C-Fos mapping of brain regions activated by multi-modal and electric foot shock stress

Xiaoxiao Lin,Christy A Itoga,Sharif Taha,Ming H Li,Ryan Chen,Kirolos Sami,Fulvia Berton,Walter Francesconi,Xiangmin Xu

doi:10.1016/j.ynstr.2018.02.001

Abstract

Real-world stressors are complex and multimodal, involving physical, psychological, and social dimensions. However, the brain networks that mediate stress responses to these stimuli need to be further studied. We used c-Fos mapping in mice to characterize brain circuits activated by exposure to a single episode of multimodal stress (MMS), and compared these to circuits activated by electric foot shocks (EFS). We focused on characterizing c-Fos activity in stress-relevant brain regions including the paraventricular nucleus (PVN) of the hypothalamus and the bed nucleus of the stria terminalis (BNST). We also assessed stress-induced activation of CRH-positive neurons in each of these structures. MMS and EFS activated an overlapping network of brain regions with a similar time course. c-Fos expression within the PVN and the BNST peaked 30–60 min after exposure to both MMS and EFS, and returned to baseline levels within 24 h. Quantification of c-Fos expression within BNST subregions revealed that while c-Fos expression peaked in all subregions 30–60 min after MMS and EFS exposure, the neuronal density of c-Fos expression was significantly higher in the dorsomedial and ventral BNST relative to the dorsolateral BNST. Our preliminary assessment indicated that a great majority of MMS or EFS-activated neurons in the PVN were CRH-positive (>87%); in contrast, about 6–35% of activated neurons in the BNST were CRH-positive. Our findings indicate that both MMS and EFS are effective at activating stress-relevant brain areas and support the use of MMS as an effective approach for studying multidimensional stress in animal models. The results also reveal that the PVN and BNST are part of a common neural circuit substrate involved in neural processing related to stress.

Highlights

Generating appropriate behavioral, autonomic, and affective responses to stress-inducing stimuli, which signal potential danger in the environment, is critical for animals’ survival
Mice were subjected to single episodes of either electric foot shock (EFS) or multi-modal stress (MMS) consisting of concurrent bright light, unpredictable loud noise, jostling and restraint (Fig. 1)
To assess hormonal stress responses, plasma corticosterone levels of the EFS and MMS groups were measured at 30–60 min, 24 h, and 1 week after stress treatment, and compared to unstressed control mice (Fig. 2)

Summary

Introduction

Generating appropriate behavioral, autonomic, and affective responses to stress-inducing stimuli, which signal potential danger in the environment, is critical for animals’ survival. These responses might be highly dependent on the characteristics of stressors (Katz et al, 1981; McEwen, 2007). It is important to further understand and compare neural circuit activation by stressful stimuli with distinct characteristics using animal models. Previous studies of animal models suggest that multi-modal stress (MMS) leads to distinct patterns of neural activation compared with unimodal restraint stress. Exposing mice to MMS involving concurrent delivery of bright light, unpredictable noise, restraint, and jostling led to severe memory impairments and decreased synaptic density in the dorsal CA1 (Maras et al, 2014); neither of these changes were observed after exposure to a comparable period of restraint stress or loud noise alone

Methods

Results

Discussion

Conclusion