Activity dependence and functional role of the apamin‐sensitive K+ current in rat supraoptic neurones in vitro.

Kirkpatrick, Karen A.; Bourque, Charles W.

doi:10.1113/jphysiol.1996.sp021500

Cited by 86 publications

(108 citation statements)

References 32 publications

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“…1, the model contains several voltage-gated currents: the transient voltage-gated sodium current (I Na ) (Tanaka et al 1999), the delayed rectifier potassium current (I K(DR) ) , the A-type transient potassium current (I A ) , and L-and Ntype Ca 2+ currents (I Ca,L , I Ca,N ) (Foehring and Armstrong 1996;Joux et al 2001). It also contains the following Ca 2+ -dependent currents: a K + current mediated by large conductance K + (BK) channels (Dopico et al 1999), a K + current mediated by small conductance K + (SK) channels (Kirkpatrick and Bourque 1996), a non-selective cation (CAN) current (I CAN ) (Ghamari-Langroudi and Bourque 2002), and a slowly activated K + current in OT neurons Armstrong 1995,1997).…”

Section: 12mentioning

confidence: 99%

“…Activation of the SK channels is voltage independent and highly sensitive to intracellular Ca 2+ (Hille 2001;Sah and Davies 2000); BK channel activation is both voltage-and Ca 2+ -dependent (Vergara et al 1998;Dopico et al 1999). While activation of BK channels contributes to the falling phase of individual action potentials and the generation of the fast after hyperpolarizing potential (AHP) or hyperpolarizing after potential in many types of neurons (Lancaster and Adams 1986;Lancaster and Nicoll 1987;MacDermott and Weight 1982;Womack and Khodakhah 2002), including MNCs (Dopico et al 1999), SK channel activation is responsible for the generation of the AHP following a train of action potentials (Armstrong et al 1994;Bourque and Brown 1987;Greffrath et al 1998;Kirkpatrick and Bourque 1996;Lancaster and Adams 1986;Lancaster and Nicoll 1987;Sah and Bekkers 1996). This apamin-sensitive AHP is intermediate between the fast AHP (~50 ms) and "slow" AHP (lasting >5 s) (GhamariLangroudi and Bourque 2004).…”

Section: (A)mentioning

confidence: 99%

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Somato-dendritic mechanisms underlying the electrophysiological properties of hypothalamic magnocellular neuroendocrine cells: A multicompartmental model study

2007

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Magnocellular neuroendocrine cells (MNCs) of the hypothalamus synthesize the neurohormones vasopressin and oxytocin, which are released into the blood and exert a wide spectrum of actions, including the regulation of cardiovascular and reproductive functions. Vasopressin-and oxytocinsecreting neurons have similar morphological structure and electrophysiological characteristics. A realistic multicompartmental model of a MNC with a bipolar branching structure was developed and calibrated based on morphological and in vitro electrophysiological data in order to explore the roles of ion currents and intracellular calcium dynamics in the intrinsic electrical MNC properties. The model was used to determine the likely distributions of ion conductances in morphologically distinct parts of the MNCs: soma, primary dendrites and secondary dendrites. While reproducing the general electrophysiological features of MNCs, the model demonstrates that the differential spatial distributions of ion channels influence the functional expression of MNC properties, and reveals the potential importance of dendritic conductances in these properties.

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Section: 12mentioning

confidence: 99%

Section: (A)mentioning

confidence: 99%

Somato-dendritic mechanisms underlying the electrophysiological properties of hypothalamic magnocellular neuroendocrine cells: A multicompartmental model study

2007

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“…Spike frequency adaptation during a burst can be abolished by application of 50 -300 nM apamin (Bourque and Brown, 1987;Kirkpatrick and Bourque, 1996). This toxin is a specific blocker of SK channels, derived from bee venom, and so adaptation is caused by the progressive activation of an SK-like afterhyperpolarization (AHP) current (I AHP ) (Andrew and Dudek, 1984b;Bourque and Brown, 1987).…”

Section: Burst Structurementioning

confidence: 99%

Burst Initiation and Termination in Phasic Vasopressin Cells of the Rat Supraoptic Nucleus: A Combined Mathematical, Electrical, and Calcium Fluorescence Study

Roper¹,

Callaway²,

Armstrong³

2004

J. Neurosci.

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Vasopressin secreting neurons of the rat hypothalamus discharge lengthy, repeating bursts of action potentials in response to physiological stress. Although many electrical currents and calcium-dependent processes have been isolated and analyzed in these cells, their interactions are less well fathomed. In particular, the mechanism of how each burst is triggered, sustained, and terminated is poorly understood. We present a mathematical model for the bursting mechanism, and we support our model with new simultaneous electrical recording and calcium imaging data. We show that bursts can be initiated by spike-dependent calcium influx, and we propose that the resulting elevation of bulk calcium inhibits a persistent potassium current. This inhibition depolarizes the cell above threshold and so triggers regenerative spiking and further calcium influx. We present imaging data to show that bulk calcium reaches a plateau within the first few seconds of the burst, and our model indicates that this plateau occurs when calcium influx is balanced by efflux and uptake into stores. We conjecture that the burst is terminated by a slow, progressive desensitization to calcium of the potassium leak current. Finally, we propose that the opioid dynorphin, which is known to be secreted from the somatodendritic region and has been shown previously to regulate burst length and phasic activity in these cells, is the autocrine messenger for this desensitization.

