Figure 4. Loss of sympathetic NPY enhances circulating NE without affecting neuron activity.

(A-D) Similar numbers of c-FOS-positive sympathetic neurons in CG-SMG from 6–8 week-old control and NPY cKO mice housed at room temperature (RT, 26°C). Cold exposure (4°C, 1 hr) increases the number of c-FOS-positive sympathetic neurons in both control and mutant ganglia. Scale bars, 50 μm. (E) Quantification of c-FOS-positive sympathetic neurons in control and mutant CG-SMG at RT and in response to cold exposure (4°C, 1 hr). Data are presented as means ± s.e.m from n=6 animals for control mice at RT, and n=3 animals for all other conditions. ****p p<0.0001; two-way ANOVA, Tukey's multiple comparison test. (F) Plasma NE levels are significantly elevated in NPY cKO mice compared to control animals at room temperature (26°C). Cold exposure (4°C, 2 hr) significantly increases circulating NE in control, but not NPY cKO, animals. Data are as means ± s.e.m n=11 control and 20 mutant mice. *p<0.05; two-way ANOVA, Tukey's multiple comparisons. (G) Th mRNA is increased in adrenal glands, but not in sympathetic ganglia, in NPY cKO mice relative to control animals as shown by qPCR analysis. Results are means ± s.e.m from n=3 mice per genotype for SCG, 4 for CG-SMG, and 6 for the adrenal glands. *p<0.05; one sample t-test. (H) TH immunofluorescence is increased in adrenal chromaffin cells in NPY cKO mice relative to control animals, indicating an increase in TH protein level. Scale bar, 50 μm.