How does tetrodotoxin affect sodium channels?
Tetrodotoxin (TTX) is a potent toxin that specifically binds to voltage gated sodium channels. TTX binding physically blocks the flow of sodium ions through the channel, thereby preventing action potential (AP) generation and propagation.
What channels does tetrodotoxin block sodium?
4. Tetrodotoxin (TTX) blocks sodium channels from outside the nerve membrane in the cationic form, whereas local anesthetic molecules penetrate the nerve membrane in the uncharged form (B) and block both sodium and potassium channels from inside the nerve membrane in the cationic form.
What is TTX sensitive?
TTX-resistant Na+ channels have been found in cell bodies of many peripheral nervous system (PNS) neurons in both immature and mature animals. However, TTX-resistant Na+ channels have been reported in only a few types of central nervous system (CNS). Axons of PNS and CNS neurons are sensitive to TTX.
Are muscle cells affected by tetrodotoxin?
On the ventricular muscle, tetrodotoxin blocked the spike generation triggered by electrical stimulation (0.4 c/sec 5 msec) without any change of the membrane potential. without change of the resting potential.
How does tetrodotoxin affect resting membrane potential?
Tetrodotoxin blocks the action potential and both the inward and outward transient current, but has no effect on either the resting membrane potential or the steady-state current.
What happens if sodium channels are blocked?
Complete block of sodium channels would be lethal. However, these drugs selectively block sodium channels in depolarized and/or rapidly firing cells, such as axons carrying high-intensity pain information and rapidly firing nerve and cardiac muscle cells that drive epileptic seizures or cardiac arrhythmias.
What are the symptoms of tetrodotoxin?
Some of the symptoms induced by the TTX are headache, diaphoresis, body numbness, dysarthria, dysphagia, nausea, vomiting, abdominal pain, generalized malaise, weakness, and lack of coordination and, in more severe cases, hypotension, cardiac arrhythmias, muscle paralysis, and cranial nerve dysfunction may develop.
How is the effects of lidocaine different from TTX?
Both drugs block voltage-dependent sodium channels. However, TTX and lidocaine differ in the duration of their effects, with maximum TTX effect between 30 min and 120 min, washing out in 24 hours. Lidocaine maximum effect occurs 20-30 minutes after administration.
How does lidocaine affect action potential?
At low (therapeutic) doses, lidocaine induced a small reduction in action potential duration and contraction but had no effect on transient depolarizations or, under voltage-clamp conditions, on the transient inward currents.
How does tetrodotoxin work in the body?
Human poisonings occur when the flesh and/or organs of the fish are improperly prepared and eaten. Tetrodotoxin interferes with the transmission of signals from nerves to muscles and causes an increasing paralysis of the muscles of the body. Tetrodotoxin poisoning can be fatal.
Does low dose of tetrodotoxin reduce neuropathic pain behavior?
Lyu Y.S., Park S.K., Chung K., Chung J.M. Low dose of tetrodotoxin reduces neuropathic pain behaviors in an animal model. Brain Res. 2000;871:98–103.
Which sodium channels are expressed along nonmyelinated axons in the brain?
Black J.A., Renganathan M., Waxman S.G. Sodium channel Nav1.6 is expressed along nonmyelinated axons and it contributes to conduction. Brain Res. Mol. Brain Res. 2002;105:19–28.
Can TTX block TTX-sensitive VGSCs in pathological pain?
This change in gene regulation leads to electrophysiological changes which may play a key role in the pathogenesis of the pain outcome. Therefore, the use of TTX seems reasonable as a possible pharmacological tool to block TTX-sensitive VGSCs in pathological pain conditions.
Which sodium channel accumulates at the site of infraorbital nerve injury?
Henry M.A., Freking A.R., Johnson L.R., Levinson S.R. Sodium channel Nav1.6 accumulates at the site of infraorbital nerve injury. BMC Neurosci. 2007;8doi: 10.1186/1471-2202-8-56.