Xenin—a novel suppressor of food intake in rats

Peptides related to the amphibian octapeptide xenopsin are present in various locations in mammalians, such as the gastrointestinal mucosa or brain tissue. In the gastrointestinal tract, xenopsin-related peptides induce partially neurogenic contractions of the colon in humans. In brain, however, their function is not known. Structural similarities of xenopsin-related peptides with neurotensin, a known modulator of ingestive behavior, suggest a possible role in feeding regulation. Therefore, we examined the effect of xenin, a recently identified xenopsin-related pentacosa peptide, on feeding behavior of fasted rats. Male Wistar rats ( n=12) were intracerebroventricularly (i.c.v.) injected with either saline (10 μl) or xenin at 0.5, 1.5, 5 or 15 μg dissolved in an identical volume of 10 μl, respectively. In further experiments, xenin 15 μg/0.5 μl or 0.5 μl saline were injected into the lateral hypothalamus (LH). After injections, food intake (g), percentage of time spent with feeding (%) and prandial water intake (ml) were subsequently recorded for 2 h. After i.c.v. injection of 15 μg of xenin 1-h food intake was significantly reduced by 42% and 2-h food intake was diminished by 25%, respectively, compared to saline injection ( p