逃避行为是使动物远离威胁的一组运动动作。虽然这些行为可以被定型,它们是灵活的,这对生存是有利的。1,2,3例如,逃逸概率取决于捕食风险和竞争动机,4,5,6,7,8,9,10,11和安全飞行需要连续调整轨迹,并且必须在适当的地点和时间终止。12,13,14,15,16这种程度的灵活性表明调制组件,像抑制网络,作用于控制本能逃逸的神经回路。17,18,19,20,21,22在小鼠中,摆脱迫在眉睫的威胁的决定是由中脑的前馈电路实现的,其中背侧导水管周围灰色(dPAG)中的兴奋性囊泡谷氨酸转运体2阳性(VGluT2)神经元计算逃逸起始和逃逸活力。23,24,25在这里,我们通过设置dPAG中的兴奋性来检验dPAG中的局部GABA能神经元控制逃逸行为的假设。dPAG逃逸网络。使用体外膜片钳和体内神经活动记录,我们发现,在没有突触输入的情况下,囊泡GABA转运体阳性(VGAT)dPAG神经元会音调激发动作电位,并且是VGluT2dPAG神经元抑制的主要来源。VGAT+dPAG细胞的活性在逃逸开始时短暂降低,在逃逸期间增加,在逃生终止时达到峰值。在威胁发作时传递刺激时,光遗传学上增加或减少VGATdPAG活性会改变逃逸的可能性,而在逃逸开始后传递时,则会改变逃逸的持续时间。我们得出的结论是,音调激发VGATdPAG神经元的活动为逃避启动设置了阈值,并控制了飞行动作的执行。
Escape behavior is a set of locomotor actions that move an animal away from threat. While these actions can be stereotyped, it is advantageous for survival that they are flexible.1,2,3 For example, escape probability depends on predation risk and competing motivations,4,5,6,7,8,9,10,11 and flight to safety requires continuous adjustments of trajectory and must terminate at the appropriate place and time.12,13,14,15,16 This degree of flexibility suggests that modulatory components, like inhibitory networks, act on the neural circuits controlling instinctive escape.17,18,19,20,21,22 In mice, the decision to escape from imminent threats is implemented by a feedforward circuit in the midbrain, where excitatory vesicular glutamate transporter 2-positive (VGluT2+) neurons in the dorsal periaqueductal gray (dPAG) compute escape initiation and escape vigor.23,24,25 Here we tested the hypothesis that local GABAergic neurons within the dPAG control escape behavior by setting the excitability of the dPAG escape network. Using in vitro patch-clamp and in vivo neural activity recordings, we found that vesicular GABA transporter-positive (VGAT+) dPAG neurons fire action potentials tonically in the absence of synaptic inputs and are a major source of inhibition to VGluT2+ dPAG neurons. Activity in VGAT+ dPAG cells transiently decreases at escape onset and increases during escape, peaking at escape termination. Optogenetically increasing or decreasing VGAT+ dPAG activity changes the probability of escape when the stimulation is delivered at threat onset and the duration of escape when delivered after escape initiation. We conclude that the activity of tonically firing VGAT+ dPAG neurons sets a threshold for escape initiation and controls the execution of the flight action.