Intravenous Orexin Reduces LH Secretion in Castrated Camelus Dromedaries Fed a Sub-maintenance Diet

It has been shown that orexin has an inhibitory effect on gonadotropin secretions in non-ruminant animals. The goal of this study was to determine whether orexin affects LH, and FSH secretions in the camel, as a pseudo-ruminant animal, under different dietary energy content. Sixteen castrated camels were randomly divided into 4 groups. Animals in groups 1 and 2 were fed 100% and animals in groups 3 and 4 were fed 50% energy content in their diet for 20 days. After 20 days, animals in groups 1 and 3 received infusions of 1 $\mu{g}$ orexin and groups 2 and 4 received infusions of 2 $\mu{g}$ orexin into their jugular vein. Blood samples were collected from the jugular vein every 20 minutes from 4 h before the first infusion of orexin until 4 h after the last orexin infusion. Lower dietary energy intake and infusions of 2 $\mu{g}$ but not 1 $\mu{g}$ orexin significantly (p<0.01) decreased the mean plasma concentrations and pulse amplitudes of LH of the animals. Infusion of 1 and 2 $\mu{g}$ orexin did not change the secretions of LH of the animals fed NE. Different energy dietary intake and infusion of 1 and 2 $\mu{g}$ orexin did not change the mean plasma concentrations of FSH of the animals in all groups. Infusions of 1 and 2 $\mu{g}$ orexin significantly (p<0.01) decreased the glucose levels of animals fed LE but not in NE fed animals. Additionally, plasma glucose levels of the LE-fed animals in groups 3 and 4 were significantly (p<0.01) lower than those of the animals in groups 1 and 2 fed NE diet. The results of this experiment indicated that orexin may negatively affect LH and FSH in camels with negative energy balance, but not in those with positive energy balance.