Study of social defeat stress effect on nociceptive behavior in mice and neurobiological mechanisms associated

Author(s)

Marco Oreste Finocchio Pagliusi Junior

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2016-04-02

Examining board members

Carlos Amílcar Parada; Silvana Chiavegatto; Maria Andréia Delbin

• Advisor: Carlos Amílcar Parada; César Renato Sartori

Abstract

Despite the pain is not one of the symptoms for the depression diagnosis, epidemiological studies indicate a close association between depressive disorder and chronic pain. This is evidenced by the clinical observation that patients with depression have high prevalence of chronic pain and, at the same time, patients suffering from chronic pain are also often diagnosed with depressive disorders. Several clinical and biological characteristics are shared between pain and depression, and various neuroanatomical structures, neural circuits and neurotransmitter systems exhibit similar changes in those two conditions. In Social Defeat Stress animal model, recently developed, intruder mice are exposed to resident mice from a more aggressive and more physically robust strain, experiencing brief periods of physical aggression followed by longer periods of sensory contact. The defeated mice may display a number of physiological and behavioral depressive-like characteristics, and then they are considered susceptible; furthermore, some defeated mice may not display these characteristics, and then they are considered resilient. However, there is no data regarding the pain sensibility in such animals. Thus, this study aimed to investigate the behavioral response to nociceptive stimulation, through Von Frey and capsaicin test, in mice submitted to the Social Defeat Stress model. For this, three experimental groups were established: Control group, where the intruder mice were paired with mice of the same strain; susceptible group, and, finally, resilient group. Our data showed that susceptible mice exhibited greater pain intensity in both tests when compared to both control and resilient mice. Furthermore, we found that the resilient mice showed an intermediate nociceptive threshold compared to the other two groups (susceptible and control), presenting, therefore, resiliency also to the decreasing of the nociceptive threshold. In addition, the Social Defeat Stress increased BDNF expression in the VTA of susceptible group, but not in the resilient group, in comparison with de control group. The protein levels of BDNF isoforms were evaluated in the NAc; we found an decreased of the mature isoform of BDNF protein in the defeated groups in comparison with the control groups, an increase in the truncated isoform of BDNF in the susceptible group and no differences in the precursor isoform of BDNF. These results suggest the existence of a common process of neuronal plasticity underlying both chronic pain and stress-induced depressive disorder. Our experimental data corroborate the comorbidity between pain and depressive disorder frequently observed in the clinic (AU)

• FAPESP's process: 13/09749-4 - Study of social defeat stress effects on nociceptive behavior in mice and neurobiological mechanisms associated
• Grantee: Marco Oreste Finocchio Pagliusi Junior
• Support Opportunities: Scholarships in Brazil - Master