Rationale and objective

This study was undertaken to assess the modulating effects of (1) pre-exposure to repeated social disruption and (2) group testing on writhing associated with visceral pain induced by intraperitoneal administration of acetic acid.

Materials and methods

Six consecutive days of social disruption were used to prime for stress, while group testing referred to 3 mouse cage-mates receiving the acetic acid–induced writhing test as a group.

Results

Social disruption–induced stress-pre-exposed mice displayed a greater number acid-induced writhes compared to mice not receiving the pre-exposure. However, mice displayed fewer acid-induced writhes in a triad group vs. individually, suggesting group-mediated writhing-reducing effects. Likewise, group testing prevented the stress pre-exposure escalation in acid-induced writhes. Additional studies revealed that the stress-pre-exposed mice had increased expression in accumbal TRPV1 receptors. Systemic (0.25 mg/kg) and bilateral intra-accumbal (0.2 ng/0.2 µl/side) administration of SB366791, a TRPV1 receptor antagonist, reliably prevented the stress pre-exposure escalation in acid-induced writhing; SB366791 treatment alone did not affect acid-induced writhing, stress pre-exposure anxiety-like behavior, or the group testing effects. Furthermore, lower neuronal activation was found in the medial septal nucleus in group vs. individual tested mice. Intra-medial septum (0.2 µg/0.5 µl) infusion with bicuculline, a GABAA receptor antagonist, effectively prevented group-mediated writhing-reducing effects, but not individual acid-induced writhing effects.

Conclusions

These findings suggest that social disruption–induced stress pre-exposure may upregulate accumbal TRPV1 receptor expression and consequently aggravate acid-induced writhing. Group testing prevents such stress pre-exposure escalation of acid-induced writhing most likely by strengthening the GABAergic inhibition on local neural activity in the medial septum.

中文翻译：

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社会破坏引起的压力暴露前加剧，而同种的存在减少，醋酸引起的扭动

理由和目标

本研究旨在评估 (1) 预先暴露于反复社会破坏和 (2) 小组测试对与腹膜内施用乙酸引起的内脏疼痛相关的扭体的调节作用。

材料和方法

连续六天的社会混乱被用来为压力做好准备，而群体测试则是指 3 只接受醋酸诱导扭体测试的老鼠作为一个群体。

结果

与未接受预暴露的小鼠相比，社会破坏引起的压力预暴露小鼠表现出更多的酸引起的扭体。然而，与单独相比，小鼠在三联组中表现出较少的酸诱导扭体，这表明群体介导的扭体减少作用。同样，小组测试防止了酸引起的扭体的压力暴露前升级。其他研究表明，应激预暴露小鼠在累积的 TRPV1 受体中的表达增加。SB366791（一种 TRPV1 受体拮抗剂）的全身（0.25 毫克/千克）和双侧腋窝内（0.2 纳克/0.2 微升/侧）给药可靠地防止了酸引起的扭体中的压力暴露前升级；SB366791 单独治疗不影响酸引起的扭体、压力暴露前焦虑样行为或组测试效果。此外，在组与个体测试小鼠的内侧间隔核中发现较低的神经元激活。用荷包牡丹碱（一种 GABAA 受体拮抗剂）内膜内隔 (0.2 µg/0.5 µl) 输注可有效防止组介导的减少扭体效应，但不能有效防止个体酸引起的扭体效应。

结论

这些发现表明，社会破坏引起的压力预暴露可能会上调累积的 TRPV1 受体表达，从而加剧酸引起的扭体。组测试通过加强 GABA 能抑制内侧隔中的局部神经活动来防止酸引起的扭体的这种压力暴露前升级。