GHRP-6 mimics ghrelin-induced stimulation of food intake and suppression of locomotor activity in goldfish
- GHRP-6 mimics ghrelin-induced stimulation of food intake and suppression of locomotor activity in goldfish
- Yahashi Satowa; 강기성; Hiroyuki Kaiya; Kouhei Matsuda
- GHRP-6; Ghrelin; Food intake; Locomotor activity; Capsaicin; Vagal afferent; Goldfish; GHS; GHS-R; GHS-R2a-1
- Issue Date
- VOL 34, NO 2, 324-328
- Ghrelin was first identified and characterized from rat stomach as an endogenous ligand for the growth
hormone secretagogue (GHS) receptor (GHS-R). Ghrelin also acts as an orexigenic factor and regulates
energy balance in rodents. In goldfish, native ghrelin consists of 11 molecular variants, the major form
being a 17-residue peptide with n-octanoic acid modification (n-octanoyl ghrelin17), and intraperitoneal
(IP) administration of n-octanoyl ghrelin17 induces central actions such as stimulation of food intake and
suppression of locomotor activity through capsaicin-sensitive afferents. Four types of GHS-Rs (1a-1, 1a-2,
2a-1 and 2a-2) have been identified in goldfish, and one GHS, GHRP-6, can activate only GHS-R2a-1 in
vitro. However, there is no information about the effect of GHRP-6 on food intake and locomotor activity
in goldfish in vivo. Therefore, in the present study, we examined whether IP-administered GHRP-6
would mimic the orexigenic action of n-octanoyl ghrelin17 and its suppression of locomotor activity. IP
administration of GHRP-6 at 1 pmol/g body weight (BW) stimulated food intake, and was equipotent to
the orexigenic action of n-octanoyl ghrelin17 at 10 pmol/g BW. IP-injected GHRP-6 at 1 pmol/g BW also
induced a significant decrease of locomotor activity, as was the case for IP-injected n-octanoyl ghrelin17
at 10 pmol/g BW. The action of GHRP-6 was blocked by IP-preinjected capsaicin at 160 nmol/g BW.
These results suggest that the central action of GHRP-6 might be mediated via the GHS-R2a-1-signaling
pathway, and subsequently through capsaicin-sensitive afferents in goldfish.
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