RESUMEN
The neuromuscular effect of venoms is not a major clinical manifestation shared between rattlesnakes native to the Americas, which showed two different venom phenotypes. Taking into account this dichotomy, nerve muscle preparations from mice and chicks were used to investigate the ability of Crotalus atrox venom to induce in vitro neurotoxicity and myotoxicity. Unlike crotalic venoms of South America, low concentrations of C. atrox venom did not result in significant effects on mouse neuromuscular preparations. The venom was more active on avian nerve-muscle, showing reduction of twitch heights after 120â¯min of incubation with 10, 30 and 100⯵g/mL of venom with diminished responses to agonists and KCl. Histological analysis highlighted that C. atrox was myotoxic in both species of experimental animals; as evidenced by degenerative events, including edematous cells, delta lesions, hypercontracted fibers and muscle necrosis, which can lead to neurotoxic action. These results provide key insights into the myotoxicity and low neurotoxicity of C. atrox in two animal models, corroborating with previous genomic and proteomic findings and would be useful for a deeper understanding of venom evolution in snakes belonging to the genus Crotalus.
Asunto(s)
Venenos de Crotálidos/farmacología , Crotalus/fisiología , Músculo Esquelético/efectos de los fármacos , Fibras Nerviosas/efectos de los fármacos , Bloqueantes Neuromusculares/farmacología , Unión Neuromuscular/efectos de los fármacos , Animales , Pollos , Crotalus/crecimiento & desarrollo , Diafragma/citología , Diafragma/efectos de los fármacos , Diafragma/inervación , Diafragma/fisiología , Resistencia a Medicamentos , Técnicas In Vitro , Masculino , Ratones , Contracción Muscular/efectos de los fármacos , Músculo Esquelético/citología , Músculo Esquelético/inervación , Músculo Esquelético/fisiología , Fibras Nerviosas/fisiología , Unión Neuromuscular/fisiología , América del Norte , Especificidad de Órganos , Músculos Paraespinales/citología , Músculos Paraespinales/efectos de los fármacos , Músculos Paraespinales/inervación , Músculos Paraespinales/fisiología , Nervio Frénico/citología , Nervio Frénico/efectos de los fármacos , Nervio Frénico/fisiología , Especificidad de la Especie , Nervios Espinales/citología , Nervios Espinales/efectos de los fármacos , Nervios Espinales/fisiologíaRESUMEN
The parapyramidal (ppy) region targets primarily the intermediolateral cell column and is probably involved in breathing and thermoregulation. In the present study, we tested whether ppy serotonergic neurons respond to activation of central and peripheral chemoreceptors. Bulbospinal ppy neurons (n=30) were recorded extracellularly along with the phrenic nerve activity in urethane/α-chloralose-anesthetized, paralyzed, intact (n=7) or carotid body denervated (n=6) male Wistar rats. In intact animals, most of the ppy neurons were inhibited by hypoxia (n=14 of 19) (8% O2, 30s) (1.5 ± 0.03 vs. control: 2.4 ± 0.2 Hz) or hypercapnia (n=15 of 19) (10% CO2) (1.7 ± 0.1 vs. control: 2.2 ± 0.2 Hz), although some neurons were insensitive to hypoxia (n=3 of 19) or hypercapnia (n=4 of 19). Very few neurons (n=2 of 19) were activated after hypoxia, but not after hypercapnia. In carotid body denervated rats, all the 5HT-ppy neurons (n=11) were insensitive to hypercapnia (2.1 ± 0.1 vs. control: 2.3 ± 0.09 Hz). Biotinamide-labeled cells that were recovered after histochemistry were located in the ppy region. Most labeled cells (90%) showed strong tryptophan hydroxylase immunocytochemical reactivity, indicating that they were serotonergic. The present data reveal that peripheral chemoreceptors reduce the activity of the serotonergic premotor neurons located in the ppy region. It is plausible that the serotonergic neurons of the ppy region could conceivably regulate breathing automaticity and be involved in autonomic regulation.