20.500.12556/RUL-159212 Comparative electrophysiological characterization of ammodytoxin A, a β-neurotoxin from the nose-horned viper venom, and its enzymatically inactive mutant Presynaptic- or β-neurotoxicity of secreted phospholipases A$_2$ (sPLA$_2$) is a complex process. For full expression of β-neurotoxicity, the enzymatic activity of the toxin is essential. However, it has been shown that not all toxic effects of a β-neurotoxin depend on its enzymatic activity, for example, the inhibition of mitochondrial cytochrome c oxidase. The main objective of this study was to verify whether it is possible to observe and study the phospholipase-independent actions of β-neurotoxins by a standard ex vivo twitch-tension experimental approach. To this end, we compared the effects of a potent snake venom β-neurotoxin, ammodytoxin A (AtxA), and its enzymatically inactive mutant AtxA(D49S) on muscle contraction of the mouse phrenic nerve-hemidiaphragm preparation. While AtxA significantly affected the amplitude of the indirectly evoked isometric muscle contraction, the resting tension of the neuromuscular (NM) preparation, the amplitude of the end-plate potential (EPP), the EPP half decay time and the resting membrane potential, AtxA(D49S) without enzymatic activity did not. From this, we can conclude that the effects of AtxA independent of enzymatic activity cannot be studied with classical electrophysiological measurements on the isolated NM preparation. Our results also suggest that the inhibition of cytochrome c oxidase activity by AtxA is not involved in the rapid NM blockade by this β-neurotoxin, but that its pathological consequences are rather long-term. Interestingly, in our experimental setup, AtxA upon direct stimulation reduced the amplitude of muscle contraction and induced contracture of the hemidiaphragm, effects that could be interpreted as myotoxic. snake venom ammodytoxin secreted phospholipase A$_2$ enzymatic activity cytochrome c oxidase ß-neurotoxicity snakes kačji strup encimska aktivnost strupene kače true false true Angleški jezik Slovenski jezik Članek v reviji 2024-07-03 14:20:03 2024-07-03 14:20:09 2024-07-13 03:53:27 0000-00-00 00:00:00 2024 0 0 6 str. Vol. 247, art. 107833 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 615:616-092:636.09 1879-3150 10.1016/j.toxicon.2024.107833 200247555 1-s2.0-S0041010124004057-main.pdf 1-s2.0-S0041010124004057-main.pdf 1 282F3E5A8D11BCC29F40211CDEF0D943 6b9fb43e3a56d0bf1c55d6f7ff5979b91589de52f1bf13718c810dea6680e02e e683e351-3936-11ef-a3da-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=187164 https://www.sciencedirect.com/science/article/pii/S0041010124004057 1 9618126b-3936-11ef-a3da-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=187163 Veterinarska fakulteta 0 0 0