Ghrelin relaxes the iris sphincter muscle through a GHSR-1a independent pathway.

• Type: Summary of Presentation in an International Conference
• Date: 2004

Authors

Rocha-Sousa A (Author) FMUP; Saraiva I (Author) Other; Gonzaga S (Author) Other; Correia-Pinto J (Author) FMUP; Falcão-Reis F (Author) FMUP; Leite-Moreira AF (Author) FMUP

Conference proceedings International

Title: Ophthalmic Research

Initial page: 156

European Association for Vision and Eye research (EVER).

Vilamoura, Portugal, 24 27 de Setembro de 2004

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

CORDIS: Health sciences > Medical sciences > Medicine > Ophthalmology

Other information

Resumo (PT): To characterize production and contractile effects of Ghrelin on iris sphincter muscle and the role of GHSR-1a in its mediation. Methods Cumulative doses of Des-octanoil 1-5 Ghrelin (Des-Ghr, 10e-9 to 6*10e-5M; n=10) or 1-5-Ghrelin (Ghr, 10e-9 to 6*10e-5M; n=54) to generate concentration-response curves were tested on precontracted (Carbacol; 10e-4M) rabbit iris sphincter muscles. Ghr was added in the absence (n=14) or presence of i) L-nitro-arginine (L-NA, 10e-4M; n=14); ii) indomethacin (10e-5M; n=14); iii) D-Lys-GHRP6, a selective GHSR-1a inhibitor (10e-4M; n=12). Results are expressed as % changes from control. Ghrelin production was assessed by “in situ” hybridization for detection of Ghrelin mRNA in Wistar rat eyes (n=7). Results Ghr and Des-Ghr promoted a concentration-dependent relaxation of the muscle maximal at 10e-5M, which relaxation of 34.1±12.1 % and 37.1±2.6 %. This was recorded 1.5-3 minutes after its addition to the bath and disappeared 10 minutes later. Although not statistically significant, there was a trend for L-NA to exacerbate and for indomethacin to attenuate Ghr’s relaxing effect (muscular tension decreased 58.0±10.5% and 20.3±12.1%, respectively). D-Lys3-GHRP6 significantly increased the relaxing effect of Ghr (118.1±21.1%). Ghrelin mRNA was identified in the posterior epithelium of the iris. Conclusions Ghrelin therefore is a novel, locally produced, relaxing agent of iris sphincter muscle. This effect has rapid onset, is transient and seems, to some extent, to be modulated by NO and prostaglandins. Its potentiation when GHSR-1a is inhibited and the similar effect of des-octanoil-ghrelin suggest a mediation through another type of GHS receptor.

Language: English

Type (Professor's evaluation): Scientific

Notes: European Association for Vision and Eye research (EVER), published in journal, Ophthalmic Research. 2004; 36(Suppl.1):156.