Departamento de Patologia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Av. Prof. Dr. Orlando Marques de Paiva, 87, Cidade Universitária, São Paulo SP, CEP 05588-000, Brasil.
Physiol Behav. 2010 Aug 4;101(1):40-4. doi: 10.1016/j.physbeh.2010.04.013. Epub 2010 Apr 21.
Previous studies have demonstrated that treatment of postpartum female rats with morphine inhibits maternal behavior and stimulates foraging. Exposure to drugs of abuse may result in a progressive enhancement of their reinforcing effects. Puerperal treatment with morphine leads to reverse tolerance to this drug. The present study investigated whether repeated morphine treatment during late pregnancy may influence the effects of different morphine dosages on behavioral selection in lactating rats. Females were simultaneously exposed to pups and insects, and the choice between taking care of the pups and hunting insects was observed. Female Wistar rats were treated with morphine (3.5 mg/kg/day, subcutaneous [s.c.]) or saline for 5 days beginning on pregnancy day 17. On day 5 of lactation, animals were acutely challenged with morphine (0.5, 1.0, or 1.5 mg/kg, s.c.; MM0.5, MM1.0, and MM1.5 groups, respectively) or saline (MS group) and tested for predatory hunting and maternal behavior. Control groups were pretreated with saline and challenged with morphine (SM0.5, SM1.0, and SM1.5 groups) or saline (SS group). Animals treated with morphine during late pregnancy and acutely challenged with 1.0 mg/kg morphine (MM1.0 group) exhibited significantly decreased maternal behavior and enhanced hunting. This effect was not evident with the 0.5 mg/kg dose. The 1.5 mg/kg morphine dose decreased maternal behavior and increased hunting in both the MM1.5 group and in animals challenged with morphine after previous saline treatment (SM1.5 group). These results provide evidence of plasticity of the opioidergic role in behavioral selection during lactation.
先前的研究表明，产后雌性大鼠接受吗啡治疗会抑制母性行为并刺激觅食。滥用药物会导致其强化作用逐渐增强。产后用吗啡治疗会导致对这种药物的反向耐受。本研究调查了在妊娠晚期反复给予吗啡是否会影响不同吗啡剂量对哺乳期大鼠行为选择的影响。雌性 Wistar 大鼠同时暴露于幼崽和昆虫中，并观察它们在照顾幼崽和捕猎昆虫之间的选择。雌性 Wistar 大鼠从妊娠第 17 天开始接受吗啡（3.5 mg/kg/天，皮下）或生理盐水治疗 5 天。在哺乳期第 5 天，动物接受吗啡（0.5、1.0 或 1.5 mg/kg，皮下；MM0.5、MM1.0 和 MM1.5 组）或生理盐水（MS 组）急性挑战，并测试捕食性捕猎和母性行为。对照组用生理盐水预处理，用吗啡（SM0.5、SM1.0 和 SM1.5 组）或生理盐水（SS 组）挑战。在妊娠晚期接受吗啡治疗并接受 1.0 mg/kg 吗啡急性挑战的动物（MM1.0 组）表现出明显减少的母性行为和增强的捕猎行为。0.5 mg/kg 剂量没有明显效果。1.5 mg/kg 吗啡剂量在 MM1.5 组和先前接受生理盐水治疗后接受吗啡挑战的动物（SM1.5 组）中均降低了母性行为并增加了捕猎行为。这些结果为哺乳期阿片类作用在行为选择中的可塑性提供了证据。
