Characterization of a delayed rectifier potassium channel in the slowly adapting stretch receptor neuron of crayfish.
Single channel recordings were performed on enzyme-cleaned slowly adapting sensory neurons of crayfish, in cell-attached configuration, with a physiological K(+) gradient across the neuronal membrane. An outward rectifying, voltage-gated K(+) channel with a slope conductance of 13 pS and a K(+) ion permeability of P(K)=6.5 x 10(-14) cm(3)/s was characterized. This 13 pS K(+) channel started to be activated at around 20 mV depolarization. Its open probability increased upon depolarization with V(0.5)= -25.3 mV and P(max)=0.83. The averaged currents showed a delay following the onset of depolarization. The activation time constant was voltage-dependent. The maximal value was 17.0 ms at -25 mV and at +35 mV the time constant was 1.7 ms. Little inactivation was observed throughout the 80- or 1500-ms long depolarization pulses. A sum of two exponentials provided the optimal fit for open time and closed time distribution. At 80-mV depolarization, the open time constants were 0.4 and 10.4 ms; the close time constants were 0.4 and 2.3 ms. The first-latency distribution suggested that at least two closed states preceded two open states. This 13 pS delayed rectifier plays a minor role in the maintenance of the resting membrane potential but contributes to the action potential repolarization. It may also modify the stretch-induced receptor potential and affect the adaptation behaviours in this neuron.
Lin
J H
JH
Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77, Stockholm, Sweden.
Rydqvist
B
B
D000200:Action Potentials / Q000502:physiology*; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D003400:Astacoidea / Q000166:cytology / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology; D007700:Kinetics; D008465:Mechanoreceptors / Q000166:cytology / Q000378:metabolism*; D008959:Models, Neurological; D009420:Nervous System / Q000166:cytology / Q000378:metabolism*; D009431:Neural Conduction / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors
D015221:Potassium Channels