Figure 5.
Loss of NPY eliminates the stress-induced increase in adrenal catecholamine secretion. A, Amperometric events evoked by a 5 Hz train of 200 voltage-clamp depolarizations from chromaffin cells from NPY knock-out (k/o) control and stressed mice. Right panel are excerpts from the regions indicated by the gray bars showing the response to five depolarizing steps. Top trace, Amperometric electrode. Bottom trace, ICa. B, Cumulative amplitude distribution of amperometric events from control and stressed NPY knock-out animals (control, 2113 events; FST, 2281 events; n = 18 cells per condition). C, Cube root of event charge (from data in B) fit with two Gaussian distributions. D, Average amperometric events from a representative pair of control and experimental cells (control, 43 events; FST, 144 events). E, Secretory event number and amplitude of voltage-dependent calcium current from control and experimental cells (mean ± SEM, n = 3 paired experiments, 6 cells per treatment in each experiment). F, Normalized plot of the number of amperometric secretory events occurring during a train of 200 voltage-clamp depolarizations. The right panel is an expansion of the cumulative release curve from the first 10 depolarizations. Compare this with the equivalent region of the cumulative release curve from wild-type animals (Fig. 3G). Cntl, Control. G, Time of occurrence of the amperometric release events relative to each depolarizing voltage-clamp step. Each depolarization (indicated by the gray bar) was a 20 ms voltage step from −80 to 0 mV repeated 200 times at 5 Hz. H, Plot of the time of occurrence of the amperometric events indicates that the FST does not change the probability of release in mice lacking NPY (quantified as the fraction of total events that occur during 1 ms time bins, mean ± SD, n = 3 separate experiments, 6 cells per treatment per experiment). Data in F–H are from cells shown in B. ns, Not significant.