Study of the selectivity of the impregnation of neurons by the Golgi method

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Abstract
The selectivity of the impregnation of neurons by the Golgi method was examined by comparing Nissl‐stained specimens with Golgi‐stained specimens in terms of the somatic orientation, cross‐sectional area, and long and short axes of the soma in the ventromedial hypothalamic nucleus (VMH) and lateral hypothalamic area (LHA) of 5‐week‐old rats. With regard to somatic orientation, we made comparisons directly between the Nissl distribution pattern and the Golgi pattern. The two distribution patterns did not differ significantly in either VMH or LHA (Smirnov test, P > 0.05). For somatic cross‐sectional area and diameter (long and short), a mean value of every 10% of the total frequency was estimated for each histogram; the histogram was segmented into 10 percentile frequency domains, and a mean value for each domain was estimated. A linear regression was calculated between Golgi mean values and Nissl's at the same place. By use of the linear regression, all of the observed values on Nissl sections for somatic cross‐sectional area and diameter were transformed into their corresponding Golgi values. The frequency distribution of these transformed Nissl values was compared with that of the actually observed Golgi values. There was a high degree of similarity between the two distribution patterns in all regions examined for long and short diameters as well as cross‐sectional area of the soma (Smirnov test, P > 0.05). These findings suggest that the sampling of VMH and LHA neurons in the Golgi method used in the present study is similar to the corresponding sampling in Nissl preparation. The result thus provides evidence that the Golgi method impregnates neurons nonselectively, at least hypothalamic neurons. We have also demonstrated, through direct comparisons between Nissl and Golgi specimens, that somatic orientation serves as a useful parameter in the evaluation of the selectivity/nonselectivity of the Golgi method.