The effects of pancreatic polypeptide on locomotor activity and food intake in mice.

Pancreatic polypeptide (PP) has been shown to inhibit food intake in both rodents and humans. Acute peripheral administration of PP increases oxygen consumption in obese mice. To further investigate the function of PP in the modulation of energy balance, we examined its effects on spontaneous locomotor activity and food intake in mice by using a 24-chamber Comprehensive Laboratory Animal Monitoring System. Effects of intraperitoneal (i.p.) administration of PP on spontaneous locomotor activity were measured using the optical beam technique. Administration of PP dose dependently inhibited cumulative food intake. The inhibition remained significant for up to 6, 17 and 36 h at doses of 30, 100 and 300 nmol kg(-1) PP, respectively. At 10 nmol kg(-1), PP increased locomotor activity (cumulative beam breaks) significantly for 4 h following administration without affecting food intake and at 30 nmol kg(-1), PP increased locomotor activity by 79% compared with the controls for 5 h post injection. However, at 100 and 300 nmol kg(-1), PP had no significant effect on locomotor activity. This study shows for the first time that PP increases spontaneous locomotor activity in mice.