Figure 6. Representative current-clamp recordings showing PrRP-induced depolarization and increase in spontaneous firing in gastric-projecting DMV neurones.

A1 (upper trace), superfusion of PrRP (300 nm) produced a small membrane depolarization, accompanied by a marked increase in spontaneous discharge that persisted for many minutes following washout of the peptide. (lower trace). A segment of same recording displayed at faster time sweep illustrates slowly developing depolarization of 4 mV in response to PrRP. A2, administration of TTX (2 μm) blocked spontaneous action potential firing in the same neurone, and in its presence PrRP had no effect on the membrane potential or spike discharge. Note different time scales for upper and lower traces. B, current-clamp recording from another gastric-projecting DMV neurone showing attenuation of the excitatory effects of PrRP on membrane potential and spike firing during coadministration of the glutamate receptor antagonists APV (50 μm) and CNQX (20 μm). The excitatory effects of PrRP were re-established and the elevation in spike firing increased further following washout of APV and CNQX from the bath. Downward deflections in the trace represent electrotonic potentials evoked in response to the passage of constant hyperpolarizing current pulses through the electorde that were used for measurement of membrane conductance. Holding potential for both neurones was −54 mV. Slow sampling rate of digitization resulted in truncation in the amplitudes of some action potentials.