Morphological Changes in Hippocampus and Prefrontal Cortex of Confined Sows with Prolonged Pupillary Light Reflex

Abstract

Human depression patients often show abnormal pupillary reflex with morphological changes in hippo campus and prefrontal cortex. This study aimed to find the relationship between the prolonged pupillary light reflex (PLR) which had been shown by confined sows with chronic stress or depression and morphological changes in brain, in order to provide theoretical basis for that the confined environment should lead to sows' depression. A total of 637 sows of Durac, Landrace and Large White breeds with various parities were observed, and the pupil light reflex (PLR) was measured and the actual pupillary light reflex time (PLRT) were recorded. All the PLRTs were grouped based on the results of confidence interval: t>10% as group A, 5%<t<10% as group B, 1%<t<5% as group C and t<1% as group D. Three individuals were randomly selected from each group (12 sows in total) and the white tissues of hippocampus and the prefrontal cortex were prepared for HS staining slices (three slices/per tissue) for observation on tissue structure and pathological changes with high magnification (400X) of electronic microscope. The results showed that in group A (t>10%) pathological change was found in hippocampus, however, as PLRT increased from group B to group D, pathological changes in hippocampus tissues tended to be deteriorated with the increase of inflammatory cells and nuclear pyknosis phenomena. The same as those shown in hippocampus as the increasing of PLRT from groups A to D, more inflammatory cells appeared in prefrontal cortex for groups B and D. The results suggested that the tissue lesions of hippocampus and prefrontal cortex of the confined sows with prolonged PLRT might be the results of chronic stress or depression.