Chapter 13 Chapter Cytosolic free calcium in hippocampal CA3 pyramidal cells

The dynamics of cytosolic free Ca²⁺ ([Ca²⁺]_i) of single voltage-clamped CA3 pyramidal cells in hippocampal slice cultures is reviewed. [Ca²⁺]_i amounts to about 30 nM at resting membrane potential and increases slowly when the membrane potential is clamped at more positive values (up to 500 nM at -30 mV). Short lasting depolarizations (40–100 ms) induce a transient rise in [Ca²⁺]_i which activates a slow aftercurrent (I_AHP). The muscarinic or β-adrenergic depression of I_AHP is not accompanied by any change in the dynamics of Ca²⁺ and appears, therefore, to result primarily from an inhibition of the K⁺-current itself or of the ability of Ca²⁺ to activate the current. At higher concentrations than those required to inhibit I_AHP, muscarine produces a pronounced inward current and this is accompanied by a rise in resting [Ca²⁺]_i concentration.