Open-field behavior of rats following intracerebroventricular administration of neuromedin B, neuromedin C, and related amphibian peptides.

Neuromedin B (NMB) and neuromedin C (NMC) have amino acid sequences similar to those of various amphibian skin peptides and thus may elicit behavioral effects similar to those of bombesin. The present study was performed to determine the central effects of neuromedins (including pyro-NMB and pyro-NMC) in comparison with those of amphibian peptides using an open-field test situation. At 1 min after intracerebroventricular administration of the peptides, there was a marked decrease in the duration of locomotion, the distance moved, and rearing behavior, but a marked increase of excessive grooming and violent scratching. Pronounced behavioral changes were still observed 30 min after injection of the peptides, except for NMB. Thus, NMB seemed to be rapidly degraded by endogenous peptidases in the brain, suggesting that it might be the essential form of this neuropeptide family in the mammalian brain.