Effects of lanthanides on voltage-dependent potassium currents in bullfrog sympathetic neurons.
The effects of lanthanides (La(3+), Gd(3+), Lu(3+) and Sm(3+)) on voltage-dependent potassium currents were studied in dissociated bullfrog sympathetic neurons. A-type current (I(A)) and M-type current (I(M)) were blocked by lanthanides (0.1-30 microM) with I(M) being much less sensitive to these ions than I(A). The order of potency was Gd(3+)>/=Lu(3+) approximately La(3+) approximately Sm(3+) for I(A) and Gd(3+)&z.Gt;Lu(3+) approximately La(3+)>Sm(3+) for I(M). The I(M) block occurred independently of its activation kinetics while the I(A) block was associated with a positive shift of the activation and inactivation curves. Gd(3+) (100 microM) blocked the delayed rectifier-type current (I(K)) by less than 20%; Lu(3+), La(3+) and Sm(3+) (100 microM for each) were without effect on I(K). It is concluded that I(A) was the most sensitive to lanthanides, and Gd(3+) was the most potent for all the currents in amphibian autonomic neurons.
Department of Physiology, Tokai University School of Medicine, Bohseidai, 259-1193, Isehara, Japan.
T
T
Hirasawa
S
S
Kotani
T
T
Suzuki
K
K
Sato
M
M
Sakakibara
T
T
Tokimasa
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004594:Electrophysiology; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008674:Metals, Rare Earth / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D011892:Rana catesbeiana
D008674:Metals, Rare Earth; D015221:Potassium Channels