Abstract
The amygdala is an important structure contributing to socio-emotional behavior. However, the role of the amygdala in autism remains inconclusive. In this study, we used the 28–35 days valproate (VPA)-induced rat model of autism to observe the autistic phenotypes and evaluate their synaptic characteristics in the lateral nucleus (LA) of the amygdala. The VPA-treated offspring demonstrated less social interaction, increased anxiety, enhanced fear learning and impaired fear memory extinction. Slice preparation and electrophysiological recordings of the amygdala showed significantly enhanced long-term potentiation (LTP) while stimulating the thalamic-amygdala pathway of the LA. In addition, the pair pulse facilitation (PPF) at 30- and 60-ms intervals decreased significantly. Whole-cell recordings of the LA pyramidal neurons showed an increased miniature excitatory postsynaptic current (EPSC) frequency and amplitude. The relative contributions of the AMPA receptor and NMDA receptor to the EPSCs did not differ significantly between groups. These results suggested that the enhancement of the presynaptic efficiency of excitatory synaptic transmission might be associated with hyperexcitibility and enhanced LTP in LA pyramidal neurons. Disruption of the synaptic excitatory/inhibitory (E/I) balance in the LA of VPA-treated rats might play certain roles in the development of behaviors in the rat that may be relevant to autism. Further experiments to demonstrate the direct link are warranted.
Highlights
In humans, the amygdala is sensitive to environmental signs of emotional and social significance [1,2]
A neuroimaging study found that the volume of the amygdala and cortical areas with amygdala connectivity correlates with the size and complexity of social networks in adult humans [9]
The results indicated that the VPA-treated rat model presented social, anxiety and fear behaviors that may be relevant to some of the behavioral symptoms exhibited in individuals with autism spectrum disorder (ASD)
Summary
The amygdala is sensitive to environmental signs of emotional and social significance [1,2]. It could modulate emotional memory storage and drive autonomic response [3]. Emotional learning of social conventions through the amygdala may contribute to socio-emotional regulation [4,5,6,7]. Social status has been found to be linked to the degree of amygdala activation [8]. The laterally-situated nuclei (the lateral, lateral basal, mesial basal, and accessory basal nuclei) appear to contain neurons responsive to sensory social cues [1,2,12,13]. Most functional imaging studies reveal the amygdala function as a whole but do not distinguish the separate roles of specific nuclei in humans [14]
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