The present study is planned to study the effect of immobilization stress on the cardiac muscle of adult male albino rats and the curative role of diazepam. The study was carried out on 80 albino rats; the animals were divided into eight groups: group 1 served as control rats; group 2 unstressed rats injected intraperitoneally daily with 0.1 mg/kg b.w. diazepam for 30 days; groups 3, 4, and 5 served as immobilized stressed-rats for 30 days (by restricting movement for 2 hr daily at different durations 5, 15, and 30 days, respectively); groups 6, 7, and 8 stressed rats treated daily with 0.1 mg/kg b.w. diazepam for 30 days. The histological study of the cardiac myofibres of the stressed-rats revealed disorganization of the muscle fibres, vacuolation of the sarcoplasm, pyknosis of the nuclei, congestion and dilatation of blood vessels in endomysium. The thickness of collagen fibres gradually increased and became compact dense in the stressed rats till 30 days, and they were more obvious around the blood vessels. The histochemical study demonstrated a marked reduction in the glycogen and protein contents of the cardiac muscle, and was time-dependent. The immunohistochemical study revealed that the rats stressed for different durations manifested the disappearance of the cytoskeletal desmin protein filaments at intercalated discs and Z-lines of the cardiac myofibres. Treatment with diazepam for 30 days to stressed rats demonstrated markedly improvements of the architecture of cardiac myofibres and restoration of the two main chemical components; glycogen and protein contents. Also, restoration of desmin in the cardiac myofibres was elucidated. The results indicated that diazepam is recommended to be used as a curative drug to improve the disturbances in the cardiomyocytes and myofibrils assembly caused under the effect of stress.
Key words: Cardiac muscle, Desmin, Diazepam, Histochemistry, Histology, Immunohistochemistry, Rat, Stress
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