The oxytocin (OXT) and dopamine systems synergistically facilitate striatal reactivity. Abnormal striatal activation has repeatedly been observed in patients with bipolar disorder (BD); however, such abnormality remains unclear in BD II. Here we aimed to investigate whether the corticostriatal connectivity was altered and the possible relationships among corticostriatal connectivity, OXT, and dopamine systems in BD II. Twenty-five BD II patients, as defined by the DSM-V, and 29 healthy controls (HC) were enrolled in this study. Plasma OXT was measured and striatal dopamine transporter (DAT) availability was assessed using [^99mTc]TRODAT-1 single-photon emission computed tomography (SPECT). Brain network functional connectivity (FC) was measured during the resting-state using functional magnetic resonance imaging, and the dorsal caudate (DC) was selected as the seed region. The results showed that the OXT level was significantly lower in the BD II patients, while the striatal DAT availability was not significantly different between the BD II and HC groups. The BD II patients exhibited significantly lower FC between the DC and the executive control network (dorsolateral prefrontal, anterior cingulate cortex, and posterior parietal cortex) as compared with the HC. Only observed in HC, the DC-posterior parietal cortex FC was negatively correlated with the OXT level and striatal DAT availability. Our findings in the HC support a model in which the OXT and dopamine systems act in tandem to regulate corticostriatal circuitry, while the synergistic interaction was perturbed in BD II. Taken together, these results implied a maladaptive neuroplasticity in BD II.

催产素 (OXT) 和多巴胺系统协同促进纹状体反应。在双相情感障碍（BD）患者中反复观察到异常的纹状体激活；然而，这种异常在 BD II 中仍不清楚。在这里，我们旨在调查 BD II 中皮质纹状体连接是否发生改变以及皮质纹状体连接、OXT 和多巴胺系统之间可能存在的关系。由 DSM-V 定义的 25 名 BD II 患者和 29 名健康对照 (HC) 参加了本研究。测量血浆 OXT 并使用 [ ^{99m ] 评估纹状体多巴胺转运蛋白 (DAT) 可用性}Tc]TRODAT-1 单光子发射计算机断层扫描 (SPECT)。使用功能性磁共振成像在静息状态下测量脑网络功能连接（FC），并选择背尾状核（DC）作为种子区域。结果显示，BD II 组患者的 OXT 水平显着降低，而 BD II 组和 HC 组之间纹状体 DAT 可用性没有显着差异。与 HC 相比，BD II 患者在 DC 和执行控制网络（背外侧前额叶、前扣带皮层和后顶叶皮层）之间的 FC 显着降低。仅在 HC 中观察到，DC-后顶叶皮层 FC 与 OXT 水平和纹状体 DAT 可用性呈负相关。我们在 HC 中的发现支持一个模型，其中 OXT 和多巴胺系统协同作用以调节皮质纹状体电路，而协同作用在 BD II 中受到干扰。总之，这些结果暗示了 BD II 中的适应不良的神经可塑性。