Thompson Jason V, Sullivan Regina M, Wilson Donald A
Neurobehavioral Institute, Department of Zoology, University of Oklahoma, OK 73019, USA.
Brain Res. 2008 Mar 20;1200:58-65. doi: 10.1016/j.brainres.2008.01.057. Epub 2008 Feb 2.
Mother-infant attachment is facilitated in altricial rodents through unique neural mechanisms that include impaired neonatal fear conditioning until the time that pups first begin to leave the nest (sensitive period). Here, we confirmed the developmental emergence of odor fear conditioning in neonatal rat pups, and examined synaptic plasticity of inputs to the basolateral amygdala in vitro. Coronal slices through the amygdala were obtained from sensitive (<10 days) and post-sensitive (>10, <19 days) period pups. Field potentials were recorded in the basolateral amygdala in response to stimulation of either the external capsule (neocortical inputs) or fibers from the cortical nucleus of the amygdala (olfactory inputs). The effects of tetanic stimulation were examined in each pathway. In both pathways, tetanic stimulation induce significant long-term synaptic plasticity in post-sensitive period pups, but no significant plasticity in sensitive period pups incapable of learning odor aversions. GABA(A) receptor blockade in post-sensitive period slices reverts synaptic plasticity to sensitive period characteristics. The results suggest that sensitive period deficits in fear conditioning may be related to impaired amygdala synaptic plasticity and the immature state of GABAergic inhibition and/or its modulation in the neonatal amygdala.
在晚成啮齿动物中，母婴依恋通过独特的神经机制得以促进，这些机制包括在幼崽首次开始离巢（敏感期）之前新生期恐惧条件反射受损。在此，我们证实了新生大鼠幼崽气味恐惧条件反射的发育出现，并在体外研究了基底外侧杏仁核输入的突触可塑性。从处于敏感期（<10天）和敏感期后（>10天，<19天）的幼崽获取穿过杏仁核的冠状切片。在基底外侧杏仁核记录场电位，以响应对外侧囊（新皮质输入）或来自杏仁核皮质核的纤维（嗅觉输入）的刺激。在每条通路中检查强直刺激的效果。在两条通路中，强直刺激在敏感期后的幼崽中诱导出显著的长期突触可塑性，但在无法学习气味厌恶的敏感期幼崽中未诱导出显著的可塑性。在敏感期后切片中阻断GABA(A)受体可使突触可塑性恢复到敏感期特征。结果表明，恐惧条件反射中的敏感期缺陷可能与杏仁核突触可塑性受损以及新生杏仁核中GABA能抑制和/或其调节的不成熟状态有关。
