Differences between pacemaker and nonpacemaker neurons of Aplysia on voltage clamping.
The responses of pacemaker and nonpacemaker Aplysia neurons to voltage clamp commands of less than 200 msec duration are essentially identical. For moderate depolarizing commands there is an early inward transient current followed by a late outward current and an outward tail current when the membrane is clamped back to resting potential. On long (1-2 sec) commands in pacemakers there is a marked sag in the late current and an inward tail current. E(tail), the potential of the membrane at which there is no net current flow under the conditions prevailing at the end of the clamp, shifts from about -9.0 mv on short commands to +5.0 mv on long commands. In contrast there is no marked sag of the late current or inward tail current on long commands in nonpacemakers, and E(tail) is near -9.0 mv for both short and long commands. The current sag and shift in E(tail) can be ascribed to a decreased conductance (presumably to K(+)) at the end of the long as compared to the short command in half of the pacemaker neurons. In the remaining cells the essential difference from nonpacemakers appears to be either a greater restricted extracellular space or a more active potential-dependent electrogenic Na(+) pump in pacemakers.
D000818:Animals; D004594:Electrophysiology; D005724:Ganglia / Q000502:physiology*; D008566:Membranes / Q000502:physiology; D008722:Methods; D008974:Mollusca; D009431:Neural Conduction; D009474:Neurons / Q000502:physiology*
J Gen Physiol. 1967 Jul;50(6):1469-84
6034753
J Gen Physiol. 1968 Jan;51(1):29-45
5642472
Science. 1968 Oct 25;162(3852):456-8
4234647
J Gen Physiol. 1968 Jul;52(1):1-21
5742832
J Physiol. 1957 Oct 30;138(3):341-64
13481878
Pflugers Arch. 1958;267(6):553-65
13613922
Biophys J. 1961 May;1:401-18
13694550
J Gen Physiol. 1962 Mar;45:821-36
14488667
J Gen Physiol. 1962 Jul;45:1077-97
13919850
J Gen Physiol. 1961 Nov;45:317-30
13922329
Z Zellforsch Mikrosk Anat. 1963;60:213-36
13990907
J Gen Physiol. 1965 Jan;48:489-514
14284780
J Physiol. 1956 Feb 28;131(2):341-76
13320339
J Physiol. 1959 Oct;148:161-79
14398823