Combination electrodes in microiontophoresis
Microiontophoresis is most often used in conjunction with extracellular recording of neuronal firing. Extracellular 'spikes' are tipically few hundred microvolts in amplitude and are generated by action potentials across the membranes of neurons. They can be recorded through the center barrel of a multibarrel pipette if filled with a suitable electrolyte solution such as sodium chloride. However, electrolyte-filled glass micropipettes in a multibarrel assembly are electrically very noisy. The solid-conductor microelectrodes such as the tungsten or carbon fiber electrodes, in contrast, show significantly less noise in extracellular recordings. Because of this, many attempts have been made to combine a tungsten electrode with a set of iontophoresis barrels. The usual technique has been to glue the two types of electrodes together (piggyback configuration) or to insert a presharpened tungsten wire into one of the barrels (metal-in-glass configuration). Either method is technically very difficult and time consuming procedure. The coaxial, carbon fiber containing recording/microiontophoresis combination electrodes are considerably easier and cheaper to make than tungsten electrodes. Carbon fibers are 5-8 micrometer in diameter and they provide excellent signal-to-noise ratio recordings (see example below). Carbon fiber electrodes can also be used for voltammetric analysis of transmitters in vivo (Millar 1991). This page aims to introduce our CARBOSTAR series carbon fiber electrodes which are used for iontophoresis and extracellular recording/electrochemical analyses with great success.
Our Carbostar electrodes are made by a unique dry fabrication method so their shipping over great distances is safe. Iontophoresis barrels are self filling which make their usage easy with plug and play simplicity. For purchase, see Kation Scientific's Order and Price list page.
| Carbostar-1
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Scanning electron micrograph of the tip of a Carbostar-1
electrode (left). View of the same electrode (above). |
Single barrel carbon fiber electrodes
for extracellular recording and/or in vivo voltammetry.
Price information Related item:
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| Carbostar-3
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The three barrel Carbostar-3 carbon
fiber combination electrodes are for extracellular recording and microiontophoresis.
One barrel contains the carbon fiber as the recording element, the other
two barrels are for microiontophoresis. Recommended when only recording
site is to be marked with iontophoresed tracer material or when one
or two substances are to be tested on neuronal firing. Note the internal
glass filaments within the iontophoresis barrels (arrows) which allow
self filling of aqueous solutions. Price information Related items: ExAmp-20KB extracellular amplifier Union-40 nanoampere iontophoresis pump BAB-501 microampere iontophoresis pump |
| Carbostar-4
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The four barrel Carbostar-4 carbon
fiber combination electrodes are for extracellular recording and microiontophoresis.
Recommended when two or three substances are to be tested on neuronal
firing. Price information Related items: |
| Carbostar-6
|
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The six barrel Carbostar-6 carbon
fiber combination electrodes are for extracellular recording and microiontophoresis.
Recommended when up to five substances are to be tested on neuronal
firing. Price information Related items: |
Light microscopic image of the CARBOSTAR-7 electrode showing the carbon fiber tip protruding from the glass shank of 6 fused-together iontophoresis barrels. The correct tip length was reached by spark etching of the excessive length of carbon fiber according to the method of Williams et al. (1992). The stiffness of the carbon fiber provides good mechanical stability to the electrode and the sharp tip allows easy tissue penetration. Impedances at 1 kHz: Ultrastructure of the CARBOSTAR-7S electrode as revealed by scanning
electron microscopy. The fused-together glass micropipettes form a
seal around the protruding carbon fiber. Microiontophoresis can be
achieved through the microscopic orifices of the pipettes. Related items: |
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| Sample recording
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Recording was taken
from a brainstem neuron using an ExAmp-20KB in combination with a Carbostar-3
carbon fiber electrode. Cell firing was evoked by iontophoresed NMDA.
Currents for the NMDA iontophoresis were delivered by a Union-40
iontophoresis pump. The amplified signals were sampled and digitized
at 20 KHz frequency by a National
Instruments PCI-1200 data acquisition board. |
| Marking recording
site with Pontamine Sky Blue
|
Site of extracellular
recording from the hippocampus of the rat was marked by Pontamine Sky
Blue (PSB) ejection from an iontophoresis barrel of a Carbostar-4
electrodes. Four % (w/v) PSB solution was made in 0.1 M sodium-acetate solution and was filtered through a 0.1 mm syringe filter just before use. The filtered solution was filled in an iontophoresis barrel of a Carbostar-4 electrode using a PE-10 tubing after extracellular recording and was left equilibrate there for 15 minutes. Iontophoretic ejection was accomplished by a BAB-500 iontophoresis pump using -5 mA for 15 minutes. Tissue was sliced by a vibratome to 50 mm slices. Slices were then counterstained by simple neutral red procedure. |
To place an order see Kation Scientific's Order and Price list page.
