AUTONOMIC PREGANGLIONIC INNERVATION TO UTERINE WALL

AN HRP STUDY ON THE RAT

Abstract

Using the horseradish peroxidase (HRP) technique, the autonomic preganglionic neurons which project onto the uterine wall were studied on the female rat.
Following injection of an HRP solution into the uterine wall, the intramural postganglionic neurons were discovered in the myometrium near the basement of the bicornuate uterus.
In 6 experiments, an HRP solution was injected into the site of the intramural postganglionic neurons. After a survival period of 2 days, the lumbar and sacral cords were serially sectioned and processed for histochemical demonstration of HRP.
Of the total of 3939 HRP labeled cells, 885 (22%) were observed in the lumbar regions (L1-L3) and 3054 (78%) in the sacral regions (L6-S2). The HRP labeled cells were distributed in 4 nuclei ; 1. nucleus intermediolateralis pars principalis (ILp); 2. nucleus intermediolateralis pars funicularis (ILf); 3. nucleus intercalatus (IC); 4. nucleus dorsalis commissuralis (DCN).
The total of 885 HRP labeled cells observed in the lumbar regions were distributed over 4 nuclei : 1. 621 (70%) in DCN ; 2. 215 (24%) in ILp ; 3. 34 (4%) in IC ; 4. 15 (2%) in ILf. This indicates the DCN is the major site of sympathetic preganglionic neurons projecting onto the uterine wall. On the other hand, the total of 3054 HRP labeled cells observed in the sacral regions were distributed over 3 nuclei : 1. 2757 (90%) in ILp ; 2. 213 (7%) in IC ; 3. 84 (3%) in ILf. This indicates the ILp is the major site of parasympathetic preganglionic neurons projecting onto the uterine wall.
The laterality of distribution of the HRP labeled cells was clearly recognized in the sacral regions, but not in the lumbar regions. This indicates the sympathetic preganglionic neurons innervate bilaterally, but the parasympathetic ones ipsilaterally.
According to the criteria whether or not the HRP labeled cell can be expressed by oval, fusiform, pyramidal or multipolar form, the HRP labeled cells were classified into 2 groups, the morphologically classifiable (47% of the total) and unclassifiable (53% of the tatal). In common with both sympathetic and parasympathetic preganglionic neurons, the majority of the HRP labeled cells showed fusiform, and the minority of them showed oval, pyramidal and multipolar. The relation between form and role of the autonomic preganglionic neuron may be an important problem which should be answered in future.