Serotonergic mediation of the antidepressant-like effect of the green leaves odor in mice

doi:10.1016/j.neulet.2008.03.013

Neuroscience Letters

Volume 436, Issue 2, 9 May 2008, Pages 167-170

https://doi.org/10.1016/j.neulet.2008.03.013 Get rights and content

Abstract

The green odor (GO) that emanates from green leaves has been observed to have many physiological actions in mammals and may be associated with a healing effect in humans. This study examined the effect of GO (we used a mixture of cis-3-hexenol and trans-2-hexenal) on behavior in the forced swim test (FST) of depression in mice. Exposure of GO showed the antidepressant-like effect in the FST, i.e., a significant decrease in immobility time and increase in swimming time, but no change in climbing time. The behavioral responses of GO-exposed animals to FST were similar to those observed for animals given citalopram, which is a selective serotonin reuptake inhibitor. In contrast, desipramine, which is a selective noradrenaline reuptake inhibitor, decreased immobility time and increased climbing time without affecting swimming time. To examine the involvement of the serotonergic system in mediating the antidepressant-like action of GO, we performed further FST examinations in which GO-exposed mice were treated with p-chlorophenylalanine (PCPA). Prior PCPA administration induced depletion of central 5-HT in the brain and completely diminished the GO effect on the behavioral responses seen during the FST. No changes in locomotor activity after GO inhalation were observed. These results indicate that acute exposure to GO has an antidepressant-like effect that may involve the serotonergic system.

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Citation Excerpt :
This chronic PCPA administration schedule decreased rat brain serotonin levels by about 83.5% [13]. GO comprised equal amounts of cis-3-hexenol (Wako Pure Chemical Industries) and trans-2-hexenal (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) diluted with distilled water to 0.03% (v/v) [8,9,11]. Distilled water was used as a control odor.
Several green leaf volatiles have anxiolytic/antidepressant properties and attenuate adrenocortical stress response in rodents. However, it remains unknown whether a mixture of cis-3-hexenol and trans-2-hexenal so-called ‘green odor (GO)’ affects fear-associated post-traumatic stress disorder (PTSD)-like behavior. In the present study, fear memory of the initial conditioning stimulus was stably maintained by weekly presentation of conditioned tone. Examination of open field behavior, acoustic startle response, prepulse inhibition, and immobility in the forced swim test for 2 weeks after initial conditioning revealed that conditioned rats sustained anxiety, enhanced startle response, hypervigilance, depression-like behavior, and hypocortisolism, which is consistent with PTSD symptoms. Daily, not acute, GO presentation facilitated fear extinction and reduced PTSD-like behavioral and endocrinal responses. To further investigate the mechanism of effect of GO, we examined the effect of paroxetine (a selective serotonin reuptake inhibitor), p-chlorophenylalanine (PCPA, an irreversible serotonin synthesis inhibitor), alone or in combination of GO on PTSD-like phenotype. The alleviative effects of GO were masked by simultaneous paroxetine administration. PCPA-induced serotonin depletion abolished the effects of GO. Our results suggest that daily GO presentation facilitates fear extinction and prevents development of PTSD-like symptoms.
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Serotonergic mediation of the antidepressant-like effect of the green leaves odor in mice

Abstract

Physiol. Behav.

Physiol. Behav.

Eur. J. Pharmacol.

J. Pharm. Sci.

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Pharmacol. Biochem. Behav.

Physiol. Behav.

Pharmacol. Biochem. Behav.

Behav. Brain Res.

Genotype- and experience-dependent susceptibility to depressive-like responses in the forced-swimming test

Psychopharmacology (Berl)

Potentiation of GABAA receptors expressed in Xenopus oocytes by perfume and phytoncid

Biosci. Biotechnol. Biochem.

Antidepressant-like behavioral effects mediated by 5-hydroxytryptamine(2C) receptors

J. Pharmacol. Exp. Ther.