Whole-cell recording of the Ca2+-dependent slow afterhyperpolarization in hippocampal neurones: effects of internally applied anions

Abstract

Using the whole-cell recording technique, we have examined the slow Ca(2+)-activated afterhyperpolarization (AHP) and its underlying current (IAHP) in hippocampal CA1 neurones of brain slices obtained from mature rats. Specifically we have studied the effects of the anion component of various K+ salts commonly used to make the pipette filling solution that dialyses neurones during whole-cell recordings. Among the K+ salts examined which included potassium methylsulfate, potassium methanesulfonate, potassium gluconate, potassium chloride, potassium citrate and potassium glutamate, stable AHPs/IAHP and strong spike firing adaptation could only be observed in neurones recorded with the patch pipette solution containing potassium methylsulfate. These AHPs and firing patterns closely mimicked those recorded with sharp electrodes. Similarly, the sustained component of voltage-activated Ca2+ currents was more stable in neurones dialysed with cesium methanesulfonate than in those dialysed with cesium gluconate or cesium chloride. Although the mechanisms underlying the interaction(s) between internally applied anions and ionic channels need further investigation, the present experiments illustrate that in mammalian brain neurones at 33 degrees C, the Ca(2+)-activated IAHP is dramatically altered by internal anions. We suggest that among anions commonly used in electrode filling solutions for whole-cell recordings, methylsulfate is the least disruptive to intracellular structures or Ca2+ homeostasis and permits stable whole-cell recording of the IAHP and Ca2+ currents in mammalian CNS neurones.

Integration Time in a Subset of Spinal Lamina I Neurons Is Lengthened by Sodium and Calcium Currents Acting Synergistically to Prolong Subthreshold Depolarization

“…Pipettes were filled with an intracellular solution containing the following (in mM): 135 KMeSO 4 , 5 KCl, 10 HEPES, 2 MgCl 2 , 4 ATP (Sigma, St. Louis, MO), and 0.4 GTP (Sigma), pH was adjusted to 7.2 with KOH, and osmolarity ranged from 270 to 290 mOsm. Intracellular Ca 2ϩ was not buffered to avoid possible effects on firing pattern (Schwindt et al, 1992;Staley et al, 1992;Zhang et al, 1994). Although morphology data are not described here, ϳ0.1% Lucifer yellow (dipotassium salt; Sigma) was included in the recording solution to allow visualization of neuronal morphology after recording.…”

Chronic Intermittent Ethanol Exposure Enhances the Excitability and Synaptic Plasticity of Lateral Orbitofrontal Cortex Neurons and Induces a Tolerance to the Acute Inhibitory Actions of Ethanol

“…Chronic ethanol alters OFC excitability S Nimitvilai et al by the calcium chelator EGTA or gluconate (Velumian et al, 1997;Zhang et al, 1994). To determine whether this occurs in lOFC neurons, we compared the effects of different internal pipette solutions on SK currents in a small set of lOFC neurons from naive mice.…”

Diversity of Gain Modulation by Noise in Neocortical Neurons: Regulation by the Slow Afterhyperpolarization Conductance

“…We and Fellous et al (2003) used KMeSO 4 intracellular solutions, which maintain the sAHP better than solutions containing other anions (Zhang et al, 1994). Chance et al (2002) used K-gluconate, Rauch et al (2003) used K-gluconate and high EGTA, and Shu et al (2003) used sharp electrodes containing K-acetate.…”