Comparison of Neuron Number in the Superior Cervical Ganglion of SHR and WKY Rats

The spontaneously hypertensive (SHR) rat is a genetic model for the study of essential hypertension. Blood pressure in the male SHR is elevated compared to the female SHR and to both sexes in the normotensive Wistar Kyoto (WKY) strain. Compared to the WKY the cerebral and mesenteric vasculature of the male SHR is hyperinnervated by sympathetic nerves and neonatal sympathectomy in the SHR reduces blood pressure. The objective of this experiment was to investigate the relationship between sex and strain differences in blood pressure and neuron number in the superior cervical ganglion (SCG). To this end sex and strain differences in ganglion volume, cell number and density and mean soma area in the SCG of SHR and WKY rat strains were measured. Ganglia were fixed with 4% paraformaldehyde in 0.01M sodium phosphate (pH 7.4) by cardiac perfusion and embedded in paraffin. Sections were cut at 6μ and stained with toluidine blue and digital images were captured for image analysis (ImageJ, Scion Corp, Frederick, MD). Sex differences were observed in both strains for neuron number, cell density, ganglion volume and mean soma size, but no strain differences were found for any of the parameters measured. These data suggest that blood pressure differences between strains are not related to neuron number. This work was supported by a Faculty Grant from the University of Akron.