Age-dependent patterns of somatostatinergic neurons in sympathetic paravertebral ganglia

Abstract

Aim. We aimed to determine the content of neurons expressing somatostatin (SST) and their colocalization with  cells expressing tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in the cranial cervical ganglion (CCG) and celiac  plexus in rats.  Material and methods. We used 30 white male Wistar rats of six age groups (5 rats per group): newborn pups, 10-,  20-, 30-, and 60-day-old pups, and 24-month-old pups. We incubated their ganglia sections with primary antibodies  against SST, NPY, and TH, as well as with secondary antibodies conjugated with fluorochromes. We evaluated the  ratio between immunoreactive (IR) neurons with a visible nucleolus and excessive fluorescence and the total number  of neurons, as well as the average cross-sectional area, by ImageJ software (NIH, USA).Results. SST-IR neurons were not found in the CCG. However, the immunoreaction (as granules) was revealed in  most perikaryons at the celiac plexus for SST and NPY with a rather homogeneous distribution for TH. The ratio of  ST-IR neurons reached 33% in pups, doubled during the first month of life, and then remained constant (70–73%).  No statistically significant differences were found between the ratios of SST-IR neurons of the cranial mesenteric  ganglion (CMG) and celiac ganglion (CG) for all age groups. From the moment of birth to 60 days of life, the  average cross-sectional area of SST-IR neurons in the CG and CMG increased by 3.4–3.9 times and then did not  change until 24 months. From the 20th day of life, the average cross-sectional area of SST-IR neurons in the CG  was significantly higher than that in the CMG. All SST-IR neurons in all age groups expressed TH, while 90–94% of  neurons expressed NPY. Conclusions. The content of ST-IR neurons in different sympathetic nodes is not the same: they are absent in the  CCG, and their ratio and area in the celiac plexus increase during early postnatal development. This may be due to  the peculiarities of innervated target organs.