Lack of interaction between peripheral injection of CCK and obestatin in the regulation of gastric satiety signaling in rodents

Obestatin is a new peptide for which anorexigenic effects were recently reported in mice. We investigate whether peripheral injection of obestatin or co-injection with cholecystokinin (CCK) can modulate food intake, gastric motor function (intragastric pressure and emptying) and gastric vagal afferent activity in rodents. Obestatin (30, 100 and 300 μg/kg, i.p.) did not influence cumulative food intake for the 2 h post-injection in rats or mice nor gastric emptying in rats. In rats, obestatin (300 μg/kg) did not modify CCK (1 μg/kg, i.p.)-induced significant decrease in food intake (36.6%) and gastric emptying (31.0%). Furthermore, while rats injected with CCK (0.3 μg/kg, i.v.) displayed gastric relaxation, no change in gastric intraluminal pressure was elicited by obestatin (300 μg/kg, i.v.) pre- or post-CCK administration. In in vitro rat gastric vagal afferent preparations, 20 units that had non-significant changes in basal activity after obestatin at 30 μg responded to CCK at 10 ng by a 182% increase. These data show that obestatin neither influences cumulative food intake, gastric motility or vagal afferent activity nor CCK-induced satiety signaling