Abstract
Essential hypertension, also known as primary hypertension, does not have a recognizable primary cause. We hypothesize that sympathetic hyperinnervation might contribute to the development of hypertension. In this project, spontaneously hypertensive rat (SHR) as a rat's model of essential hypertension was used.
Since innervation of heart by sympathetic fibers is established during the early stages of heart development, comparison of the sympathetic innervation in the anterior epicardium of the left ventricle in postnatal 2, 7, 14 and 28 days old SHRs with age matched Wistar Kyoto (WKY) control rats were carried out. The sympathetic fibers were stained in SHRs and WKY rats by tyrosine hydroxylase antibodies to compare sympathetic innervation in left ventricle of hearts between SHRs and WKY rats.
It was found that 2 days old postnatal WKY rats (N=12) are about 1g heavier than the same age SHRs (N=19), but there was no difference in heart weights between these two strains at that very early life stage. However, the sympathetic fiber innervation density of the cardiac left ventricle between these two strains was significantly different. SHRs have higher sympathetic neuron fiber density in hearts at all time point studied.
Analysis of structural anatomy (density of glial cells, density of sympathetic neurons) of sympathetic superior cervical ganglion (SCG) from postnatal 8-week old WKY rats, SHRs and WKY rats treated with either saline or 6-hydroxydopamine (6-OHDA) revealed that WKY
rats have significantly higher density of glial cells and neurons than same age SHRs’ SCGs. In addition, 6-OHDA treated WKY rats have significantly higher density of glial cells and lower density of neurons than SCGs of normal WKY rats.
The data provide clues for explanations of the anatomical changes in ganglia and their contributions to changes observed in cardiac innervation of hypertensive animal model.