Persistent inward currents in cultured Retzius cells of the medicinal leech |
| |
Authors: | J D Angstadt |
| |
Institution: | (1) Department of Biology, Siena College, Loudonville, NY 12211, USA e-mail: Angstadt@Siena.edu Tel.: +1-518-783-4245; Fax: +1-518-783-2986, US |
| |
Abstract: | Current-clamp studies of cultured leech Retzius cells revealed inward rectification in the form of slow voltage sags in response
to membrane hyperpolarization. Sag responses were eliminated in Na+-free saline and blocked by Cs+, but not Ba2+. Voltage clamp experiments revealed a Cs+-sensitive inward current activated by hyperpolarization negative to −70 mV. Cs+ decreased the frequency of spontaneous impulses in Retzius cells of intact ganglia. Plateau potentials were evoked in Retzius
cells following block of Ca2+ influx with Ni2+ and suppression of K+ currents with internal tetraethylammonium. Plateau potentials continued to be expressed with Li+ as the charge carrier, but were eliminated when Na+ was replaced with N-methyl-d-glucamine. A persistent Na+ current with similar pharmacology that activated positive to −40 mV and reached its peak amplitude near −5 mV was identified
in voltage-clamp experiments. Inactivation of the persistent Na+ current was slow and incomplete. The current was revealed by slow voltage ramps and persisted for the duration of 5-s voltage
steps. Persistent Na+ current may underlie Na+-dependent bursting recorded in neurons of intact ganglia exposed to Ca2+-channel blockers.
Accepted: 22 September 1998 |
| |
Keywords: | Hyperpolarization-activated cation current Persistent sodium current Inward rectification Plateau potentials |
本文献已被 SpringerLink 等数据库收录! |
|