Dissemin is shutting down on January 1st, 2025

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Karger Publishers, Pharmacology, 1(83), p. 38-44, 2008

DOI: 10.1159/000178811

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Lack of Protection with a Novel, Selective Melanocortin Receptor Subtype-4 Agonist RY767 in a Rat Transient Middle Cerebral Artery Occlusion Stroke Model

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

Previous studies utilizing α-melanocyte-stimulating hormone (α-MSH) or the synthetic analog [Nle<sup>4</sup>, <i>D</i>-Phe<sup>7</sup>] α-MSH have reported beneficial effects in animal models of ischemic stroke, with the latter studies suggesting melanocortin receptor subtype-4 (MC4R) activation as a protective mechanism. The present study directly addresses the hypothesis that MC4R activation may ameliorate ischemic brain injury by assessing the efficacy of a novel small molecule MC4R agonist RY767, administered in a pharmacokinetically guided and pharmacologically validated dosing regimen, in a rat stroke model of transient middle cerebral artery occlusion (tMCAO). Male Wistar rats were subjected to 90-min tMCAO followed by 72 h of reperfusion. Treatments were i.p. pretreatment with MK-801 (15 min prior to occlusion, positive control), or combined i.v. and p.o. daily administrations of vehicle, dextrose (negative control) or RY767 in blinded fashion initiated 2 h after occlusion. Infarct volume in MK-801-treated rats (158.7 ± 22.3 mm<sup>3</sup>) was reduced significantly compared to vehicle infarct volume (243.4 ± 12.5 mm<sup>3</sup>), whereas infarct volumes in dextrose- (224.3 ± 16.5 mm<sup>3</sup>) and RY767- (262.1 ± 19.2 mm<sup>3</sup>) treated rats did not differ from vehicle infarct volume. These results indicate that selective MC4R activation provides no significant neuroprotection, as reflected by infarct volume, in a rat stroke model utilizing a 90-min ischemic insult.