[
Worm Breeder's Gazette,
2001]
We regret to inform the C. elegans community that the published recipe for internal saline for whole-cell recordings[1,2] from neurons was incorrect. The published recipe was (in mM): KGluconate 125, KCl 18, NaCl 0, CaCl2 0.7, MgCl2 1, HEPES 10, EGTA 10. The recipe actually used was (in mM): KGluconate 125, KCl 18, NaCl 4, CaCl2 0.6, MgCl2 1, HEPES 10, EGTA 10. The main effect of this error resides in the difference in NaCl concentration. The correct saline will produce a predicted Na reversal potential of 90 mV with the published external saline, while the erroneous published saline has an undefined ENa. Because C. elegans lacks voltage-gated Na channels, this difference in salines may have little or no effect on recordings of voltage-gated currents. It may, however, affect measurements of currents carried by ligand-gated currents and currents carried by DEG/ENaC channels. We apologize for any inconvenience this error may have caused. 1. Goodman, M.B., Hall, D.H., Avery, L., and Lockery, S.R. (1998) Active Currents Regulate Sensitivity and Dynamic Range in C. elegans Neurons. Neuron 20:763-772. 2. Lockery, S.R. and Goodman, M.B. (1998) Tight-seal whole-cell patch clamping of C. elegans neurons. Methods in Enzymology 295:201-217.
[
Worm Breeder's Gazette,
1995]
Using simple modifications of existing techniques, I have recentlymade intracellular recordings from neurons and muscles in C. elegans. Larvae (approx. L2) were glued with cyanoacrylate adhesive to acoverslip coated with a moist agarose film.1 The coverslip formed thebottom of the recording chamber, which was filled with a physiologicalsaline and viewed on an inverted microscope using Nomarski optics. Animals were dissected in a two-step procedure. First, internal pressurewas relieved by nicking the cuticle in the mid-gut using a tungstenneedle. Second, either the pharynx or a small bouquet of neurons wasexposed by making a nick in the cuticle of the head. Intracellularmicroelectrodes were used to record from the pharynx and patch electrodeswere used to record from neurons. Microelectrode recordings from muscles of the spontaneously pumpingpharynx revealed rhythmic depolarizations with an amplitude of 50 to 70 mVand a duration of several hundred milliseconds. These events closelyresembled action potentials previously recorded from the pharynx ofAscaris,2 indicating that important aspects of physiological function areretained after gluing and dissection. As a first step in understanding the basic operating principles ofthe C. elegans nervous system, I have concentrated primarily on whole-cellvoltage-clamp recordings. Twenty-one whole-cell or perforated patchrecordings have been made so far. Neuronal input capacitance ranged from0.1 to 2.0 pF. The low end of this range is the capacitance expected ofan isolated L2 soma,3 while the upper end is the capacitance expected ofan L2 neuron with a process about 50 mm long. The apparent neuronal inputresistance ranged from 0.1 to 7.1 G ohms. Patch clamp methodssystematically underestimate capacitance and resistance in small neurons.Nevertheless, these data indicate the membrane time constant, whichdetermines how fast a neuron responds to its inputs, is at least 14 ms. They also suggest the axonal space constant, which determines how far aninput signal propagates passively, is at least 150 mm. This means thatinterneurons confined to the nerve ring should be effectivelyisopotential. Two classes of neurons could be distinguished by differences intheir voltage-dependent currents. Cells of the first class had sustainedoutward currents but no inward currents. Cells of the second class had atransient outward current and also a small, sustained inward current. Because the inward current activates more rapidly and at lower clampvoltages than the outward current, these cells may be capable ofregenerative potentials. Until now, all recordings have been from unidentified neurons. I amhopeful, however, that by using GFP4 labeled worms I will be able torecord from identified neurons. If so, it should be possible to determinewhether different types of neurons have different electrophysiologicalproperties and to correlate these differences with the behavioral rolespredicted by anatomical and laser ablation experiments. Moreover, bycrossing GFP animals with mutant strains, I hope to record from identifiedcells in mutants. Thus, it should be possible to combine theelectrophysiological and the genetic analysis of behavior at the cellularlevel in individual neurons.1. Avery, L., Raizen, D., and Lockery, S.R. (1995) Electrophysiological Methods. In Epstein, H.F. and Shakes, D.C. (eds.) C. Elegans: Modern Biological Analysis of an Organism. Academic Press, Orlando (in press).2. Byerly L., Masuda, M.O. (1979). J. Physiol. 288:263-284.3. David Hall, unpublished data.4. Chalfie, M., Tu, Y., Euskirchen, G., Ward, W.W. and Prasher, D.C. (1994). Science 263:802-5.