Obestatin, a peptide derived from the same prohormone that Ghrelin, opposes Ghrelin´s effects.
Carlini, V, Gaydou, R and de Barioglio, S.
Dpto de Farmacología. Fac de Ciencias Químicas. U.N.C.
Medina Allende y Haya de la Torre. Ciudad Universitaria, 5000-Córdoba. Argentina. E-mail: vcarlini@mail.fcq.unc.edu.ar
Ghrelin (GR), a circulating appetite-inducing hormone, is derived from a prohormone by posttranslational processing. Another peptide, named obestatin (O) also derived from proghrelin has been recently isolated. In a previous work we have demonstrated that GR induces anxiety-like behavior and increases memory retention. In the present series of experiments the effects of icv O administration (0.3 and 3nmol/rat) upon memory retention, anxiety-like behavior and food intake were studied, using step down (SDT), object recognition test (ORT) and elevated plus maze test (EPMT). O icv injection exerts an anxiolytic effect as suggest the increased % of entries (61.7 ± 2.7 vs. 33.3 ± 1.5) and time spent in the open arms in EPMT (72.1 ± 4.2 vs. 25.8 ± 1.7) for the O 3nmol/ rat vs. control respectively. The O injection during the light or dark period resulted in a decrease on food intake during the periods 0-1, 1-2 and 4-24 h after administration. The rats also exhibit an increased performance for memory retention. O increases in a dose dependent manner the latency time in the SDT (O 3nmol/ rat 115 vs. Ctrl 24) and increases the % of time of exploring novel object (ORT) (O 3 nmol/rat 78.9 ± 2.74 vs Ctrl 61.5 ± 4.0). In conclusion, these results suggest that the O effects on anxiety-like behavior and feeding are opposite to those of GR, but are similar on memory retention.
