| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Pharmacology, School of Pharmacy, University of London.
1. Magnocellular neurosecretory neurones were impaled in the supraoptic nucleus of perfused explants of rat hypothalamus. Membrane currents were studied at 35 degrees C using the single-microelectrode voltage-clamp technique. 2. Depolarizing voltage steps applied from -100 mV evoked a transient outward current (TOC) from a threshold of -75 mV. From this potential, the amplitude of the current increased non-linearly with voltage. 3. Following its activation TOC reached a peak within 7 ms and subsequently decayed monotonically with a time constant of 30 ms. This time constant did not vary significantly with voltage between -75 and -55 mV. 4. The TOC showed complete steady-state inactivation at potentials positive to -55 mV. Inactivation was removed by hyperpolarization, with a mid-point near -80 mV. The removal of inactivation followed a complex time course with distinct fast (tens of milliseconds) and slow (hundreds of milliseconds) components. 5. Tail current measurements revealed that the TOC equilibrium potential (ETOC) lies near -97 mV in the presence of 3 mM [K+]o. Increasing [K+]o caused a decrease of TOC amplitude and a shift in ETOC of 57 mV/log [K+]o. The TOC is therefore predominantly a K+ current. 6. The TOC was unaffected by tetraethylammonium (up to 12 mM) but was reversibly reduced by 4-aminopyridine (ca. 50% block at 1.0 mM) and dendrotoxin (ca. 50% block at 4 nM). 7. The TOC was strongly inhibited (greater than 70%) by adding Co2+ or Mn2+ (1-3 mM) or Cd2+ (50-400 microM) to Ca-containing solutions, or by removal of Ca2+ from the perfusate. These effects were not accompanied by detectable changes in threshold voltage. The amplitude of TOC was also depressed by the organic Ca2+ channel blocker methoxyverapamil (D600). Finally replacement of Ca2+ by Ba2+ in the perfusate completely and reversibly abolished the TOC. 8. These findings suggest that neurosecretory neurones of the rat supraoptic nucleus display a transient K+ current which is strongly dependent on the presence of external Ca2+. The possible role of this current is briefly discussed.
This article has been cited by other articles:
|
|
 |
|
  P. M. Sonner and J. E. Stern Functional role of A-type potassium currents in rat presympathetic PVN neurones J. Physiol., August 1, 2007; 582(3): 1219 - 1238. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. J. E. Stachniak and C. W. Bourque Visually guided whole cell patch clamp of mouse supraoptic nucleus neurons in cultured and acute conditions Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2006; 291(1): R68 - R76. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Teruyama and W. E Armstrong Enhancement of calcium-dependent afterpotentials in oxytocin neurons of the rat supraoptic nucleus during lactation J. Physiol., July 15, 2005; 566(2): 505 - 518. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Shevchenko, R. Teruyama, and W. E. Armstrong High-Threshold, Kv3-Like Potassium Currents in Magnocellular Neurosecretory Neurons and Their Role in Spike Repolarization J Neurophysiol, November 1, 2004; 92(5): 3043 - 3055. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. G. Birnbaum, A. W. Varga, L.-L. Yuan, A. E. Anderson, J. D. Sweatt, and L. A. Schrader Structure and Function of Kv4-Family Transient Potassium Channels Physiol Rev, July 1, 2004; 84(3): 803 - 833. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. A. Schrader, A. E. Anderson, A. Mayne, P. J. Pfaffinger, and J. D. Sweatt PKA Modulation of Kv4.2-Encoded A-Type Potassium Channels Requires Formation of a Supramolecular Complex J. Neurosci., December 1, 2002; 22(23): 10123 - 10133. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Luther, K. Cs. Halmos, and J. G. Tasker A Slow Transient Potassium Current Expressed in a Subset of Neurosecretory Neurons of the Hypothalamic Paraventricular Nucleus J Neurophysiol, October 1, 2000; 84(4): 1814 - 1825. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Fancsik, D. M. Linn, and J. G. Tasker Neurosteroid Modulation of GABA IPSCs Is Phosphorylation Dependent J. Neurosci., May 1, 2000; 20(9): 3067 - 3075. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Stern, M. Galarreta, R. C. Foehring, S. Hestrin, and W. E. Armstrong Differences in the Properties of Ionotropic Glutamate Synaptic Currents in Oxytocin and Vasopressin Neuroendocrine Neurons J. Neurosci., May 1, 1999; 19(9): 3367 - 3375. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G.-Y. Wang, D. W. Robinson, and L. M. Chalupa Calcium-Activated Potassium Conductances in Retinal Ganglion Cells of the Ferret J Neurophysiol, January 1, 1998; 79(1): 151 - 158. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. A. Schrader and J. G. Tasker Modulation of Multiple Potassium Currents by Metabotropic Glutamate Receptors in Neurons of the Hypothalamic Supraoptic Nucleus J Neurophysiol, December 1, 1997; 78(6): 3428 - 3437. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. E. Armstrong and J. E. Stern Electrophysiological and Morphological Characteristics of Neurons in Perinuclear Zone of Supraoptic Nucleus J Neurophysiol, November 1, 1997; 78(5): 2427 - 2437. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Papas and C. W. Bourque Galanin Inhibits Continuous and Phasic Firing in Rat Hypothalamic Magnocellular Neurosecretory Cells J. Neurosci., August 15, 1997; 17(16): 6048 - 6056. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. A. Schrader and J. G. Tasker Presynaptic Modulation by Metabotropic Glutamate Receptors of Excitatory and Inhibitory Synaptic Inputs to Hypothalamic Magnocellular Neurons J Neurophysiol, February 1, 1997; 77(2): 527 - 527. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Boudaba, K. Szabo, and J. G. Tasker Physiological Mapping of Local Inhibitory Inputs to the Hypothalamic Paraventricular Nucleus J. Neurosci., November 15, 1996; 16(22): 7151 - 7160. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Stern and W. E. Armstrong Changes in the Electrical Properties of Supraoptic Nucleus Oxytocin and Vasopressin Neurons during Lactation J. Neurosci., August 15, 1996; 16(16): 4861 - 4871. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
