Neuromuscular activity of Bothrops neuwiedi pauloensis snake venom in mouse nerve-muscle preparations

Abstract

ABSTRACT:The pharmacological effects of Bothrops neuwiedi pauloensis venom on mouse phrenic nerve-diaphragm (PND) preparations were studied. Venom (20 µg/ml) irreversibly inhibited indirectly evoked twitches in PND preparations (60 ± 10% inhibition, mean ± SEM; p<0.05; n=6). At 50 µg/ml, the venom blocked indirectly and directly (curarized preparations) evoked twitches in mouse hemidiaphragms. In the absence of Ca 2+ , venom (50 µg/ml), produced partial blockade only after an 80 min incubation, which reached 40.3 ± 7.8% (p<0.05; n=3) after 120 min. Venom (20 µg/ml) increased (25 ± 2%, p<0.05) the frequency of giant miniature end-plate potentials in 9 of 10 end-plates after 30 min and the number of miniature end-plate potentials which was maximum (562 ± 3%, p<0.05) after 120 min. During the same period, the resting membrane potential decreased from -81 ± 1.4 mV to -41.3 ± 3.6 mV 24 fibers; p<0.01; n=4) in the end-plate region and from -77.4 ± 1.4 to -44.6 ± 3.9 mV (24 fibers; p<0.01; n=4) in regions distant from the end-plate. These results indicate that B. n. pauloensis venom acts primarily at presynaptic sites. They also suggest that enzymatic activity may be involved in this pharmacological action.

Purification and n-terminal sequencing of two presynaptic neurotoxic PLA2, neuwieditoxin-I and neuwieditoxin-II, from Bothrops neuwiedi pauloensis (jararaca pintada) venom

“…In previous reports, the neuromuscular blocking effect of BNP venom in BCP and MPND was temperature and Ca 2+ -dependent and this fact also indicated that enzymatic activity is necessary for neuromuscular action (4,12). The neuromuscular blocking effect of the fraction corresponding to peak 3, from the molecular exclusion step, which showed PLA 2 activity and revealed NeuTX-I and NeuTX-II after reversephase HPLC, was temperature-dependent, indicating that its neurotoxicity may require enzymatic activity, as suggested for the venom (4).…”

“…The presence of a presynaptic PLA 2 in B. n. pauloensis venom was expected, since several reports had already indicated that this venom had presynaptic neurotoxicity (4,5,12,44,53). NeuTX-I and NeuTX-II have Gly-30 and Gly-32, but Lys-49 toxins such as BnSP-7, a myotoxic PLA 2 from B. n. pauloensis venom (13,32,46), besides bothropstoxin-I, piratoxins, Basp-II and Bneu, have Leu-32 (L-32) for Gly-32.…”

“…Although neurotoxicity has been demonstrated in vitro (4,5,9,10,12,44,46,53) and in vivo (9, 53) for various Bothrops venoms, there is no conclusive evidence for such an effect after snakebite in humans. In vitro, the neurotoxicity of BNP venom is mainly presynaptic (4,5,12,44,53), although its potency varies from sample to sample (5).…”

“…In vitro, the neurotoxicity of BNP venom is mainly presynaptic (4,5,12,44,53), although its potency varies from sample to sample (5).…”

“…More recently, we have observed that the presynaptic neurotoxicity of BNP on MPND is Ca 2+ -dependent and accompanied by a pronounced increase in the frequency of mepps and the presence of giant mepps (12).…”