Changes in Duodenal Lymphoid Structures in Rats with Different Levels of Behavioral Activity Treated with Delta Sleep-Inducing Peptide and during Acute Emotional Stress

The effects of delta sleep-inducing peptide (DSIP) on intestinal lymphoid formations were studied. Experiments were performed on 42 male Wistar rats which had previously been tested in an open field. The results of this test were used to divide the rats into behaviorally active (predicted to be stress-resistant) and passive (stress-susceptible) animals. Stress was applied by restraining the animals in boxes with electrical stimulation of the back for 1 h. Administration of i.p. DSIP to rats led to decreases in the number of eosinophils in animals of all experimental groups. In active rats of the control group, administration of DSIP produced increases in the numbers of small and intermediate lymphocytes which were greater than increases in passive rats. After acute stress, behaviorally active rats showed increases in the number of lymphoid cells, mainly due to small and intermediate lymphocytes. In passive rats, stress and injection of DSIP were followed by increases in the numbers of plasma cells in all the duodenal mucosal structures studied.