| References: |
| Anderson, C.W. and M.R. Cushman (1981) A simple and rapid method for making carbon fiber microelectrodes. Journal of Neuroscience Methods, 4: p.435-435 |
| Armstrong-James, M. and J. Millar (1979) Carbon fibre microelectrodes. Journal of Neuroscience Methods, 1: 279-287. |
| Armstrong-James, M., K. Fox and J. Millar (1980) A method for etching the tips of carbon fibre microelectrodes. Journal of Neuroscience Methods, 2: p.431-432. |
| Armstrong-James, M., K. Fox, Z.L. Kruk and J. Millar (1981) Quantitative iontophoresis of cathecolamines using multibarrel carbon fiber microelectrodes. Journal of Neuroscience Methods, 4: p.385-406. |
| Armstrong-James, M., J. Millar and Z.L. Kruk (1980) Quantification of noradrenaline iontophoresis. Nature, 288: p.181-183. |
| Budai, D. and Zs. Molnár (2001) Novel carbon fiber microeletrodes for extracellular electrophysiology. Acta Biologica Szegediensis, 45:65-73. Full length article in PDF |
| Conn, P.M., ed. (1991) Electrophysiology and microinjection. Methods in Neurosciences, Vol. 4. Academic Press: San Diego. |
| Dreyer, F. and K. Peper (1974) Iontophoretic application of acetylcholine: advantages of high resistance micropipettes in connection with an electronic current pump. Pflügers Archive, 348: p. 263-272. |
| Fu, J. and J.F. Lorden (1996) An easily constructed carbon fiber recording and microiontophoresis assembly. Journal of Neuroscience Methods, 68: p. 247-251. |
| Gerhardt, G.A. and M.R. Palmer (1987) Characterization of the Techniques of Pressure Ejection and Microiontophoresis Using In-Vivo Electrochemistry. Journal of Neuroscience Methods, 22(2): p. 147-160. |
| Godwin, D.W. (1994) A tungsten-in-glass iontophoresis assembly for studying input-output relationships in central neurons. Journal of Neuroscience Methods, 49: p.211-223. |
| Gottschaldt, K.M., T.P. Hicks, and C. Vahle-Hinz (1988) A combined recording and microiontophoresis technique for input-output analysis of single neurons in the mammalian CNS. Journal of Neuroscience Methods, 23(3): p. 233-240. |
| Haidarliu, S., D. Shulz, and E. Ahissar (1995) A multi-electrode array for combined microiontophoresis and multiple single-unit recordings. Journal of Neuroscience Methods, 56(2): p. 125-131. |
| Hellier, M., P. Boers, and G.A. Lambert (1990) Fabrication of a metal-cored multi-barrelled microiontophoresis assembly. Journal of Neuroscience Methods, 32(1): p. 55-62. |
| Hicks, T.P. (1984) The history and development of microiontophoresis in experimental neurobiology. Progress in Neurobiology, 22: p. 185-240. |
| Li, B.M., Z.T. Mei and K. Kubota (1990) Multibarreled glass-coated tungsten microelectrode for both neuronal activity recording and iontophoresis in monkeys. Neuroscience Research, 8(3): p.214-219. |
| Maisky, V.A. and V.Y. Fridlyansky (1993) A method for bevelling of microelectrodes by means of vibration. Journal of Neuroscience Methods, 49(3): p. 241-244. |
| Merril, E.G. and A. Ainsworth (1972) Glass-coated platinum plated metal microelectrodes. Med. Biol. Eng., 10: p. 662-667. |
| Millar J. (1991)Simultaneous in vivo voltammetric and electrophysiological recording with carbon fiber microelectrodes. In: Electrophysiology and microinjection. Methods in Neurosciences, Vol. 4. (Conn, P.M., ed.) Academic Press: San Diego, p. 143-154. |
| Millar, J. and C.W.A. Pelling (2001) Improved methods for construction of carbon fibre electrodes for extracellular spike recording. Journal of Neuroscience Methods, 10: 1-8. |
| Millar, J. and Williams, G. V. (1988) Ultra-low noise silver-plated carbon fiber microelectrodes. Journal of Neuroscience Methods, 25: 59-62. |
| Purves, R.D. (1981) Microelectrode methods for intracellular recording and iontophoresis. New York: Academic Press. |
| Sawaguchi, T., M. Matsumura and K. Kubota (1986) Long-lasting marks of extracellularly recorded sites by carbon fiber glass micropipette in the frontal cortex of chronic monkeys. Journal of Neuroscience Methods, 15: p.341-348. |
| Shi, W.X. and B.S. Bunney (1990) A simple and effective method for preventing the formation of salt bridges between barrels of a multibarrel microiontophoresis electrode. Journal of Neuroscience Methods, 35(1): p. 89-91. |
| Stamford, J.A., ed. (1992) Monitoring neuronal activity: a practical approach. Oxford University Press: Oxford. |
| Verberne, A.J.M, N.C. Owens and G.P. Jackman (1995) A simple and reliable method for construction of parallel multibarreled microelectrodes. Brain Research Bulletin, 36: p.107-108. |
| Williams, G. V. and Millar, J. (1990) Differential actions of endogenous and iontophoretic dopamine in rat striatum. European Journal of Neuroscience, 2: p.658-661. |
| Williams, J.E.G., Millar J. and Kruk, Z.L. (1992) Preparation of Spark-Etched Nodes for Fast Cyclic Voltammetry. British Journal of Pharmacology, 107. |
| Williams, J.E.G., Millar J. and Kruk, Z.L. (1992) A Comparison of Cut and Spark-Etched Electrodes for Fast Cyclic Voltammetry. British Journal of Pharmacology, 107. |
| Yu, D. and F.J. Gordon (1994) A simple method to improve the reliability of iontophoretic administration of tracer substances. Journal of Neuroscience Methods, 52(2): p. 161-164. |