Uptake of dopamine and subsequent ultrastructural changes in gonadotrophs of the laying hen

Intraperitoneally injected dopamine was taken up selectively into gonadotrophs of the laying hen and induced different changes in the ultrastructure of gonadotrophs according to the stages of the ovulatory cycle, i.e. the gonadotrophs exhibited an accumulation of secretory granules in the cytoplasm both at 18-19 and 3-4 h before ovulation, whereas they showed a conspicuous decrease of secretory granules and also concentration of lysosomes near a mass of the granules at 7-8 h before ovulation. These results suggest that dopamine may play a role in inhibitory effects on the secretory activity of the laying hen gonadotrophs both by obstructing the discharge of secretory granules from the cells and by activating lysosomes which autophagocytise the granules within the cells.