Behavioral responses elicited by intraperitoneal neurotensin in guinea pigs

The potential behavioral responses to single intraperitoneal (IP) injection of neurotensin (NT) were examined in conscious, freely moving guinea pigs. Most animals injected with NT solvent (i.e., controls) or NT solution with low NT concentration (i.e., 5.4 nM) exhibited little or no particular behavioral reaction. On the other hand, 50 to 75% of the animals given IP injection of NT with 54, 540, or 5400 nM of NT exhibited motor responses characterized by a transient episode of clonic body jerks. Vocalization responses were observed in less than 25% of the animals given IP NT. Animal pretreatment with morphine reduced the incidence of motor and vocalization responses. The results were interpreted as an indication that IP injection of moderately concentrated NT solution (i.e., greater than or equal to 54 nM) is probably a weak noxious stimulus in conscious guinea pigs.