Indeed, time-course experiments indicated a negative correlation between the extent of contracture to exogenous ACh and the degree of neuromuscular blockade (data not shown), find more further suggesting a role for nicotinic receptor inactivation in the resulting blockade. The experiments with d-Tc indicated that this compound protected the twitch-tension response against the irreversible blockade

caused by the venom, without protecting the responses to exogenous ACh and KCl (compare Fig. 1B2 and 1B3). This discrepancy in the protection by d-Tc probably reflects the presence of junctional and extra-junctional ACh nicotinic receptors, with the latter being more susceptible to inhibition by venom toxins than the former, as also suggested for some coral snake venoms, e.g., Micrurus pyrrhocryptus ( Camargo et al., 2011). The ∼60% reduction in the responses

to KCl seen with venom concentrations of 10 μg/ml and 100 μg/ml, together with the marked increase in CK release at the end of the incubations and the morphometric results indicated that B. alcatraz venom was also myotoxic, and this muscle damage could contribute to the overall neuromuscular blockade. Bothrops venoms contain PLA2 Nutlin-3a clinical trial myotoxins ( Moura-Da-Silva et al., 1991) that show varying levels of PLA2 activity ( Lomonte et al., 2003). These myotoxins caused edema and inflammation ( Teixeira et al., 2003), muscle necrosis ( Gutiérrez and Ownby, 2003), lethality and neuromuscular blockade in vitro ( Gallacci and Cavalcante,

2010). Angiogenesis inhibitor In contrast to certain Bothrops venoms, such as B. jararacussu, and B. moojeni ( Moura-Da-Silva et al., 1991), B. alcatraz venom had low PLA2 activity. PLA2 myotoxins have not yet been isolated from this venom and it is unclear to what extent PLA2 activity contributes to the neuromuscular blockade seen here. Bothropic antivenom neutralized the neuromuscular blockade by B. alcatraz venom (10 μg/ml), but only when used in a proportion 15 times higher than that recommended by the manufacturer. This finding agrees with Furtado (2005) who found that this same antivenom was weaker at neutralizing the hemorrhagic and lethal activity of B. alcatraz venom compared to its efficacy against B. jararaca venom (which is included in the venom pool used in the immunization protocol). The reason for the limited neutralization seen with 100 μg of venom/ml when the antivenom:venom ratio was the same as that used with the lower venom concentration is unclear. Perhaps at the higher venom concentration other venom components, present at too low a concentration to affect neuromuscular transmission with 10 μg of venom/ml, are now involved. These components may not be adequately neutralized by the antivenom, which is raised against a pool of venoms from mainland Bothrops species and does not include B. alcatraz. In conclusion, B.