Department of Biomedical Sciences, Neuroscience Section, and Centre of Excellence for the Neurobiology of Addictions, University of Cagliari, and Institute of Neuroscience, National Research Council, Cagliari Section, 09042 Monserrato Cagliari, Italy.
Horm Behav. 2012 Sep;62(4):505-14. doi: 10.1016/j.yhbeh.2012.08.010. Epub 2012 Sep 7.
Oxytocin (80 ng) induces yawning when injected into the caudal part of the ventral tegmental area, the hippocampal ventral subiculum and the posteromedial nucleus of the amygdala of male rats. The behavioural response occurred concomitantly with an increase in the concentration of extracellular dopamine and its main metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the dialysate obtained from the shell of the nucleus accumbens and of the prelimbic medial prefrontal cortex by means of intracerebral microdialysis. Both oxytocin responses were significantly reduced by d(CH₂)₅Tyr(Me)²-Orn⁸-vasotocin, a selective oxytocin receptor antagonist, injected in the above brain areas 15 min before oxytocin. Similar results were obtained by activating central oxytocinergic neurons originating in the paraventricular nucleus of the hypothalamus and projecting to the ventral tegmental area, the hippocampus and the amygdala, with the dopamine agonist apomorphine given at a dose that induces yawning when injected into the paraventricular nucleus. Since oxytocin is considered a key regulator of emotional and social reward that enhances amygdala-dependent, socially reinforced learning and emotional empathy, mesolimbic and mesocortical dopamine neurons play a key role in motivation and reward, and yawning in mammals is considered a primitive, unconscious form of empathy, the present results support the hypothesis that oxytocinergic neurons originating in the paraventricular nucleus of the hypothalamus and projecting to the above brain areas and mesolimbic and mesocortical dopaminergic neurons participate in the complex neural circuits that play a role in the above mentioned functions.
催产素（80ng）注射到雄性大鼠腹侧被盖区的尾侧部分、海马腹侧下托和杏仁核的后内侧核时，会引起哈欠。行为反应伴随着核仁accumbens 的壳和内侧前额叶皮层的预内侧前额叶皮层的细胞外多巴胺及其主要代谢物 3,4-二羟苯乙酸（DOPAC）浓度的增加，通过脑内微透析获得。在催产素之前 15 分钟，在上述脑区注射选择性催产素受体拮抗剂 d(CH₂)₅Tyr(Me)²-Orn⁸-vasotocin，可显著减少催产素反应。通过激活起源于下丘脑室旁核并投射到腹侧被盖区、海马和杏仁核的中枢催产素能神经元，并用多巴胺激动剂阿朴吗啡以引起室旁核注射时打哈欠的剂量给予，也可以得到类似的结果。由于催产素被认为是调节情绪和社会奖励的关键物质，它增强了杏仁核依赖性、社会强化学习和情感同理心，中脑边缘和中脑皮质多巴胺神经元在动机和奖励中起着关键作用，而哺乳动物的哈欠被认为是一种原始的、无意识的同理心形式，因此，本研究结果支持这样一种假设，即起源于下丘脑室旁核并投射到上述脑区和中脑边缘和中脑皮质多巴胺神经元的催产素能神经元参与了在上述功能中发挥作用的复杂神经回路。
