THE EFFECT OF TX2-6 TOXIN OF Phoneutria nigriventer SPIDER IN ERECTILE FUNCTION IN RATS

NUNES K.P. (1), COSTA-GONÇALVES A. C. (1), LANZA L. F. (1), CORTES S. F. (1), CORDEIRO M. N. (4), RICHARDSON M. (4), PIMENTA A. M.C. (3), LEITE  R. (2), DE LIMA M.E. (3)

(1) Department of Physiology and Pharmacology, UFMG; (2) Department of Physiology, Medical College of Georgia, U.S.A; (3) Department of Biochemistry and Immunology, UFMG, Brazil. (4) FUNED, Foundation Ezequiel Dias, MG, Brazil.   

Severe human accidents involving the venom of spider Phoneutria nigriventer are characterized by different symptoms including priapism. The aim of this study is to investigate the role of the toxin Tx2-6, a peptide extracted from the venom of P. nigriventer, in the penile erection caused by the spider poisoning. Erectile function was measured in urethane anesthetized Wistar rats (230-250g) by continuous monitoring mean arterial pressure (MAP) and intracavernosal pressure (ICP) during electrical stimulation of the major pelvic ganglion. Voltage-response curves (0.5-3.0V, 12Hz, 0.1ms, 30s each step) were performed before and (15 min) after subcutaneous injection of Tx2-6 (12 g/Kg). The erectile response induced by ganglionic stimulation was significantly potentiated after injection of Tx2-6. Treatment with L-NAME (200 mg/Kg, i.c.), a non selective NOS (nitric oxide synthase) inhibitor, significantly impaired the erection, and this effect was not overcome by the treatment with Tx2-6. Incubation with Tx2-6 (0,1 and 0,01g/mL) caused a significant release of NO from rat isolated strips of corpus cavernosum, detected through a NO indicator (DAF-FM) using confocal microscopy. This study indicates that Tx2-6 is probably the component of the venom responsible for the priapism observed in poisoning accidents with the P. nigriventer spider, and that Tx2-6 induces and or potentiates penile erection by facilitating the nitric oxide -cyclic GMP pathway.

KEY WORDS: Phoneutria nigriventer, Tx2-6 toxin, nitric oxide, erectile dysfunction  

FINANCIAL SUPPORT: CNPq

CORRESPONDENCE TO: DE LIMA MARIA ELENA, Laboratory of Poison and Animals Toxins, LVTA, Belo Horizonte, Brazil. Phone: +55+31+3499 26 59. Fax: +55+31+3499 26 74. Email: delima@icb.ufmg.br