/science/2016/nov/23/dogs-have-episodic-memories-just-like-humans-suggests-study
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 E. H. Quik, E. B. Conemans, G. D. Valk, J. L. Kenemans, H. P. F. Koppeschaar, and P. S. van Dam, “Cognitive performance in older males is associated with growth hormone secretion,” Neurobiol. Aging, vol. 33, no. 3, pp. 582-587, Mar. 2012.…Read More