Study summary · research use only
Attenuation of Visceral and Somatic Nociception by Ghrelin Mimetics
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
In this rat study, researchers examined whether ghrelin receptor-mediated mechanisms reduce visceral and somatic pain absent active inflammation, testing a peripherally restricted ghrelin mimetic (ipamorelin) and a globally active ghrelin receptor agonist (HM01). Visceral hypersensitivity was induced by dilute acetic acid infusion into the rat colon without colonic inflammation, and somatic mechanical allodynia was assessed using von Frey filaments; the ghrelin receptor antagonist H0900 was also administered. Colonic sensitivity was measured as a visceromotor response to graded colorectal distension pressures. Versus vehicle controls, HM01 and ipamorelin were associated with attenuated colonic hypersensitivity and somatic allodynia, and these anti-nociceptive effects were blocked by co-administered H0900, indicating ghrelin receptor-mediated mechanisms in visceral and somatic hypersensitivity without active colonic inflammation.
Abstract
The anti-nociceptive properties of ghrelin have been demonstrated in alleviating inflammatory and neuropathic pain. Whether a ghrelin receptor-mediated mechanism attenuates visceral and somatic pain in the absence of active inflammation remains to be explored. Here, we investigate the efficacy of peripherally restricted (ipamorelin) and a globally active (HM01) selective ghrelin receptor agonist in an experimental model of non-inflammatory visceral hypersensitivity and somatic mechanical allodynia. Visceral hypersensitivity was induced by dilute acetic acid (0.6%) infusion in the colon of rats in the absence of colonic epithelial inflammation. Ghrelin mimetics HM01 and ipamorelin were administered orally or intravenously, respectively. The ghrelin receptor antagonist H0900 was administered orally. Colonic sensitivity was assessed via a visceromotor behavioral response (VMR) quantified as the number of abdominal contractions in response to graded isobaric pressures (0-60 mmHg) of colorectal distension (CRD). Somatic mechanical allodynia was quantified by the number of ipsilateral paw withdrawals in response to a calibrated von Frey filament. Compared to vehicle controls, ghrelin mimetics HM01 and ipamorelin significantly attenuated colonic hypersensitivity and somatic allodynia. The anti-nociceptive effects of the ghrelin mimetics were blocked after administration of the ghrelin receptor antagonist H0900. We have shown that ghrelin receptor-mediated mechanisms are involved in visceral and somatic hypersensitivity in the absence of active colonic inflammation. Furthermore, visceral and somatic hypersensitivity could be attenuated by a peripherally restricted ghrelin mimetic. These results highlight a potential novel approach for treating acute visceral and somatic pain by ghrelin mimetics.
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