| As one of the plant secondary metabolites (PSMs), tannin has a great influence on animal’s feeding behavior. Melanin concentrating hormone (MCH) and orexins, neuropeptides secreted by of ventral lateral nucleus of hypothalamus, are involved in the regulation of animal appetite. Brandt’s voles are the main herbivorous animals in Inner Mongolia, they feed on the plants that contain a lot of secondary compounds. In order to explore the neural mechanism of influence of tannin acid on the feeding behavior and to provide evidence for co-evolution between animal and plant, Brandt’s voles, bred in lab, were given different dosage of tannin acid (0% for control,3% for low dosage and 6% for high dosage respectively) for different time (1h,5d,10d and 20d), continuously. Then, the mRNA transcription level of precursors protein of MCH (pp-MCH), orexins (pp-orexins) and some of their receptors was quantified by fluorescence quantitative real-time PCR, and the content of pp-MCH and pp-orexins was detected by western blot method. Meantime, the food intake, body mass and fat accumulation were also assayed. The results were as follows:After treated with tannin acid for 5,10 and 20 days, the body weight of Brandt’s vole was not different from that of control group.Tannin acid inhibited the food intake of animals when they were given it for 10 days. But tannin acid enhanced the food intake after animals were treated by it for 20 days.The fat accumulation index of Brandt’s vole was not different significantly among three groups after they were given tannin acid for 5 and 10 days. However, it was reduced when animals were treated for 20 days.The result of gene and protein expression showed that there were no change of the mRNA transcription level and content of hypothalamic pp-MCH in both of male and female voles two hours after they were treated by tannin acid, same as the expression of MCHR1 in male voles.But the expression of MCHR1 in females was inhibited in that time. Tannin acid also inhibited all of mRNA transcription level and content of hypothalamic pp-MCH, as well as mRNA transcription level of MCHR1, in both of male and female voles after they were treated for 5,10 and 20 days.Two hours after they were given tannin acid, both of male and female voles had higher hypothalamic mRNA transcription level of pp-Orexin and OX1R, but the content of their pp-Orexin was same as that in control group. All of pp-Orexin mRNA,OX1R mRNA and the content of pp-Orexin in male and female voles was lower than that of control after animals were treated by tannin acid for 5 days. But then, both of mRNA transcription level and protein of pp-Orexin, as well as OX1R mRNA transcription level increased in males 10 or 20 days after treatment. Mean while, tannin acid still reduced pp-Orexin mRNA transcription level,OX1R mRNA transcription level and the content of pp-Orexin in all of female animals after they were given tannin acid for 10 or 20 daysSo, the result showed that consecutive administration of tannin acid only inhibited the feeding of Brandt’s voles within a short time, and with the prolongation of treatment, Brandt’s voles increased the feed intake to resist the influence of tannin acid. Though tannin acid decreased their fat accumulation, voles could keep the stabilization of their body weight by regulation the balance of energy. Tannin acid could inhabit the expression of pp-MCH and its receptor in both of male and female voles.But the effect of tannin acid on the expression of pp-Orexin and its receptor was not so simple and their expression was sex difference. All of these suggested that tannin acid can influence the appetite and feeding behavior by regulation the expression of some related peptides of feeding centre of hypothalamus. |
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