Effects Of Manganese (Mn²⁺) On The Neuromuscular Blockade Caused By Crotalus durissus terrificus And Bothrops jararacussu Venoms In Chick Biventer Cervicis Preparations

¹Bueno, L.G.F.; ¹Leite, G.B.; ¹Oshima-Franco, Y.; ¹Rodrigues-Simioni, L.

1 Depto. de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, SP.

Manganese (Mn²⁺) protects against the neurotoxicity of bothropstoxin-I (BthTX-I), a myotoxin from Bothrops jararacussu venom, in mouse isolated phrenic nerve-diaphragm preparations (Oshima-Franco et al., 2001 – Toxicon, 39, 77-85). In chick biventer cervicis preparations, there is complete recovery from the neuromuscular blockade caused by Mn²⁺ following washing of the preparation. In this work, we examined whether Mn²⁺ could protect against the neurotoxicity of C. d. terrificus and B. jararacussu venoms, both of which cause total, irreversible blockade in biventer cervicis preparations. The preparations were suspended in 5 ml of modified Krebs solution (composition, in mM: 118.1 NaCl, 4.8 KCl, 2.5 CaCl2, 1.2 MgSO4.7H2O, 11.1 glucose, 12.5 NaHCO3) aerated with 95%O2-5%CO2 (pH 7.4) and exposed to Mn²⁺ (0.66 mM) prior to incubation with C. d. terrificus (2.5 µg/mL) and B. jararacussu (200 µg/mL) venoms. Manganese prevented the characteristic blockade induced by B. jararacussu venom by 77.8 ± 11.7% (n=6), but only provided partial protection (23.8 ± 10.4%, n=6) against the neurotoxicity of C. d. terrificus venom. This ability of Mn²⁺ to discriminate between the effects of B. jararacussu and C. d. terrificus venoms suggests that Mn²⁺ may be useful for the pharmacological screening of venoms and toxins with different modes of action.

Support: CNPq and FAEP/UNICAMP.

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