SOMATOSTATIN-14 INDUCES DIFFERENT CHANGES IN THE THYMUS OF PERIPUBERTAL AND YOUNG ADULT RATS

Bearing in mind the role of somatostatin in thymus functions, and changes of somatostatin level and expression of its receptors during postnatal life, the aim of this study was to investigate whether centrally applied SRIH-14 induces different changes in the thymic compartments and thymocyte profile in peripubertal and young adult rats. To this end, 4- and 10-week-old male AO rats were cannulated and treated intracerebroventriculary with three doses of SRIH-14, applied every other day. In peripubertal rats, SRIH-14 decreases thymic relative weight and volume, as well as the volume of thymic compartments, especially of deep cortex, as a result of thymocytes loss by apoptosis. Also, SRIH-14 increases the percentage of immature thymocytes preceding the DPTCR__low cells (DNTCR__–/low, DPTCR__–, SPCD8TCR__–/low and SPCD4TCR__–/low), decreases the percentages of DPTCR__low and DPTCR__hi cells, while the relative proportion of CD4+/CD8+TCR__hi cells remained unaltered. In young adult rats, SRIH-14 does not lead to changes in relative thymus weight, although decreases the thymic cortex cellularity and volume. In addition, decreases the percentage of DPTCR__–/hi cells and increases the percentages of cells within DNTCR__hi and both SP subpopulations, but much more of the CD8+TCR__hi subset. These results suggest that the effects of SRIH-14 on the thymus and thymocytes subpopulations are age-dependent.