Differential activation of c-Fos in the paraventricular nuclei of the hypothalamus and thalamus following myocardial infarction in rats

Proto-oncogene c-Fos (c-Fos) is frequently used to detect a pathogenesis in central nervous system disorders. The present study examined changes in the immunoreactivity of c-Fos in the paraventricular nucleus of the hypothalamus (PVNH) and paraventricular nucleus of the thalamus (PVNT) following myocardial infarction (MI) in rats. Infarction in the left ventricle was examined by Masson's trichrome staining. Neuronal degeneration was monitored for 56 days after MI using crystal violet and Fluoro-Jade B histofluorescence staining. Changes in the immunoreactivity of c-Fos were determined using immunohistochemistry for c-Fos. The average infarct size of the left ventricle circumference was similar to 44% subsequent to MI. Neuronal degeneration was not detected in PVNH and PVNT following MI. c-Fos immunoreactive ((+)) cells were infrequently observed in the nuclei of the sham-group. However, the number of c-Fos(+) cells was increased in the nuclei following MI and peaked in the PVNH and PVNT at 3 and 14 days, respectively. The number of c-Fos(+) cells were comparable with the sham group at 56 days after MI. Therefore, MI may induce c-Fos immunoreactivity in PVNH and PVNT, this increase of c-Fos expression levels may be associated with the stress that occurs in the brain following MI.