Figure 7. Parasympathetic vasoactive intestinal peptidergic innervation of vertebrobasilar arteries is reduced in the hypertensive rat.

The peptidergic VIP parasympathetic labelling is similar to that seen for VAChT. A deficit is evident in both juvenile (top) and adult SHRs (▪) compared to age‐matched Wistar rats (▫). Notably the decrease is prior to the onset of hypertension. The effect of strain, but not region, is significant in juveniles and adults. Regional differences are indicated on the figure. ^** P < 0.01, ^*** P < 0.001. Within strain comparisons found significant difference in fibre densities in the Wistar rats across age (P < 0.001) but not with respect to region. Post hoc differences in age for each region are indicated by ^† on the adult panel. ^†† P < 0.01. In SHRs there was no effect of age or region, but a significant interaction (P < 0.05) between the two groups. VIP fibre densities are significantly higher in Wistar adult rats than juveniles, but no such change is observed in SHRs. Representative fluorescence microscopy images of area BAp for each group labelled with the peptidergic parasympathetic marker α‐VIP‐594, excerpts of adult innervation at higher magnification (far right). [Color figure can be viewed at http://wileyonlinelibrary.com]