Learned helplessness (a model of depression-like state) was developed in rats by exposure to repeated inescapable electric stimulation and evaluated by the absence of attempts to escape when it could be performed. In randomly grouped outbred white rats, 37.5% animals after the above procedure meet the criterion of learned helplessness. On experimental day 14, the latent period and the number of applied electric shocks prior to the first escape to the safe compartment in rats with learned helplessness were significantly higher than in the control, but no significant differences in these parameters were observed on day 21. The Porsolt forced swimming test performed on days 14 and 21 revealed no differences from the control group. After the rats were divided into low- and high-active subgroups according to their open field behavior, 35% rats with learned helplessness were in the low-active subgroup group and 30% rats with learned helplessness were in the high-active subgroup. On day 14, the parameters of learned helplessness significantly surpassed the control levels only in the low-active subgroup. Only in rats with learned helplessness and low activity in the open field, the immobility time in the Porsolt test was longer than in control low-active rats. These findings attest to advisability of preliminary splitting of outbred animals by their open-field behavior into low- and high-active subgroups and the use of only animals for modeling learned helplessness.

中文翻译：

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远交白化大鼠形成抑郁样习得性无助状态的易感性评估

习得性无助（一种类似抑郁状态的模型）是通过暴露于反复不可避免的电刺激而在大鼠身上产生的，并通过在可以执行时没有试图逃脱来进行评估。在随机分组的远交白鼠中，经过上述程序后，37.5% 的动物符合习得性无助的标准。在实验第 14 天，习得性无助大鼠在第一次逃到安全隔间之前的潜伏期和施加的电击次数显着高于对照组，但在第 21 天观察到这些参数没有显着差异。在第 14 天和第 21 天进行的 Porsolt 强迫游泳测试显示与对照组没有差异。根据大鼠的旷场行为分为低活性亚组和高活性亚组后，35% 的习得性无助大鼠属于低活动亚组，30% 的习得性无助大鼠属于高活动亚组。在第 14 天，习得性无助的参数仅在低活跃亚组中显着超过控制水平。只有在野外习得性无助和低活动的大鼠中，Porsolt 试验中的不动时间比对照低活动大鼠长。这些发现证明了将远交动物通过开放场行为初步分为低活性和高活性亚组以及仅使用动物模拟习得性无助的可取性。习得性无助的参数仅在低活跃亚组中显着超过控制水平。只有在野外习得性无助和低活动的大鼠中，Porsolt 试验中的不动时间比对照低活动大鼠长。这些发现证明了将远交动物通过开放场行为初步分为低活性和高活性亚组以及仅使用动物模拟习得性无助的可取性。习得性无助的参数仅在低活跃亚组中显着超过控制水平。只有在野外习得性无助和低活动的大鼠中，Porsolt 试验中的不动时间比对照低活动大鼠长。这些发现证明了将远交动物通过开放场行为初步分为低活性和高活性亚组以及仅使用动物模拟习得性无助的可取性。