Structural changes in the nucleus ambiguus of the medulla oblongata and intracardiac ganglia in growing rats in immobilization stress.

The aim of the present work was to study qualitative and quantitative measures of histological changes in the nucleus ambiguus (NA) of the medulla oblongata and the cardiac autonomic ganglia (CAG) in growing animals in conditions of immobilization stress of different durations. Experiments were performed on 56 mongrel white rats aged 30 days. Immobilization stress was produced by placing rats in a special apparatus with a controllable internal volume for 3, 7, 15, and 30 days. The NA and CAG were studied on paraffin sections using neurohistological methods and quantitative analysis. Morphological and morphometric changes, consisting of a delay in the growth of neurocyte cell and nucleus volumes, as compared with controls, were seen both in the NA of the medulla oblongata and the CAG and were evaluated as impairments in the histogenesis of nerve tissue during postnatal ontogenesis. The extent of structural changes in these components of the autonomous nervous system was directly dependent on the duration of the experimental treatment.