<p>Conditioned taste aversion memory extinction temporally induces insular cortical BDNF release and inhibits neuronal apoptosis</p>

Abstract

Background: Memory extinction has been reported to be related to psychiatric disorders, such as post-traumatic stress disorder (PTSD). Secretion and synthesis of brain-derived neurotrophic factor (BDNF) have been shown to temporally regulate various memory processes via activation of tropomyosin-related kinase B (TrkB) receptors. However, whether memory extinction induces the synthesis and secretion of BDNF on the basis of its localization is not understood. In this study, we aim to investigate activity-dependent BDNF secretion and synthesis in the insular cortex (IC) in the setting of conditioned taste aversion (CTA) memory extinction. Materials and methods: Rats were subjected to CTA memory extinction and BDNF antibody (or the equal volume of vehicle) was microinjected into the IC immediately after the extinction testing. Real-time polymerase chain reaction and in situ hybridization were used to detect the gene expression of BDNF, NGF and NT4. The protein levels of BDNF were determined through the enzyme-linked immunosorbent assay. In addition, the levels of phosphorylated TrkB normalized to total TrkB were evaluated using immunoprecipitation and immunoblotting. c-Fos, total extracellular signal-regulated kinase (Erk), phosphorylated Erk, and apoptosis-related protein (caspase-3), were detected by Western blotting. Results: We found that blocking BDNF signaling within the IC disrupts CTA extinction, suggesting that BDNF signaling in the IC is necessary for CTA extinction. Increased expression levels of c-Fos indicate the induced neuronal activity in the IC during CTA extinction. In addition, temporal changes in the gene expression and protein levels of BDNF in the IC were noted during extinction. Moreover, we found that phosphorylation of TrkB increased prior to the enhanced BDNF expression, suggesting that CTA extinction induces rapid activity-dependent BDNF secretion in the IC. Finally, we found decreased expression of caspase-3 in the IC after CTA extinction. Conclusion: These results demonstrate that CTA memory extinction temporally induces the release and synthesis of BDNF in the IC and inhibits neuronal apoptosis.

Effects of stress contagion on anxiogenic‐ and orofacial inflammatory pain‐like behaviors with brain activation in mice

“…Those findings indicated that increases in the level of brain‐derived neurotrophic factor after exposure to social defeat stress might affect neural activities in the anterior cingulate cortex and insular cortex. Accordingly, blocking brain‐derived neurotrophic factor signaling within the insular cortex resulted in the reduction of c‐Fos expressions in the insular cortex and inhibited conditioned taste aversive responses in rats [64]. Our present results showed that stress contagion increased the brain‐derived neurotrophic factor level in the insular cortex but not in the anterior cingulate cortex, while both areas increased c‐Fos and FosB expressions.…”