Postnatal Development of the Lumbar Para-Aortic Paraganglion

So far, a number of contradictory data have accumulated regarding not only the timing and characteristics, but also the very fact of age-related involution of the largest of the extra-adrenal chromaffin paraganglia – the lumbar para-aortic paraganglion (LPP, organ of Zuckerkandl). The aim is to investigate the features of age-related transformations of the LPP in postnatal ontogenesis. Material and methods. Using histological and histochemical methods on complete serial sections, the organ complexes of the area of location of the LPP of rats in the main periods of postnatal ontogenesis (0–1, 7–8, 14, 21 days, 1, 3, 6–8, 14 months and 2 years). Results. All newborn animals have a well-developed LPP, which contains arrays of chromaffin cells with a moderate chromaffin reaction and heterogeneous groups of slightly differentiated cells. The size and number of chromaffin cells in the LPP decrease (according to a number of signs via autophagy) while the presence of nerve cells increases from the end of the 1st postnatal week. This leads to the transformation of the LPP into a mixed chromaffin-nerve ganglion, then into a typical nerve ganglion. Chromaffin cells in the LPP area completely disappear by the 1st month. Groups of chromaffin cells with intense chromaffin reaction reappear in the LPP area nerve ganglia starting from 3 months, then their number and size increase until old age. We associate the causes of age-related LPP involution with the activation of adrenal medulla maturation during the same period and the secondary appearance and hypertrophy of chromaffin cells in the LPP area with increased stress effects during maturation and weakening of the cardiovascular system during aging. Both factors cause an increase in the level of glucocorticoids which are stimulators of the proliferation of extra-adrenal chromaffin tissue. Conclusion. The rat LPP demonstrate a pronounced age-related involution, accompanied by the replacement of chromaffin tissue by nervous tissue from the 1st to the 4th postnatal weeks. After the completion of age-related involution of the LPP, clusters of chromaffin cells appear for the second time in the nerve ganglia of this area, progressing as growing up and ages.