A method to measure the distribution pattern of specific nerve terminals in sampled regions. Studies on tyrosine hydroxylase LHRH, TRH and GIH immunofluorescence.

Abstract

Using the indirect immunohistochemical technique, a tyrosine-hydroxylase related immunofluorescence was studied in the [rat] nucleus caudatus, tuberculum olfactorium and median eminence and luteinizing hormone releasing hormone [LHRH], thyroid stimulating hormone releasing hormone [TRH] and growth hormone release inhibiting hormone [GIH]-related immunofluorescence in the median eminence. Quantitative fluorimetry was used to measure the specific immunofluorescence. A method was developed to quantitate overall fluorescence intensity in a sampled field (which mainly is related to density in the present analysis of tyrosine-hydroxylase, LHRH, GIH and TRH positive terminals), distribution of these terminals and overall lack of uniformity of their distribution is a sampled field. The method is based on measurements of fluorescence intensity in concentric areas of increasing radius in a sampled field. Influence of photodecomposition apparently was negligible. In log-log graphs with the radius on the X-axis and intensity on the Y-axis, the difference in intercept on the Y-axis between specific and unspecific fluorescence apparently reflected mainly the fluorescence density, while the innervation pattern could be studied by comparing for each successive increase in radius the observed slope with the theoretical slope (best fit line slope). A quantitative overall evaluation of the lack of uniformity of innervation was obtained by the sum of the absolute values for the differences in observed and theoretical slopes, divided by the number of these differences. Using this quantitative approach it is possible: to make quantitative comparisons in many different areas of densities and patterns of nerve terminals containing one and the same transmitter; to make quantitative comparisons in one and the same area of densities and patterns of nerve terminals belonging to different pathways but containing one and the same transmitter, provided measurements are made before and after a selective lesion of one of these pathways; to make quantitative comparisons in one and the same area of densities and patterns of nerve terminals containing different transmitters; to obtain indirect support whether or not a synaptic interaction can occur between 2 types of nerve terminals in the same region or if they can end on the same postsynaptic dendrites or the same cell body. A significant similarity in distribution of LHRH and dopamine and possibly between GIH and dopamine nerve terminals in the lateral external layer of the median eminence was demonstrated. An axo-axonic interaction may exist between dopamine and GIH and particularly dopamine and LHRH-positive terminals in the median eminence.