Figure 5.
Synaptic transmission from the pacemaker neurons is not essential for proper phase of LP and PY neuron activity. Calibration: A, B, 5 mV; C, 2.8 nS, 1 nA, 10 mV. A, Simultaneous recordings of PD, LP, and PY in control saline. Floating bars in the top panel represent the average ± SEM phase of activity (n = 10) for that preparation. The phase diagram in the bottom panel is the average of five preparations. The resting membrane potentials were –57 mV for PD, –55 mV for LP, and –56 mV for PY. B, Bath application of TEA and PTX removes the biological chemical synapses within the STG. Only PD maintained rhythmic oscillatory activity. The resting membrane potentials were –55 mV for PD, –46 mV for LP, and –44 mV for PY. C, While in PTX/TEA, artificial synapses that mimic the biological AB/PD synapses were activated for the same duration and period as that of the PD neuron in control conditions using the dynamic-clamp technique (DC). The synaptic conductance (gsyn; top trace) as well as other parameters of Isyn activated in the LP and PY neurons were identical. The value of Isyn injected in the LP (ILP; third trace) and PY (IPY; last trace) neurons was calculated through continuous reading of the membrane potential of these neurons. In response to the artificial synaptic inputs, the LP and PY neurons maintained the correct relative phase of activity (floating bars). Phase was calculated using the presynaptic voltage signal as reference. Each of the first floating bars (in top and bottom panels) is meant to represent the phase of the artificial presynaptic voltage signal. As in A, the phase diagram in the bottom panel represents the average of five preparations. The resting membrane potentials were –46 mV for LP and –44 mV for PY. D, The time delay between the LP and PY neuron burst onsets increased with the I-B dur of Isyn, but this increase was not statistically significant. The solid diagonal line shows the best linear fit of the data.