Intrathecal FMRFamide (Phe-Met-Arg-Phe-NH₂) induces excessive grooming behavior in mice

The molluscan neuropeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide) was administered intrathecally (i.t.) to mice and their behavior was monitored for 30 min. FMRFamide induced a dramatic and dose-related (5-12 μg) increase in grooming-related activities compared to saline-treated controls. The grooming behavior produced by 8 μg FMRFamide was not blocked by simultaneous i.t. administration of 10 μg of the following antagonists: atropine, phentolamine, methysergide, naloxone or spantide; peripheral administration of naloxone (3.5 mg/kg, s.c.) also failed to antagonize FMRFamide grooming. These data constitute the first report that FMRFamide produces behavioral changes in mammals.