Neuroendocrinology
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In this study, we examined (i) the preprandial, postprandial and starvation-induced changes in the preproghrelin mRNA expression and serum ghrelin levels, and (ii) the effects of intracerebroventricular and intraperitoneal administration of ghrelin on food intake in goldfish. Slot blot analysis revealed a significant postprandial decrease in preproghrelin mRNA expression in the hypothalamus (1 and 3 h after feeding) and gut (3 h after feeding). A similar postprandial decrease (1 and 3 h after feeding) in serum ghrelin levels was also detected. ⋯ Serum ghrelin levels were significantly elevated on days 3 and 5 of starvation. Intracerebroventricular injections of n-octanoylated ghrelin-like peptides (gGRL([1-12])) (10 ng/g body weight) and human ghrelin (1 and 10 ng/g body weight) and intraperitoneal injections of n-octanoylated gGRL([1-12]) (10 ng/g body weight), gGRL([1-19]) (100 ng/g body weight) and human ghrelin (10 and 100 ng/g body weight) stimulated food intake in goldfish. The patterns of synthesis, secretion and actions indicate that ghrelin is an orexigen in goldfish.