Morphofunctional characteristics of large-celled hypothalamic nuclei in experimental fecal peritonitis with oxytocin administration

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DOI: 10.22138/2500-0918-2026-23-3-367-377

K.S. Nemaltseva, D.V. Volkov, A.A. Stadnikov, V.S. Tarasenko

Orenburg State Medical University, Orenburg, Russian Federation

Abstract

The aim of this study is to determine the morphofunctional characteristics of the nonpeptidergic hypothalamic pituitary neurosecretory system under conditions of experimental fecal peritonitis with oxytocin administration. Material and methods: the experimental study was conducted on 33 outbred, sexually mature, white male laboratory rats weighing 280-300 g in two series of experiments. The experimental fecal peritonitis was modeled by injecting 30% autogenous fecal suspension into the animals' abdominal cavity at a dose of 0.5 ml per 100 grams of the animal's body weight. The hypothalamic fragments were studied at the light optical and ultrastructural levels. An immunohistochemical method was used to study the material. When laboratory animals from the first series of the experiment (without administering oxytocin) were removed from the experiment on the 3rd day, it was revealed that the state of prolonged hypersecretion of neurosecretory cells was on the verge of exhaustion. In the supraoptic and paraventricular nuclei, markedly hypertrophied, «light» and swollen perikaryons were observed. Immunohistochemical studies showed that under conditions of fecal peritonitis, the number of apoptotic neurosecretory cells increases, with a simultaneous decrease in bcl2 positive cells. Results and discussion. An assessment of neurosecretory cell status in the hypothalamic nuclei of rats following intraperitoneal injection of fecal suspension revealed functional activity across all experimental series. On day 2 post-injection, the nuclei and nucleoli of «light» (functionally active) neurosecretory cells were enlarged. After 24 hours, the supraoptic and paraventricular nuclei were predominantly composed of lightly stained neurosecretory cells. By day 3, however, the prolonged hypersecretion had brought these cells to the verge of exhaustion. At this stage, the supraoptic and paraventricular nuclei contained highly hypertrophied, swollen «light» perikaryons with rounded karyolymphas showing numerous chromatin-poor invaginations. Immunohistochemical analysis demonstrated that fecal peritonitis increased the number of apoptotic neurosecretory cells while reducing the bcl2-positive population. Concurrently, the release of neurosecretory substances via the hypothalamic-pituitary system was blocked at the level of neurohypophysis, leading to the accumulation of large, often droplet-like inclusions within the axons—a specific form of neurohormone storage. Under these conditions, axon terminals predominantly assumed cone- or bulb-shaped dilations. In contrast, administration of oxytocin corrected the morphofunctional state of the hypothalamic magnocellular nuclei, restoring the normal structural organization. Ultrastructural examination of axons and their terminals indicated synchronized synthesis and release of secretory granules into the bloodstream. Mitochondria and the endoplasmic reticulum showed no signs of destruction, while secretory granules regained their typical architecture (electron-dense core, clear halo, and surrounding membrane). These changes were reflected in the normalization of granule release at the median eminence and restoration of axovasal contacts in the neurohypophysis. Notably, oxytocin also appeared to suppress the apoptotic trend, as evidenced by increased synthesis of the anti-apoptotic protein bcl2.

Keywords: hypothalamus, fecal peritonitis, oxytocin, neurosecretory cells, large-cell nuclei of the hypothalamus

There is no conflict of interest.

Contact details of the corresponding author

Ksenia S. Nemaltseva
ksminenko@yandex.ru
Received: 07.05.2026

For citation

Nemaltseva K.S., Volkov D.V., Stadnikov A.A., Tarasenko V.S. Morphofunctional characteristics of large-celled hypothalamic nuclei in experimental fecal peritonitis with oxytocin administration. Vestn. Ural. Med. Akad. Nauki. = Journal of Ural Medical Academic Science. 2026, Vol. 23, no. 3, pp. 367-377. DOI: 10.22138/2500-0918-2026-23-3-367-377 (In Russ.)

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Authors

Ksenia S. Nemaltseva
Assistant at the Department of Hospital Surgery
ksminenko@yandex.ru
ORCID ID: 0000-0003-3144-4870

Dmitry V. Volkov
 Dr. Sci. (Med.), Professor
Head of the Department of Hospital Surgery
 d.v.volkov@list.ru
ORCID ID: 0000-0002-5253-5379

Alexander A. Stadnikov
 Dr. Sci. (Biol.), Honored Scientist of the Russian Federation
Professor of the Department of Histology, Cytology and Embryology
alexander.stadnikov@yandex.ru
ORCID ID: 0000-0003-3144-4870

Valery S. Tarasenko
 Dr. Sci. (Med.), Honored Doctor of the Russian Federation
Professor of the Department of Hospital Surgery
k_gspsurv@orgma.ru
ORCID ID: 0000-0003-1491-9213

Orenburg State Medical University
Orenburg, Russian Federation

 
 
 
 

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