Nonadrenergic, noncholinergic relaxation of human isolated corpus cavernosum induced by scorpion venom.
OBJECTIVE
To examine the effects of Tityus serrulatus scorpion venom (TSV) on human corpus cavernosum (HCC) using a bioassay cascade. Priapism is occasionally observed in scorpion envenomation, mostly in children.


METHODS
HCC strips were suspended in a cascade system and superfused with aerated and warmed Krebs' solution at 5 mL/min. Noradrenaline (3 micromol/L) was infused to induce a submaximal contraction of the HCC strips. The release of cyclooxygenase products was prevented by infusing indomethacin (6 micromol/L).


RESULTS
N(omega)-nitro-L-arginine methyl ester (10 micromol/L; n = 10) increased the tone of the preparations and significantly reduced (P <0.01) the acetylcholine (ACh) and TSV-induced relaxations. Subsequent infusion of L-arginine (300 micromol/L) partially reversed the increased tone and significantly restored the relaxations induced by TSV and ACh (P <0.01). The soluble guanylyl cyclase inhibitor ODQ (10 micromol/L; n = 8) markedly reduced (P <0.01) the relaxations induced by TSV, ACh, glyceryl trinitrate, and bradykinin. 7-Nitroindazole (10 micromol/L; n = 8) inhibited the relaxations induced by TSV by 84% (P <0.01) and also caused small, but significant, reductions in the ACh and bradykinin-induced HCC relaxations (P <0.05). Atropine (1 micromol/L; n = 6) abolished the relaxations evoked by ACh (P <0.01), but had no effect on those elicited by TSV. Tetrodotoxin (1 micromol/L; n = 6) abolished the relaxations induced by TSV (P <0.01) and also reversed the established TSV-induced relaxation (n = 4).


CONCLUSIONS
Our results indicate that TSV relaxes HCC through the release of nitric oxide from nonadrenergic, noncholinergic (NANC) nerves. The elucidation of the mechanism responsible for the TSV-induced relaxations might be useful for a better understanding of the development of priapism in cases of scorpion envenomation.
Teixeira
C E
CE
Department of Pharmacology, Faculty of Medical Sciences, Campinas, São Paulo, Brazil.
Faro
R
R
Moreno
R A
RA
Rodrigues Netto
N
N
Fregonesi
A
A
Antunes
E
E
De Nucci
G
G
D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D001120:Arginine / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010410:Penile Erection / Q000187:drug effects* / Q000502:physiology*; D010413:Penis / Q000294:innervation / Q000502:physiology*; D011317:Priapism / Q000139:chemically induced / Q000503:physiopathology; D012604:Scorpion Venoms; D013779:Tetrodotoxin / Q000494:pharmacology
D016861:Cyclooxygenase Inhibitors; D012604:Scorpion Venoms; D009569:Nitric Oxide; D013779:Tetrodotoxin; D001285:Atropine; D006632:Histamine; D001120:Arginine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine; D007213:Indomethacin