Dopamine Release in the Ventromedial Hypothalamus of Growing Chickens Decreases when They are Fed a Lysine Devoid Diet

Abstract

Deficiencies of single essential amino acids decreases food intake and this is likely to be involved in the central nervous system. Central mechanism underlying the decreased food intake induced by amino acid deficiency in chickens remains to be elucidated. We determined the hypothalamic interstitial monoamines (dopamine, norepinephrine and serotonin) with brain microdialysis technique to investigate whether hypothalamic monoaminergic system is associated with the reduction of food intake in growing chickens on a lysine devoid (LD) diet (a purified diet with a crystalline amino acid mixture not containing lysine as a sole source of nitrogen). Microdialysis probes had been inserted at the ventromedial (VMH) and lateral hypothalamus (LH) before presenting the diets. Perfusate was collected every 30min from two hours before feeding the LD diet to five hours later. Monoamines in the perfusate were determined using a high performance liquid chromatography. Chickens on the LD diets ate as much as the control chickens for early three hours, but the former ate less amount of food than the control one four and five hours after presenting the diet. Out of the ventromedial hypothalamic monoamines, dopamine level of the LD group started to decrease from the basal line one hour later and was lower than that of the control group 3.5 hours and afterward. Compared with the control group norepinephrine level of the LD group showed no change. Serotonin level was lower in the LD than control groups at one and four hours. The level of monoamines in the lateral hypothalamus did not differ between the dietary treatments. In conclusion, the present results demonstrate that feeding the lysine devoid diet decreased DA release in the VMH not in the LH before food intake started to decrease.