Figure 1.

Nicotine elicits greater changes in fluorescence indicating larger rises in intracellular calcium in LDT neurons of animals from younger age groups. (A) In the left panel an image of fura-2 loaded cells (F_{380 nm}) within the LDT, in which changes in fluorescence were examined, is shown. The white box indicates the region expanded in the right panel and the arrows indicates the same cell in both panels. The region of interest from which fluorescence was monitored is indicated by a square around the cell soma in the right panel. (B) Representative ΔF/F traces are shown of the changes in fluorescence induced by an initial (black) and a second (grey) nicotine application in a LDT cell from group A (B1), group B (B2) and group C (B3) indicating rises in intracellular calcium. The nicotine-induced change in ΔF/F is greatest in the youngest group A when compared to that elicited in the older group B and group C. The repeat application of nicotine ten minutes after the initial nicotine application induced a smaller increase in fluorescence in all three age groups, but was still higher in young animals. Nicotine application is marked by a vertical line. (C) Histogram showing the mean nicotine-induced increase in fluorescence in percent elicited in cells from each of the three age groups. The average amplitude found in group A was significantly larger than that of group B and group C. Further, in group B the average amplitude was larger than that of group C. * denotes a significance level of p< 0.05 in this and subsequent figures. (D) The percentage decrease in ΔF/F of the second compared to the first nicotine application for group A, group B and group C are shown in the histogram. There was no significant difference in the percentage decrease in ΔF/F between the three groups in response to a repeat nicotine application.