INFLUENCE OF TEMPERATURE ON THE NEUROMUSCULAR BLOCKADE CAUSED BY THE VENOMS OF B. neuwiedi diporus, B. neuwiedi goyasensis AND B. neuwiedi paranaensis IN CHICK biventer cervicisPREPARATIONS

Abreu, V.A.(1), Leite, G.B. (1), Furtado, M.F. (2), Simioni, L.R.(1)

(1)Departamento de Farmacologia , Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP) Campinas, SP, Brasil, (2)Laboratório de Herpetologia, Instituto Butantan, São Paulo, SP, Brasil

Objectives: The influence of temperature on the neuromuscular activity of the venoms of  three subspecies of the pitviper Bothrops neuwiedi was studied using chick biventer cervicis muscle preparations. Methodology: Venoms were collected from specimens (diporus, goyasensis and paranaensis) by manual extraction and lyophilized. Male HY-LINE W36 chicks 4-8 days old  were used. After anesthesia with chloral hydrate (300 mg/kg, i.p.) the muscles were removed and mounted in a 5 ml organ bath (Ginsborgand Warriner, 1960) containing Krebs solution (mM): NaCl 118.7, KCl 4.7, CaCl₂ 1.88, KH₂PO₄ 1.17, MgSO₄ 1.17, NaHCO₃ 25.0, and glucose 11.65, pH 7.5, aerated with 95% O₂ and 5% CO₂. The experiments were done at 22°C or 37°C. Stimuli were given via a bipolar platinum ring electrode (0.1 Hz, 0.2 ms, 8 V, GRASS S48 stimulator) and the contractions were recorded on a Gould RS 3400 physiograph. Contractures to exogenous acetylcholine (ACh, 60 mM and 120 mM for 60 s) and KCl (20 mM for 180 s) were obtained to test for myotoxic and neurotoxic activities. After stabilization for 20 min,  ACh, KCl and venoms were added to the bath. ANOVA/MANOVA for repeated measures was used to examine the significance. Results:  B. n. diporus venom (50 g/ml) was more active in inducing neuromuscular blockade at 22ºC than the other venoms (62 ± 3.2% blockade after 120 min, n=3), B. n. goyasensis venom was more potent at 37ºC (58 ± 5% blockade after 120 min, n=3), whereas the B. n. paranaensis venom blockade (50 g/ml, n=3) was not significantly affected by temperature.  Changes in temperature did not affect the neuromuscular activity at high concentrations (100-200 g/ml). Conclusion: Only the activity of B. n. diporus venom was significantly altered by temperature, suggesting that the neurotoxic action was temperature-dependent at avian neuromuscular junctions.

Financial support: FAEP-UNICAMP.

CORRESPONDENCE TO:

Valdemir Aparecido de Abreu, Rua Arenque, 94, Vinhedo, SP, CEP: 13280.000, Brasil, Email: proabreubr@yahoo.com.br