Neuromuscular blocking action of the Theraphosa blondii spider venom

Abstract

In 1919, Houssay and Negrete reported that venoms of Theraphosidae spiders induced neuromuscular blockade. In 1993, a purified toxin from Grammostola spider venom was found to block the P-type voltage-dependent calcium channel (VDCC), causing neuromuscular blockade. We studied the mode of action of Theraphosa blondii venom, a large Theraphosidae spider from Northern Brazil, Venezuela, and The Guyanas in mouse phrenic nerve-diaphragm preparation. This venom elicited a partially reversible neuromuscular blockade and did not depress directly evoked twitches or alter the membrane potential. Neostigmine produced only a poor antagonistic effect on partially blocked diaphragms. However, completely blocked miniature endplate potentials (m.e.p.ps) were reverted by neostigmine. These results can be explained by the presence of toxins in the venom that interact with the endplate receptor at the acetylcholine sites (curaremimetic toxins) and toxins that inhibit the P-type voltage-dependent calcium channel (VDCC) (omega -toxins). This study shows that Theraphosidae venoms, especially those of the Theraphosa blondii, are a source of curaremimetic toxins and omega -toxins of possible interest as tools in bioscientific research

Brazilian Theraphosidae: a toxicological point of view

“…In 2002, Fontana et al [14] studied the mode of action of T. blondi venom in mouse phrenic nerve-diaphragm preparation. The venom caused partial and reversible neuromuscular blockage, not depressing spasms caused by direct stimulation or altering the membrane potential.…”

“…The blockage caused by the venom suffered a weak antagonistic effect by neostigmine, which however, completely blocked the venom activity in miniature end plate potentials. The authors suggested the presence of toxins that interact with the terminal plaque receptor at the sites of acetylcholine as curare mimetic toxins, and toxins that inhibit the type P voltage-dependent calcium channel as an explanation for the different effects caused by the interaction of neostigmine with the venom [14].…”

Purificação e caracterização de hialuronidase da peçonha da caranguejeira Vitalius dubius (Araneae, Theraphosidae)

“…Diversas atividades biológicas têm sido relatadas nas peçonhas de caranguejeiras, tais como Heteroscodra, Stromatopelma e Poecilotheria (8,9). Em relação às espécies brasileiras, Fontana et al (10) relataram que a peçonha da aranha Theraphosa leblondi produz bloqueio neuromuscular parcialmente reversível em preparações nervo frênico-diafragma de rato, talvez através da ação de toxinas que interagem com os receptores nicotínicos da acetilcolina ou de toxinas que inibem os canais de cálcio dependentes de voltagem. Posteriormente, Kalapothakis et al (11) mostraram que a peçonha da aranha Lasiodora sp.…”