The Influences of Chrysin on Stress-Induced Changes of Melanin-Concentrating Hormone and Orexin Gene Expression in Rats

Chrysin is a bioactive component of herbal medicines such as Passiflora incarnate, Passiflora caerulea, and Oroxylum indicum. Although evidence has demonstrated the neuroprotective, anti-inflammatory, and pain-relieving effects of chrysin, the intra-hypothalamic molecular mechanisms underlying the anxiolytic effects of chrysin are still unclear. This study aimed to explore the effects of chrysin on hypothalamic orexin and melanin-concentrating hormone (MCH) gene expression in a rat model of stress.

Twenty male Wistar rats (200 ± 10 g) were segregated into four groups (n = 5). For the induction of stress, the animals were placed in the restraint cage for 2 hours. The intact and stressed groups received saline. Thirty minutes before the induction of stress, chrysin was injected into the other two groups of the stress model at a dosage of 20 or 40 μg via the third cerebral ventricle. Hypothalamic samples were removed and frozen, and the relative gene expression of orexin and MCH was measured using the real-time polymerase chain reaction technique.

The induction of stress significantly increased mRNA levels of orexin and MCH compared to the control rats. The mRNA levels of MCH and orexin significantly declined in rats receiving chrysin compared to the stress group.

The inhibition of the hypothalamic MCH and orexin neuronal circuits may be involved in the preventive effects of chrysin against stressful situations. Chrysin may be a potential target to manage anxiogenic behaviors due to the down-regulation of MCH and orexin gene expression upstream the hypothalamic corticotropin-releasing hormone.