Respiratory Muscle Injury Following Acute Monocled Cobra (Naja kaouthia) Envenoming: Histopathological Study in Rat Diaphragm

Clinical symptoms of monocled cobra (Naja kaouthia) envenoming include the paralysis of extraocular muscles, local tissue necrosis and death through respiratory failure. These neurotoxic outcomes are mainly due to the inhibitory action of postsynaptic neurotoxins to nicotinic acetylcholine receptors. However, injuries involving respiratory muscles have rarely been investigated. In this study, we determined the effect of N. kaouthia envenoming on morphological changes in the rat diaphragm. The efficacy of cobra monovalent antivenom in neutralising the histopathological effects of N. kaouthia venom was also evaluated. The intramuscular (i.m.) administration of N. kaouthia venom (2 mg/kg) caused skeletal muscle fibre atrophy and ruptures of myofibrils shown via a light microscope study. Transmission electron microscopy (TEM) revealed the zig-zagging of the Z-band, mitochondrial damages and degeneration of the synaptic fold of the neuromuscular junction following experimental cobra envenoming for 4 h. Intravenous administration of cobra antivenom at manufacturer-recommended doses diminished histopathological changes in the diaphragm following the administration of cobra venom. The expression of NF-kB and MuRF1 in the experimentally N. kaouthia-envenomed diaphragm indicated inflammation and tissue atrophy in the immunofluorescence analysis, respectively. In this study, we found that there were respiratory muscle injuries following N. kaouthia envenoming. The early administration of monovalent N. kaouthia antivenom is capable of neutralising neurotoxic outcomes following cobra envenoming.