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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.

The hypothalamus is an important regulator of autonomic and endocrine functions also involved in aging regulation. The aging process in the hypothalamus is accompanied by disturbed intracellular signaling including insulin/insulin-like growth factor-1 (IGF-1)/growth hormone (GH), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT)/the mammalian target of rapamycin (mTOR), mitogen activated protein kinase (MAPK), janus kinase (JAK)/signal transducer and activator of transcription (STAT), AMP-activated protein kinase (AMPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB), and nitric oxide (NO). In the current review, I have summarized the current understanding of the changes in the above-mentioned pathways in aging with a focus on hypothalamic alterations.

The hypothalamus is a primary regulator of homeostasis, biological rhythms and adaptation to different environment factors. It also participates in the aging regulation. The expression of neurons containing Lin28 was studied by immunohistochemistry in male rats aged 2, 6, 12, and 24 months in the tuberal region of the rat hypothalamus. We have shown for the first time the presence of Lin28-immunoreactive (IR) neurons in the ventromedial nucleus (VMH) and their absence in the dorsomedial and arcuate nuclei in all studied animals. With aging, the percentage of Lin28-IR neurons increases from 37 ± 4.7 in 2-month-old rat until 76 ± 4.6 in 6-month-old and further decreases to 41 ± 7.3 in 12-month-old rat and 28 ± 5.5 in 24-month-old rats. Many VMH Lin28-IR neurons colocalized components of insulin signaling including mTOR, Raptor, PI3K and Akt. The percentage of Lin28/Akt-IR neurons was maximal in 6-month-old and 1-year-old rats compared to 2-month-old and 2-year-old animals. The proportion of Lin28/PI3K-IR neurons significantly increased from 77 ± 1.2 in 2-month-old rat until 99 ± 0.3 in 24-month-old rats and 96–99% of Lin28-IR neurons colocalized mTOR and mTORC1 component Raptor without statistically significant differences in all studied age groups. Thus, Lin28 expresses only in the VMH neurons of the tuberal nuclei of the hypothalamus and the Lin 28 expression changes during the development together with the components of PI3K-Akt-mTOR signaling.