Endometritis decreases the population of uterine neurons in the paracervical ganglion and changes the expression of sympathetic neurotransmitters in sexually mature gilts

Abstract

Background The focus of the study was to examine the impact of the inflamed uterus on the population of the paracervical ganglion (PCG) uterus-innervating perikarya and their chemical coding. Fast Blue retrograde tracer was injected into the wall of uterine horns on the 17th day of the first studied estrous cycle. After 28 days, either Escherichia coli suspension or saline was applied to the horns of the uterus, whereas the control group received laparotomy only. Eight days after the above-mentioned procedures, uterine cervices with PCG were collected. Both macroscopic and histopathologic examinations confirmed severe acute endometritis in the Escherichia coli-injected uteri. The double immunofluorescence method was used to analyze changes in the PCG populations coded with dopamine-β‐hydroxylase (DβH) and/or neuropeptide Y (NPY), somatostatin (SOM), vasoactive intestinal polypeptide (VIP) and neuronal isoform of nitric oxide synthase (nNOS). Results The use of Escherichia coli lowered the total number of Fast Blue-positive neurons. Moreover, an increase in DβH+/VIP+, DβH+/NPY+, DβH+/SOM + and DβH+/nNOS + expressing perikarya was noted. A rise in non-noradrenergic VIP-, SOM- and nNOS-immunopositive populations was also recorded, as well as a drop in DβH-positive neurotransmitter-negative neurons. Conclusions To sum up, inflammation of the uterus has an impact on the neurochemical properties of the uterine perikarya in PCG, possibly affecting the functions of the organ.

Uterine Inflammation Changes the Expression of Cholinergic Neurotransmitters and Decreases the Population of AChE-Positive, Uterus-Innervating Neurons in the Paracervical Ganglion of Sexually Mature Gilts

“…Under optimal conditions, NO is also known for its neuroprotective properties in both central and enteric nervous systems [32,60,61]. Although studies on immature pigs' PCG have not found nitrergic perikarya [39], studies in rats and pigs indicate that the nitrergic nerve fibers supplying the uterine horn can derive from the mentioned ganglion [30,62]. The current results present a downregulation of cholinergic but upregulation of non-cholinergic, nNOS-immunoreactive neurons, which may be due to the increased importance of the nitrergic, sympathetic perikarya in a state of inflammation.…”

“…All of the necessary doses, drug trade names, and details for premedication, general anesthesia, surgical treatment, FB, and E. coli injection procedures in particular groups, have already been described in one of the authors' previous papers [30]. The procedures are briefly described in what follows.…”

“…All gilts weighed from 90 to 120 kgs and were 7-8 months of age; they were separated into either E. coli (n = 4), saline (n = 3), or control (n = 4) group. The conditions in which they were kept were thoroughly described in a previous article [30]. It is essential to note that all parameters were set in accordance with the instructions and agreement of the Local Ethical Committee in Olsztyn, Poland, and the authors used all measures necessary to keep the stress reaction to surgery and the post-surgical period at a minimum level, in accordance with Consent no.…”

“…The following examination, using a Zeiss AxioImager (Zeiss, Oberkochen, Germany) microscope containing a fluorescent module (V1 module) and appropriate filters (330-385 nm excitation filter and 420 nm barrier filter), of the examined slices allowed us to subject the FB neuron-containing sections to immunohistochemical double-labeling procedures. All of the steps, as well as the required reagents for this method, were thoroughly described in our last article [30]. As this study focuses on the parasympathetic part of the examined ganglion, antibody combinations are the only differing part (Table 1).…”

“…Papers concerning the consequences of uterine inflammation on sensory ganglia [28], as well as the caudal mesenteric ganglion (CaMG) [29], showed decreasing numbers of uterine supplying perikarya in both. A recent paper presented a severe decrease in the number of uterine perikarya in the PCG of Escherichia coli (E. coli)-treated gilts, as well as an impact of endometritis on chemical coding of the sympathetic neurons [30]. Thus, these facts combined allow us to form the hypothesis that uterine inflammation has a detectable impact on the parasympathetic, uterus-supplying neuronal cells in PCG of sexually mature gilts and alters the expression of various neurotransmitters.…”