Fig. 3. Simultaneous fluorometric and electrophysiologic recording in neurons of intact ganglia. Cytosolic Ca²⁺transients in the neuronal soma (left ) are generated by action potentials (APs) triggered by dorsal root stimulation (downward arrows ). Simultaneous recording of the membrane potential (right , correlating with numbered upward arrows  in left ) identifies the presence or absence of AP invasion into the soma. (A ) Withdrawal of bath Ca²⁺abolishes the Ca²⁺transient despite persistence of APs (trace 2). (B ) Bath-applied lidocaine (1 mm) blocks the transmission of APs (trace 2), which abolish the Ca²⁺transient; typical of n = 6. (C ) Only APs elicit a Ca²⁺transient (trace 1). Subthreshold stimulation that does not produce APs is not accompanied by an increase in cytosolic Ca²⁺(trace 2). An electrotonic residue from an AP that fails to invade the soma also does not produce a somatic Ca²⁺transient (trace 3).