Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
Neuropsychopharmacology. 2023 Aug;48(9):1338-1346. doi: 10.1038/s41386-022-01518-8. Epub 2022 Dec 15.
Long-term memory formation leads to enduring alterations in synaptic efficacy and neuronal responses that may be created by changes in neuronal morphology. We show that fear conditioning leads to a long-lasting increase in the volume of the primary and secondary dendritic branches, but not of distal branches, of neurons located at the basolateral amygdala (BLA). The length of the dendritic branches is not affected by fear conditioning. Fear conditioning leads to an enduring increase in the length and volume of dendritic spines, especially in the length of the spine neck and the volume of the spine head. Fear conditioning does not affect dendritic spine density. We further reveal that activation of Rac1 in BLA during fear conditioning impairs long-term auditory, but not contextual, fear conditioning memory. Activation of Rac1 during fear conditioning prevents the enduring increase in the dendritic primary branch volume and dendritic spines length and volume. Rac1 activation per se has no effect on neuronal morphology. These results show that fear conditioning induces changes known to reduce the inhibition of signal propagation along the dendrite and the increase in synaptic efficacy whereas preventing these changes, by Rac1 activation, impairs fear memory formation.
长期记忆的形成导致突触效能和神经元反应的持久改变，这些改变可能是由神经元形态的变化引起的。我们发现，恐惧条件反射会导致位于基底外侧杏仁核（BLA）的神经元的初级和次级树突分支的体积长期增加，但不包括远端分支。恐惧条件反射不会影响树突分支的长度。恐惧条件反射会导致树突棘的长度和体积的持久增加，特别是在棘突颈部的长度和棘突头部的体积上。恐惧条件反射不会影响树突棘密度。我们进一步揭示，在恐惧条件反射过程中，BLA 中的 Rac1 的激活会损害长期的听觉，但不会损害上下文的恐惧条件反射记忆。在恐惧条件反射过程中激活 Rac1 会阻止树突初级分支体积和树突棘长度和体积的持久增加。Rac1 的激活本身对神经元形态没有影响。这些结果表明，恐惧条件反射会诱导已知的改变，这些改变会减少信号沿着树突传播的抑制，并增加突触效能，而通过 Rac1 的激活来阻止这些改变会损害恐惧记忆的形成。
