The effects of intracerebroventricularly applied ghrelin on thymocytes and thymic architecture in rats of different ages

Abstract

Ghrelin positively influences the total number of thymocytes and size of the thymus in 14-, 20- and 24-month-old rats. We examined the effect of centrally-applied ghrelin on thymus weight and structure in Wistar rats of different ages. The study included 30 male Wistar rats of three age groups: peripubertal (5-week-old rats), young (2 months) and adult (6 months). The animals of each age group were divided into control and experimental groups that were administered intracerebroventricularly (ICV) 1 ?g ghrelin/5 ?L saline daily for five consecutive days. Following treatment, the thymuses were isolated, weighed and processed for stereological analysis by the point-counting method. The average weights of the thymuses were significantly higher in the ghrelin groups with respect to control rats (5 weeks: 444.90?18.03 vs 365.00?18.63; 2 months: 354.30?13.77 vs 257.00?9.60; 6 months: 365.00?15.90 vs 225.00?7.03, p<0.01). The absolute volume of lymphoid tissue was significantly higher in the ghrelin groups (5 weeks: 392.85?16.94 vs 294.48?33.37; 2 months: 309.30?12.10 vs 216.62?10.72; 6 months: 222.70?11.41 vs. 114.33?16.48, p<0.01). Ghrelin treatment restored thymic structure by increasing medullary cellularity, improving thymic medullary architecture and providing a clearer delineation between the cortex and medulla. This study shows the positive effects of centrally applied ghrelin on suppression of thymus atrophy, its weight and architecture.