Foundation for Advancement of International Science, Tsukuba, Ibaraki 305-0821, Japan.
Neurosci Lett. 2013 Mar 1;536:85-9. doi: 10.1016/j.neulet.2012.12.054. Epub 2013 Jan 11.
Positive emotional states have been reported to modify human resilience to fear and anxiety, but few animal models are available to elucidate underlying mechanisms. In the current study, we examined whether 2 weeks of tickling, which is considered to evoke positive emotions, alters conditioned fear and hormonal reactions in Fischer rats. We conditioned rats to fear an auditory tone which was initially paired with a mild foot-shock (0.2mA), and retention test was conducted 48h and 96h after conditioning. During these tests, we found that prior tickling treatment significantly diminished fear-induced freezing. To examine the effects of tickling on sympatho-adrenal and hypothalamic-pituitary-adrenal responses associated with conditioned fear, we measured plasma catecholamine and corticosterone levels in the retention test 96h after conditioning. The plasma catecholamine concentration of non-tickled rats was higher than basal levels, whereas tickled rats showed significantly reduced concentrations of both plasma adrenaline and noradrenaline. No significant differences in plasma corticosterone levels were observed between tickled and non-tickled rats. These results suggest that repeated exposure to tickling can modulate fear-related behavior and sympatho-adrenal stress responses.
积极的情绪状态被报道可以改变人类对恐惧和焦虑的适应能力，但很少有动物模型可以阐明潜在的机制。在本研究中，我们研究了 2 周的挠痒是否可以改变 Fischer 大鼠的条件性恐惧和激素反应，因为挠痒被认为可以引起积极的情绪。我们使大鼠对听觉声音产生恐惧，该声音最初与轻度足部电击（0.2mA）配对，然后在条件反射后 48 小时和 96 小时进行保留测试。在这些测试中，我们发现，预先的挠痒处理显著减少了恐惧引起的冻结。为了研究挠痒对与条件性恐惧相关的交感肾上腺和下丘脑-垂体-肾上腺反应的影响，我们在条件反射后 96 小时的保留测试中测量了血浆儿茶酚胺和皮质酮水平。未挠痒大鼠的血浆儿茶酚胺浓度高于基础水平，而挠痒大鼠的血浆肾上腺素和去甲肾上腺素浓度明显降低。挠痒和未挠痒大鼠的血浆皮质酮水平无显著差异。这些结果表明，反复暴露于挠痒可以调节与恐惧相关的行为和交感肾上腺应激反应。
