Amitriptyline modulation of Na(+) channels in rat dorsal root ganglion neurons.
The effects of amitriptyline, a tricyclic antidepressant, on tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neurons were studied using the whole-cell patch clamp method. Amitriptyline blocked both types of Na(+)currents in a dose-and holding potential-dependent manner. At the holding potential of -80 mV, the apparent dissociation constants (K(d)) for amitriptyline to block tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) channels were 4.7 and 105 microM, respectively. These values increased to 181 and 193 microM, respectively, when the membrane was held at a potential negative enough to remove the steady-state inactivation. Amitriptyline dose-dependently shifted the steady-state inactivation curves in the hyperpolarizing direction and increased the values of the slope factors for both types of Na(+) channels. The voltage dependence of the activation of both types of Na(+) channels was shifted in the depolarizing direction. It was concluded that amitriptyline blocked the two types of Na(+) channels in rat sensory neurons by modulating the activation and the inactivation kinetics.
Song
J H
JH
Department of Pharmacology, College of Medicine, Chung-Ang University, 221 Heuk-Suk Dong, Dong-Jak Ku, 156-756, Seoul, South Korea. jinhos@dragonar.nm.cau.ac.kr
Ham
S S
SS
Shin
Y K
YK
Lee
C S
CS
D000639:Amitriptyline / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D000639:Amitriptyline; D013779:Tetrodotoxin