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“…While such findings imply that receptors for glutamate must be expressed in the soma-dendritic membrane of MNCs, these cells are also known to be morphologically and physiologically resistant to the neurodegenerative effects of glutamatergic excitotoxins (e.g. (Hu & Bourque, 1991;Richard & Bourque, 1992;Kirkpatrick & Bourque, 1994).…”

Section: MD Brown School Of Sport and Exercise Sciences University Omentioning

confidence: 99%

“…More direct evidence has been obtained in hypothalamic explants where sustained activation of NMDA receptors has been shown to provoke the appearance of a clustered spiking activity resembling that observed upon dehydration in vivo . The occurrence of clustered firing in vitro has been shown to result from an interplay between the voltage-dependent properties of NMDA channels and the activity-dependent modulation of an apamin-sensitive, Ca2+-dependent K+ conductance Kirkpatrick & Bourque, 1994).…”

Section: MD Brown School Of Sport and Exercise Sciences University Omentioning

confidence: 99%

Symposium Proceedings

1995

The Journal of Physiology

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Starting with the earliest in vivo studies of the microcirculation, observers have been impressed with the variability and heterogeneity of microcirculation blood flow. The question I should like to address is how heterogeneity of microvascular perfusion influences transport of diffusible solutes, and how control of heterogeneity may contribute to regulation of blood-tissue exchange. Available exchange vessel surface area and inter-exchange vessel distances are controlled at the arteriolar level by the number of vessels open to the supply of arterial blood. When metabolic requirements are low, only a fraction of the exchange vessels in a vascular network are perfused; as metabolic activity increases, more exchange vessels are recruited. However, the efficiency with which available exchange vessel surface is utilized for diffusion of a given solute depends on the distribution of individual blood flow/permeability surface area ratios (Q/PS) in the network. Maximum efficiency (full utilization of available PS) is achieved when Q/PS is uniform.In vivo observations of red blood cell velocities show wide variation among individual exchange vessels of the same class (capillaries, postcapillary venules); presumably the same is true of plasma velocities. Flow velocity is only one of the factors that determines local transport; the critical parameter is the product of velocity and vessel radius divided by vessel length times solute permeability (v. r/ 1 P). The impression I get from published intra-vital microscope data is that this ratio may vary even more widely than velocity alone. Physiological measurements of solute transport in whole organs provide indirect support for broad heterogeneity of perfusion, at least in low metabolic states. In resting skeletal muscles the apparent (measured) PS products for 86Rb and 51Cr EDTA increase with increasing perfusion rate, approaching limiting values at high flow rates, as predicted for a heterogeneity perfused assemblage of exchange vessels. Estimated coefficients of variation (cv = S.D./mean) of Q/PS or v. r/ 1 P lie in the range 07-09.In heterogeneously perfused organs and tissues, the degree of heterogeneity (cv of Q/PS) and the total blood flow are potentially important secondary regulators of capillary transport, because they determine the efficiency with which the primary controlling factors, total blood flow and available exchange vessel surface area, are utilized (note that blood flow acts both directly and indirectly). Efficiency, defined as the ratio of apparent PS to the maximum PS at uniform perfusion, is inversely related to the degree of heterogeneity and directly related to the mean flow velocity. There is conflicting evidence in the literature concerning the degree to which alteration of Q/PS heterogeneity is involved in adaptive control of diffusion exchange. However, even with constant total PS and fixed heterogeneity, an increase in total blood flow can decrease the influence of heterogeneity on transport and thus contribute substantially to Berlin 33, Ger...

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Activity dependence and functional role of the apamin‐sensitive K+ current in rat supraoptic neurones in vitro.

Cited by 86 publications

References 32 publications

Somato-dendritic mechanisms underlying the electrophysiological properties of hypothalamic magnocellular neuroendocrine cells: A multicompartmental model study

Somato-dendritic mechanisms underlying the electrophysiological properties of hypothalamic magnocellular neuroendocrine cells: A multicompartmental model study

Burst Initiation and Termination in Phasic Vasopressin Cells of the Rat Supraoptic Nucleus: A Combined Mathematical, Electrical, and Calcium Fluorescence Study

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