Development of NOS-containing neuronal somata in the rat kidney

An investigation of the changes in size, number and distribution of NOS-containing neuronal somata in the rat kidney was undertaken. The immunoperoxidase method for the staining of NOS and the histochemical method for the demonstration of NADPH-d were applied to serial thick sections (100 microns) of whole kidneys. Animals at embryonic day 14 (ED14), ED16, ED18, ED20, at birth (PD0), and at postnatal days 4 (PD4), PD12, PD21 and PD35 were studied. NOS-containing neuronal somata were observed by the 20th day of gestation in some kidneys and were consistently seen at birth. They were usually seen in groups of separated neuronal somata or in tight clusters. The neuronal somata were often attached or embedded in nerve bundles. As the kidney developed, the number of neuronal somata separated from each other increased, while the number of clusters remained relatively constant. The size of the neuronal somata increased with development. There were highly significant statistical differences in the size of the neuronal somata between all groups, except between PD12 and PD21. The distribution of neuronal somata at birth was similar to that of the adult. They could be found, (a) at the free renal pelvic wall; (b) in the connective tissue at the angular space between the renal pelvis and the renal parenchyma (SPP); and (c) along the interlobar vessels. At birth and in the early stages of development, the greatest number of neuronal somata were located at the renal pelvis. In the later stages of development, more neuronal somata appear in the connective tissue between the renal pelvis and the renal parenchyma. The location of NOS-containing neuronal somata suggests that they might have a modulatory role on the sympathetic and sensory renal nerves all through development.