TY - JOUR
T1 - Pharmacological characterization of the presynaptic activity of Tityus serrulatus venom in the rat anococcygeus muscle
AU - Teixeira, Cleber E.
AU - Priviero, Fernanda B.M.
AU - Okuyama, Cristina E.
AU - De Nucci, Gilberto
AU - Antunes, Edson
N1 - Funding Information:
The authors are grateful to Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for providing financial support.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2003/10
Y1 - 2003/10
N2 - Scorpion venoms are known to cause peripheral nerve stimulation with enhanced autonomic responses. This study, therefore, examined the effects of Tityus serrulatus venom (TSV) on adrenergic, cholinergic and nitrergic nerve fibers using the rat anococcygeus muscle. The contractile effects of TSV (1 μg/ml) and electrical field stimulation were markedly reduced by phentolamine (5 μM), prazosin (0.1 μM), guanethidine (30 μM) and tetrodotoxin (TTX, 1 μM), whereas imipramine (3 μM) enhanced these responses. The responses to tyramine (10 μM) were partially reduced by guanethidine and completely blocked by phentolamine, prazosin and imipramine. Atropine (1 μM) fully prevented carbachol (CCh, 30 μM)-induced contractions without affecting those mediated by TSV. Neostigmine significantly potentiated TSV-and ACh-evoked contractions, whereas hexamethonium had no effect. The relaxant responses induced by EFS and TSV (3 μg/ml) were completely blocked by L-NAME (100 μM), ODQ (1 μM) or TTX (1 μM). Addition of L-arginine (1 mM) reversed the effect of L-NAME. Thus, the motor and inhibitory responses of TSV in the rat anococcygeus muscle are mediated by prejunctional mechanisms dependent on Na+ channel activation, causing the stimulation of NA and NO release from adrenergic and nitrergic nerve fibers, respectively.
AB - Scorpion venoms are known to cause peripheral nerve stimulation with enhanced autonomic responses. This study, therefore, examined the effects of Tityus serrulatus venom (TSV) on adrenergic, cholinergic and nitrergic nerve fibers using the rat anococcygeus muscle. The contractile effects of TSV (1 μg/ml) and electrical field stimulation were markedly reduced by phentolamine (5 μM), prazosin (0.1 μM), guanethidine (30 μM) and tetrodotoxin (TTX, 1 μM), whereas imipramine (3 μM) enhanced these responses. The responses to tyramine (10 μM) were partially reduced by guanethidine and completely blocked by phentolamine, prazosin and imipramine. Atropine (1 μM) fully prevented carbachol (CCh, 30 μM)-induced contractions without affecting those mediated by TSV. Neostigmine significantly potentiated TSV-and ACh-evoked contractions, whereas hexamethonium had no effect. The relaxant responses induced by EFS and TSV (3 μg/ml) were completely blocked by L-NAME (100 μM), ODQ (1 μM) or TTX (1 μM). Addition of L-arginine (1 mM) reversed the effect of L-NAME. Thus, the motor and inhibitory responses of TSV in the rat anococcygeus muscle are mediated by prejunctional mechanisms dependent on Na+ channel activation, causing the stimulation of NA and NO release from adrenergic and nitrergic nerve fibers, respectively.
KW - ACh, acetylcholine
KW - Adrenergic transmission
KW - Anococcygeus muscle
KW - CCh, carbachol
KW - EFS, electrical field stimulation
KW - GTN, glyceryl trinitrate
KW - Na channels
KW - Nitrergic transmission
KW - Nitric oxide
KW - Noradrenaline
KW - Tityus serrulatus
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U2 - 10.1016/S0041-0101(03)00172-7
DO - 10.1016/S0041-0101(03)00172-7
M3 - Article
C2 - 14529726
AN - SCOPUS:1542601415
SN - 0041-0101
VL - 42
SP - 451
EP - 460
JO - Toxicon
JF - Toxicon
IS - 5
ER -