Fig. 5.

Action potential-evoked regenerative rises in free calcium in response to muscarinic stimulation. Action potentials were evoked by a single or train of current injections as shown in the traces at theleft. Calcium transients, plotted as ΔF/F, recorded over the nucleus, extranuclear soma, and dendrite are shown to the right.a, the calcium transient in response to a single action potential (thin traces) was reduced in the presence of muscarine (thick traces). b, In response to a 200 msec current injection, which evokes a train of action potentials, the calcium response showed a regenerative amplification in the nucleus, extranuclear soma, and the proximal dendrite during muscarinic stimulation. c, The amplification is not attributable to increased number of action potentials evoked in muscarine because a similar amplification is seen when only four action potentials are evoked at a frequency of 20 Hz. The responses in control Ringer's solution are shown as thin traces, and the response in the presence of muscarine is shown as a thick trace. Note that, in the presence of muscarine, the rising phase of the calcium transients greatly outlast the action potential train, indicated by the solid bar below thetraces.