HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fisher, T. E. Articles by Bourque, C. W. Search for Related Content PubMed PubMed Citation Articles by Fisher, T. E. Articles by Bourque, C. W.

Density of transient K⁺ current influences excitability in acutely isolated vasopressin and oxytocin neurones of rat hypothalamus

Thomas E. Fisher, Daniel L. Voisin and Charles W. Bourque

1. The transient outward K⁺ current (I_TO) was studied using whole-cell recording in immunocytochemically identified oxytocin (OT; n = 23) and vasopressin (VP; n = 67) magnocellular neurosecretory cells (MNCs) acutely isolated from the supraoptic nucleus of adult rats.

2. The peak density of I_TO during steps to -10 mV was 26 % smaller in OT-MNCs (355 ± 23 pA pF^-1; mean ± s.e.m.; n = 18) than in VP-MNCs (478 ± 17 pA pF^-1; n = 52). No differences were observed in the voltage dependence of activation or inactivation.

3. Kinetic analysis revealed two components of I_TO inactivation in both OT-MNCs (₁ = 9·2 ± 0·4 ms and ₂ = 41·2 ± 1·6 ms; n = 18) and VP-MNCs (₁ = 12·4 ± 0·4 ms and ₂ = 37·1 ± 1·2 ms; n = 52). Although the density of the rapid component (₁) was not different (275 ± 13 versus 265 ± 16 pA pF^-1, respectively), the slow component (₂) was markedly smaller in OT-MNCs (183 ± 19 versus 331 ± 16 pA pF^-1 in VP-MNCs).

4. In unidentified MNCs, 0·5 mM 4-aminopyridine reduced I_TO amplitude by 29 % and decreased the latency to spike discharge by about 70 % during depolarization from -70 mV. Latency to discharge from potentials less negative than -60 mV, where I_TO is inactivated, was unaffected.

5. Comparison of latency to spike discharge in identified cells showed that OT-MNCs achieve spike threshold twice as fast as VP-MNCs when depolarized from -70 mV. The lower density of I_TO in OT-MNCs, therefore, accelerates the rate at which excitation can occur in response to depolarizing stimuli and may facilitate the occurrence of higher frequency discharges in OT-MNCs during physiological activation.

This article has been cited by other articles:

				K. J. Iremonger and J. S. Bains Integration of Asynchronously Released Quanta Prolongs the Postsynaptic Spike Window J. Neurosci., June 20, 2007; 27(25): 6684 - 6691. [Abstract] [Full Text] [PDF]

				W. Zhang, B. Star, W. R. A. K. J. S. Rajapaksha, and T. E. Fisher Dehydration increases L-type Ca2+ current in rat supraoptic neurons J. Physiol., April 1, 2007; 580(1): 181 - 193. [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]

				Y. Chakfe, Z. Zhang, and C. W. Bourque IL-1beta directly excites isolated rat supraoptic neurons via upregulation of the osmosensory cation current Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2006; 290(5): R1183 - R1190. [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]

				A. V. Ferguson, D. L.S. Washburn, and K. J. Latchford Hormonal and Neurotransmitter Roles for Angiotensin in the Regulation of Central Autonomic Function Experimental Biology and Medicine, February 1, 2001; 226(2): 85 - 96. [Abstract] [Full Text]

				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]

				R. Shibata, K. Nakahira, K. Shibasaki, Y. Wakazono, K. Imoto, and K. Ikenaka A-Type K+ Current Mediated by the Kv4 Channel Regulates the Generation of Action Potential in Developing Cerebellar Granule Cells J. Neurosci., June 1, 2000; 20(11): 4145 - 4155. [Abstract] [Full Text] [PDF]

				M.L.H.J. Hermes, J. M. Ruijter, A. Klop, R. M. Buijs, and L. P. Renaud Vasopressin Increases GABAergic Inhibition of Rat Hypothalamic Paraventricular Nucleus Neurons In Vitro J Neurophysiol, February 1, 2000; 83(2): 705 - 711. [Abstract] [Full Text] [PDF]