Voltage-dependent potassium currents of sympathetic preganglionic neurons in neonatal rat spinal cord thin slices.
Voltage-dependent potassium currents were analyzed in the visually identified sympathetic preganglionic neurons (SPNs) of neonatal rat spinal cord thin slices by the whole-cell patch-clamp technique. Some of the SPNs were identified by the presence of retrogradely transported fluorescent dye, DiI, injected into the superior cervical ganglion several days prior to experimentation. In a tetrodotoxin (TTX)-containing solution, a step depolarization from the holding potential of -72 mV generated a slow outward current that was suppressed by tetraethylammonium (TEA) and by Ca(2+)-free/2.5 ImM Co2+ solution. Ca(2+)-dependent current consisted of a transient and a sustained components. In a Ca(2+)-free (substituted with Mg2+) solution with TTX and TEA, a step depolarization from a hyperpolarized potential evoked a transient outward current that was blocked by 4-aminopyridine (4-AP). A step hyperpolarization evoked a voltage-dependent inward current, the conductance of which was dependent not only on the membrane potential, but also on the extracellular K+ concentration. Tail current analyses revealed that all of these currents were carried by K+ ions. These results indicate that SPN possesses at least five types of voltage-dependent K+ current, including the delayed rectifier current (IK), Ca(2+)-dependent transient current (IC), Ca(2+)-dependent sustained current (IAHP), A-current (IA) and inward rectifying current (Iu), which may be targets of putative transmitters released from various descending and segmental inputs impinging upon the SPN.
Miyazaki
T
T
Department of Physiology, Tokyo Medical College, Japan.
Dun
N J
NJ
Kobayashi
H
H
Tosaka
T
T
D000818:Animals; D000831:Animals, Newborn; D001339:Autonomic Fibers, Preganglionic / Q000166:cytology / Q000502:physiology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*
D015221:Potassium Channels