Abstract
BackgroundPsychological stressors may cause affective disorders, such as depression and anxiety, by altering expressions of corticotropin releasing factor (CRF), serotonin (5-HT), and tyrosine hydroxylase (TH) in the brain. This study investigated the effects of essential oil from Asarum heterotropoides (EOAH) on depression-like behaviors and brain expressions of CRF, 5-HT, and TH in mice challenged with stress.MethodsMale ICR mice received fragrance inhalation of EOAH (0.25, 0.5, 1.0, and 2.0 g) for 3 h in the special cage capped with a filter paper before start of the forced swimming test (FST) and tail suspension test (TST). The duration of immobility was measured for the determination of depression-like behavior in the FST and TST. The selective serotonin reuptake inhibitor fluoxetine as positive control was administered at a dose of 15 mg/kg (i.p.) 30 min before start of behavioral testing. Immunoreactivities of CRF, 5-HT, and TH in the brain were also measured using separate groups of mice subjected to the FST.ResultsEOAH at higher doses (1.0 and 2.0 g) reduced immobility time in the FST and TST. In addition, EOAH at a dose of 1.0 g significantly reduced the expected increases in the expression of CRF positive neurons in the paraventricular nucleus and the expression of TH positive neurons in the locus coeruleus, and the expected decreases of the 5-HT positive neurons in the dorsal raphe nucleus.ConclusionThese results provide strong evidence that EOAH effectively inhibits depression-like behavioral responses, brain CRF and TH expression increases, and brain 5-HT expression decreases in mice challenged with stress.
Highlights
Psychological stressors may cause affective disorders, such as depression and anxiety, by altering expressions of corticotropin releasing factor (CRF), serotonin (5-HT), and tyrosine hydroxylase (TH) in the brain
CRF-immunoreactive neurons in the paraventricular nucleus The expression of CRF in the paraventricular nucleus was shown after inhalation of essential oil from Asarum heterotropoides (EOAH) (Figure 3A-D)
While the forced swimming test (FST) markedly increased the expression of CRF in the paraventricular nucleus in mice receiving inhalation of saline (p < 0.001), there was an increase in 5-HT expression in those receiving inhalation of EOAH (0.5 and 1.0 g)
Summary
Psychological stressors may cause affective disorders, such as depression and anxiety, by altering expressions of corticotropin releasing factor (CRF), serotonin (5-HT), and tyrosine hydroxylase (TH) in the brain. The neurobiological substrate for depression-like behaviors induced by stress is believed to involve corticotropinergic neurons in the paraventricular nucleus, noradrenergic neurons in the locus coeruleus, and serotonergic system in the dorsal raphe nucleus [3,4]. The involvement of these substrates is supported by the report that selective serotonin. Lavender oil inhalation decreased anxiety and depression-like behaviors of rats in an elevated plus-maze test and a FST [7]. Lavender oil inhalation is effective in reducing stress-related symptoms in nurses [8]
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