Central and peripheral methylamine-induced hypophagia is mediated via nitric oxide and TAAR1 in neonatal layer-type chicken

Abstract

The aim of the current study was to determine effects of intracerebroventricular (ICV) and intraperitoneal (i.p.) administration of Methylamine (MET) and possible interactions with nitric oxide (NO) and TAAR1 pathways in 24-h fasted (FD24) and ad libitum layer-type chicken. In experiment 1, FD24 chicken ICV injected with MET (15, 30, 45, 60 and 75 μg). In experiment 2, ICV injection of MET (15, 30, 45, 60 and 75 μg) was injected in the ad libitum birds. Experiments 3–4 were similar to experiments 1–2, except chicken i.p. injected with MET (15, 30, 45, 60 and 75 mg/kg). In experiment 5, FD24 birds ICV injected with l-NAME (NO synthesis inhibitor, 100 nmol), MET (75 μg) and co-injection of l-NAME + MET. Experiment 6 was similar to experiment 5, except, ad libitum birds received injections. In experiment 7, FD24 chicken i.p. injected with l-NAME (100 mg/kg), MET (75 mg/kg) and co-injection of l-NAME + MET. In experiment 8, FD24 birds ICV injected with RO5256390 (selective TAAR1 agonist, 10, 20 and 40 μg). In experiment 9, ad libitum birds ICV injected with RO5256390 (10, 20 and 40 μg). In experiment 10, FD24 birds ICV injected with RO5256390 (10 μg), MET (75 μg) and their co-injection. Experiment 11 was similar to experiment 10, except, ad libitum birds received ICV injections. In experiment 12, FD24 chicken i.p. injected with RO5256390 (2.5, 5 and 10 mg/kg). In experiment 13, FD24 chicken i.p. injected with RO5256390 (2.5 mg/kg), MET (75 mg/kg) and RO5256390 + MET. Then cumulative food intake was determined until 120 min after injection. According to the results, ICV injection of MET decreased food intake in FD24 and ad libitum chicken (P < 0.05). MET (i.p.) diminished food consumption in fasted (P < 0.05) but not in ad libitum chicken (P> 0.05). Co-injection of the l-NAME + MET significantly decreased MET-induced hypophagia in FD24 and ad libitum chicken (P < 0.05). MET-induced hypophagia (i.p.) weakened by l-NAME in FD24 chicken (P < 0.05). RO5256390 decreased food intake in FD24 and ad libitum chicken (P < 0.05). Co-injection of RO5256390 + MET increased MET-induced hypophagia in FD24 and ad libitum chicken (P < 0.05). RO5256390 decreased food intake in FD24 chicken (P < 0.05). Co-injection of the RO5256390 + MET amplified MET-induced hypophagia in FD24 chicken (P < 0.05). Based on the findings, MET-induced hypophagia is mediated via NO and TAAR1 pathways on food intake in layer chicken.