Kinsley C H, Bridges R S
Laboratory of Human Reproduction, Harvard Medical School.
Dev Psychobiol. 1990 May;23(4):331-47. doi: 10.1002/dev.420230405.
Administration of morphine sulfate (MS) to pregnancy-terminated and postpartum lactating female rats disrupts both maternal behavior and postpartum aggression. Since the display of these behaviors may be heavily dependent on olfactory cues provided by the stimulus animals (rat pups and adult male rats, respectively), we examined whether MS was affecting the perception of the olfactory stimuli, and whether olfactory perception was modified by reproductive condition. In Experiment 1, lactating rats had their pups removed and were injected with MS (5.0 mg/kg, sc.) or saline. 60 min later they were placed into a two-choice apparatus, one side of which contained bedding soiled by neonates and the other clean bedding. Time spent on each side was recorded for a total of 5 min (300 s; chance = 150 s). Saline-treated mothers spent significantly more time on the pup-odor side, whereas MS-treated females spent significantly less. In Experiment 2, lactating females were treated with MS or saline and exposed to male odors (soiled bedding). MS significantly increased time spent on the side with male odors; when treated with saline, time spent was significantly reduced. Thus, in lactating rats. MS creates an aversion for pup odors while reducing the female's normal aversion toward male odors. In Experiment 3, ovariectomized (ovx) virgin females expressed neither an aversion nor a preference for the odor of pups following saline administration. After MS treatment, however, the virgins showed a distinct preference for pup odors. When exposed to male odors in Experiment 4 ovx virgins showed a marked preference for male odors after MS treatment, and neither a preference nor an aversion after saline. Experiment 5 examined pup odor preferences in intact virgins, early (Day 7), middle (Day 14), late-pregnant (Day 21), and prepartum (Day 22) rats. The pup odor preferences of virgin, Day 7, Day 14, and Day 21 pregnant rats were not different and generally were at chance levels. Day 22 pregnant females exhibited a marked preference for pup odors compared to chance levels, as well as compared to the other four groups. These findings suggest that opiates and endogenous opioids may regulate olfactory preferences and that alterations in this system may underlie normal behavioral changes toward conspecifics prepartum as well as during lactation.
给妊娠终止后的雌性大鼠和产后哺乳期雌性大鼠注射硫酸吗啡（MS）会扰乱母性行为和产后攻击性。由于这些行为的表现可能严重依赖于刺激动物（分别是幼鼠和成年雄鼠）提供的嗅觉线索，我们研究了MS是否影响对嗅觉刺激的感知，以及嗅觉感知是否会因生殖状态而改变。在实验1中，将哺乳期大鼠的幼崽移除，并给它们注射MS（5.0毫克/千克，皮下注射）或生理盐水。60分钟后，将它们放入一个二选一装置中，装置的一侧放置有新生幼崽弄脏的垫料，另一侧放置干净的垫料。记录它们在每一侧停留的时间，总共记录5分钟（300秒；随机概率为150秒）。注射生理盐水的母鼠在有幼崽气味的一侧停留的时间明显更长，而注射MS的母鼠停留的时间明显更短。在实验2中，给哺乳期雌性大鼠注射MS或生理盐水，并让它们接触雄性气味（弄脏的垫料）。MS显著增加了在有雄性气味一侧停留的时间；注射生理盐水时，停留时间显著减少。因此，在哺乳期大鼠中，MS会产生对幼崽气味的厌恶，同时减少雌性对雄性气味的正常厌恶。在实验3中，切除卵巢的处女雌鼠在注射生理盐水后对幼崽气味既无厌恶也无偏好。然而，在接受MS治疗后，这些处女雌鼠对幼崽气味表现出明显的偏好。在实验4中，当切除卵巢的处女雌鼠接触雄性气味时，接受MS治疗后对雄性气味表现出明显的偏好，注射生理盐水后则既无偏好也无厌恶。实验5研究了未交配的处女鼠、妊娠早期（第7天）、中期（第14天）、晚期（第21天）和产前（第22天）大鼠对幼崽气味的偏好。未交配的处女鼠、妊娠第7天、第14天和第21天的大鼠对幼崽气味的偏好没有差异，总体上处于随机水平。与随机水平相比，以及与其他四组相比，妊娠第22天的雌性大鼠对幼崽气味表现出明显的偏好。这些发现表明，阿片类药物和内源性阿片肽可能调节嗅觉偏好，并且该系统的改变可能是产前以及哺乳期对同种个体正常行为变化的基础。
