Abrahao Karina Possa, Goeldner Francine Oliveira, Souza-Formigoni Maria Lucia Oliveira
Departamento de Psicobiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, SP, Brazil.
PLoS One. 2014 Jun 11;9(2):e98296. doi: 10.1371/journal.pone.0098296. eCollection 2014.
In mice there are clear individual differences in the development of behavioral sensitization to ethanol, a progressive potentiation of its psychomotor stimulant effect. Variability in the behavioral responses to ethanol has been associated with alcohol preference. Here we investigated if the functional hyperresponsiveness of D1 receptors observed in ethanol sensitized mice leads to an increased activation of DARPP-32, a central regulatory protein in medium spiny neurons, in the nucleus accumbens - a brain region known to play a role in drug reinforcement. Swiss Webster mice received ethanol (2.2 g/kg/day) or saline i.p. administrations for 21 days and were weekly evaluated regarding their locomotor activity. From those treated with ethanol, the 33% with the highest levels of locomotor activity were classified as "sensitized" and the 33% with the lowest levels as "non-sensitized". The latter presented similar locomotor levels to those of saline-treated mice. Different subgroups of mice received intra-accumbens administrations of saline and, 48 h later, SKF-38393, D1 receptor agonist 0.1 or 1 µg/side. Indeed, sensitized mice presented functional hyperresponsiveness of D1 receptors in the accumbens. Two weeks following the ethanol treatment, other subgroups received systemic saline or SKF 10 mg/kg, 20 min before the euthanasia. The nucleus accumbens were dissected for the Western Blot analyses of total DARPP-32 and phospho-Thr34-DARPP-32 expression. D1 receptor activation induced higher phospho-Thr34-DARPP-32 expression in sensitized mice than in non-sensitized or saline. The functionally hyperresponsiveness of D1 receptors in the nucleus accumbens is associated with an increased phospho-Thr34-DARPP-32 expression after D1 receptor activation. These data suggest that an enduring increase in the sensitivity of the dopamine D1 receptor intracellular pathway sensitivity represents a neurobiological correlate associated with the development of locomotor sensitization to ethanol.
在小鼠中，对乙醇行为敏化的发展存在明显的个体差异，乙醇的精神运动兴奋作用会逐渐增强。对乙醇行为反应的变异性与酒精偏好有关。在这里，我们研究了在乙醇致敏小鼠中观察到的D1受体功能高反应性是否会导致伏隔核（已知在药物强化中起作用的脑区）中中棘神经元的中央调节蛋白DARPP - 32的激活增加。瑞士韦伯斯特小鼠接受腹腔注射乙醇（2.2克/千克/天）或生理盐水，持续21天，并每周评估其运动活性。在接受乙醇治疗的小鼠中，运动活性水平最高的33%被归类为“致敏”，运动活性水平最低的33%被归类为“未致敏”。后者的运动水平与生理盐水处理的小鼠相似。不同亚组的小鼠接受伏隔核内注射生理盐水，48小时后，注射SKF - 38393，一种D1受体激动剂，剂量为0.1或1微克/侧。事实上，致敏小鼠在伏隔核中表现出D1受体的功能高反应性。乙醇治疗两周后，其他亚组在安乐死前20分钟接受全身注射生理盐水或SKF （10毫克/千克）。解剖伏隔核用于对总DARPP - 32和磷酸化苏氨酸34 - DARPP - 32表达进行蛋白质印迹分析。与未致敏或生理盐水处理的小鼠相比，D1受体激活在致敏小鼠中诱导了更高的磷酸化苏氨酸34 - DARPP - 32表达。伏隔核中D1受体的功能高反应性与D1受体激活后磷酸化苏氨酸34 - DARPP - 32表达增加有关。这些数据表明，多巴胺D受体细胞内途径敏感性的持久增加代表了与对乙醇运动致敏发展相关的神经生物学关联。
