FIG. 1.

CCK increases spontaneous activity of PPG neurons. A: Current-clamp recording demonstrating that bath application of 100 nmol/L CCK-8s led to an increase in spontaneous action potential firing frequency of this PPG neuron. B: A plot of the firing frequency for the recording shown in A (the part of the recording shown in A is indicated by gray background). C: Short segments of the original current-clamp recording from B at time points indicated by i, ii, iii, and iv. D: Mean data for firing frequency from experiments as depicted in A and B. CCK-8 (100 nmol/L) significantly increased firing rate. This effect of CCK-8s was occluded in the presence of the non-NMDA glutamate receptor antagonist DNQX. Number of recordings for each condition is given above the bars. *P < 0.05. E: Typical single-cell RT-PCR analysis for PPG and the CCK receptors (CCKAR, CCKBR) for three PPG neurons and controls. Agarose gel (2%) demonstrating that the 186-bp PCR product for PPG, the 285-bp PCR product for CCKAR, and the 341-bp product for CCKBR can be obtained from brain stem cDNA (1:100 dilution; positive control; indicated by arrows) with the primers specified in Table 1. In contrast, cytoplasm extracted from single cells showing eYFP fluorescence (cell1, cell2, cell3) was only positive for PPG, but not CCKAR or CCKBR (only bands for primers visible). Negative (neg) control: pipette solution without cytoplasm extracted from cell. Molecular weight ladder shows bands at 100-bp intervals.