Neurotensin and bombesin: differential effects on body temperature of mice after intracisternal administration

Abstract

Intracisternal administration of neurotensin or bombesin produces a significant hypothermic response in rodents in an ambient temperature of 23°C or below; bombesin has been reported to produce a significant hyperthermic response in rats at 36°C, but no change in colonic temperature at ambient temperatures between 31 and 33°C. In this study we compared the effects of the two neuropeptides on colonic temperature of mice exposed to different ambient temperatures to determine whether neurotensin also produces a poikilothermic state. From a series of experiments conducted at ambient temperatures of 4, 23, 26, 30, 34 and 38°C, in which mice received an intracisternal injection of an equimolar dose (0.6 nmol) of neurotensin or bombesin (or vehicle), we noted that the two neuropeptides produce different effects on colonic temperature. At ambient temperatures of 26°C and below, both neurotensin and bombesin produce a significant hypothermic response; however, at higher temperatures bombesin has no effect (30°C) or produces hyperthermia (34°C). In contrast, neurotensin produces hypothermia at 30°C and no significant effect at 34 and 38°C. In addition, a wide range of doses of neurotensin failed to produce the poikilothermic effects characteristic of centrally administered bombesin.