Poster 211 - Telocinobufagin, a bufodienolide found in Bufo Paracnemis toad venom, induces reversible

Poster 211. Congresso da Sociedade Brasileira de Toxinologia, 8., Symposium of the Pan American Section of the International Society on Toxinology, 8., 2004, Angra dos Reis, Brasil. Abstracts... J. Venom. Anim. Toxins incl.Trop. Dis., 2004, 10, 3, p.570.

Telocinobufagin, A Bufodienolide Found In Bufo Paracnemis Toad Venom, Induces Reversible Conduction Block In Isolated Rat Sciatic Nerve

^{2Patrocínio, M.C.A; ²Frota, P.T.T; ¹Vasconcelos, S.M.M.; ¹Carvalho, D.M.F.; ¹Carvalho, I.F.; ¹}Carvalho, M.D.F.; ²Magalhães P.J.C. and ¹Carvalho, K.M.

1 Lab. de Toxinologia, Instituto Superior de Ciências Biomédicas, UECE, Fortaleza, CE; 2 Departamento de Fisiologia e Farmacologia, UFC, Fortaleza, CE.

Bufadienolides are substances synthesized from cholesterol by some vertebrates, such as amphibians. Most of these compounds have demonstrated biological effects as vasoconstriction and the ability to inhibit Na⁺-K⁺-ATPase. Since preliminary data showed that telocinobufagin (TCB) has anesthetic effects, we evaluated its effects on the conduction of the compound action potential (CAP) in isolated rat sciatic nerve measured by extracellular recording technique. TCB was obtained by HPLC fractionation of the B. paracnemis parotoid glands venom. Isolated rat sciatic nerves were bathed in Locke solution at room temperature. In each nerve, action potentials were recorded before exposure to TCB solution, which served as the control data. The extracellular action potentials were recorded using a Dataq/CWE acquisition system (BMA-931, USA). The nerves were washed for 2 h with Locke’s solution and action potentials were recorded for impulse recovery. The experiments showed statistical difference compared to control (p<0.05, Dunnett’s test). In the presence of TCB the extracellular action potential peak-a-peak amplitude was decreased to 64.9±7.2% and 12.9±4.4% (n=7) relative to the control amplitude (3.4 ± 0.18 mV) after 15 and 30 min of toxin exposure, respectively. The PAC amplitude was recovered to 25.8±14.0 % after 15 min of wash, and reached 83.2± 17.5 % after 45 min. Bupivacaine was used as positive control, and at the same conditions, it reduced the PAC amplitude to 46.7± 14.4 % and 11.8± 6.5 % (n=5) of the control amplitude at 15 and 30 min, respectively. This study showed that exposing nerve to TCB cause reversible impulse blockade without neurotoxic effects.