Involvement of activated astrocyte and microglia of locus coeruleus in cardiac pain processing after acute cardiac injury

Abstract

Objective: It is still not known whether the glial cell activation of locus coeruleus (LC) is involved in the neurophysiologic mechanism of the acute phase of heart disease. The aim of this study was to investigate whether the glial cell activation of LC responds to acute cardiac injury (ACI).

Methods: In this study, ACI was established by intramyocardial injection of formalin. Afterward, we analysed c-Fos, OX42, GFAP and P2X₄R expression levels in the LC of the rats by immunofluorescence staining or Western blot analysis.

Results: There was no significant difference in the levels of these markers in the LC between the normal control and the sham-operated groups. Following ACI, up-regulation of GFAP, OX42 and P2X₄R expression levels were observed in locus coeruleus of the rats. The peak expression time was at hour 24. P2X₄R was colocalized with OX42 in activated microglias, but not with GFAP in activated astrocytes. Compared with the control group, the ACI group showed a high expression level of c-Fos at hour 1 with a peak expression level at hour 2.

Conclusion: The results showed that LC glia cells, like neurons, could sensitively respond to cardiovascular nociception induced by ACI at different time points. Results of this study may provide insights into the role of glial activation in response to ACI and may represent a potential strategy for investigation of neurophysiologic mechanism of cardiac pain.

Keywords:

• ACUTE CARDIAC INJURY
• LOCUS COERULEUS
• OX42
• GFAP
• P2X4 RECEPTOR