Central opioid-like influence of a tetrapeptide from hamster embryo (kentsin) on gastrointestinal motility in dogs

The effects of intracerebroventricular (i.c.v.) vs. intravenous (i.v.) administration of kentsin (H-Thr-Pro-Arg-Lys-OH) on gastrointestinal motility were investigated in fasted dogs. Administered i.c.v. at doses of 20 and 100 ng/kg, this peptide inhibited by 51.2 and 76.1% the antral motility index and disrupted the jejunal migrating motor complex for 2 and 4 h respectively. Similar effects were only obtained after a 25 fold higher dose administered i.v. and these effects were abolished after a previous i.c.v. administration of naloxone (50 micrograms/kg) suggesting that they are mediated through opiate receptors.