Fluorescence measurement of lesion-induced fiber growth. II. Measurement of sympathohippocampal sprouting using a new microfluorometric method.

A microfluorometric (MF) method for measuring areal density and fiber intensity of fluorescent catecholamine fibers and varicosities was described in the previous paper. This method was then used to quantify sympathetic growth observed in the hippocampus after damage to the septal area. Because this MF method does not distinguish between catecholamine fibers of central and peripheral origins, several different ways to measure sympathetic ingrowth were used. First, the ingrowth was measured in subiculum, which has a naturally sparse innervation of central catecholamine fibers. Second, multivariate analyses were used to distinguish between: (1) sham animals -- with central innervation; (2) animals with septal lesions -- with central and peripheral innervation; and (3) sympathectomized septal animals -- with peripheral innervation removed. Finally, a polynomial regression analysis was used to identify the changes in catecholamine innervation over time that suggested a decrease in central innervation with a subsequent increase in the ingrowth of sympathetic fibers. The resulting data converge in support of the objective microfluorometric measurement of sympathohippocampal ingrowth in our histofluorescence preparations.