Zhao Zuowei, Davis Michael
Department of Psychiatry and Behavioral Sciences, School of Medicine, Emory University, Atlanta, Georgia 30329, USA.
J Neurosci. 2004 Nov 17;24(46):10326-34. doi: 10.1523/JNEUROSCI.2758-04.2004.
The amygdala sends heavy and broad projections to the rostral midbrain including the periaqueductal gray (PAG), the deep layers of the superior colliculus/deep mesencephalic nucleus (deep SC/DpMe), and the lateral mesencephalic reticular formation (MRF) that in turn project to the nucleus reticularis pontis caudalis (PnC), an obligatory relay in the primary acoustic startle circuit. Chemical lesions or inactivation of these areas blocked fear-potentiated startle, suggesting that these areas serve as a relay between the amygdala and the PnC. In the present study, we tried to determine more precisely which of these sites were critical for fear-potentiated startle and the role of glutamate receptors in this site in mediating fear-potentiated startle. Local infusion of the non-NMDA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)-quinoxaline (NBQX) dose-dependently blocked fear-potentiated startle when infused into the deep SC/DpMe before testing but had no effect on baseline startle amplitude. NBQX did not block fear-potentiated startle when infused before training. The same dose of NBQX infused into the dorsal/lateral PAG, the lateral MRF, or the superficial layers of the SC did not affect fear-potentiated startle. However, NBQX tended to reduce contextual freezing when infused into the dorsal/lateral PAG. These findings suggest that the deep SC/DpMe is the site that serves as a critical output relay between the amygdala and the PnC in mediating fear-potentiated startle and that glutamatergic transmission is required for this action.
杏仁核向吻侧中脑发出大量广泛的投射，包括导水管周围灰质（PAG）、上丘深层/中脑深核（深层SC/DpMe）以及外侧中脑网状结构（MRF），这些结构转而投射到脑桥尾侧网状核（PnC），它是初级听觉惊吓回路中的一个必经中继站。对这些区域进行化学损伤或失活会阻断恐惧增强惊吓反应，这表明这些区域充当了杏仁核和PnC之间的中继站。在本研究中，我们试图更精确地确定这些位点中哪些对于恐惧增强惊吓反应至关重要，以及谷氨酸受体在该位点介导恐惧增强惊吓反应中的作用。在测试前向深层SC/DpMe局部注入非NMDA受体拮抗剂2,3 - 二羟基 - 6 - 硝基 - 7 - 氨磺酰基苯并(F)喹喔啉（NBQX），剂量依赖性地阻断了恐惧增强惊吓反应，但对基线惊吓幅度没有影响。在训练前注入NBQX则不会阻断恐惧增强惊吓反应。将相同剂量的NBQX注入背侧/外侧PAG、外侧MRF或SC的表层，并不影响恐惧增强惊吓反应。然而，当注入背侧/外侧PAG时，NBQX倾向于减少情境性僵住。这些发现表明，深层SC/DpMe是在介导恐惧增强惊吓反应中充当杏仁核和PnC之间关键输出中继站的位点，并且这种作用需要谷氨酸能传递。
