Repeated Inhalation of Peppermint Essential Oil Improves Exercise Performance in Endurance-Trained Rats

Peppermint essential oil, being natural and safe, with antioxidant and anti-inflammatory properties, has long been a research interest in relieving fatigue and improving exercise performance. However, the related studies report controversial results, and the mechanisms remain unclear. Here we found that inhalation of peppermint essential oil significantly extended the exhaustion time in rats subjected to 2-week weight-bearing swimming training. Sprague-Dawley rats were subjected to a 2-week weight-loaded forced swimming regimen. Prior to each swimming session, the rats were administered peppermint essential oil via inhalation. An exhaustive swimming test was performed at the end of the protocol. Rats treated with essential oil had significantly extended time to exhaustion compared with exercised rats without essential oil treatment. In addition, treated rats also showed reduced oxidative damage induced by endurance exercise. Notably, the rats receiving two-week essential oil inhalation while not subjected to swimming training did not show improved exercise performance. The findings demonstrate that repeated inhalation of peppermint essential oil enhances the effects of endurance training and improves exercise performance partially by preventing oxidative damage.

Olfactory Stimulation with Volatile Aroma Compounds of Basil (Ocimum basilicum L.) Essential Oil and Linalool Ameliorates White Fat Accumulation and Dyslipidemia in Chronically Stressed Rats

We explored the physiological effects of inhaling basil essential oil (BEO) and/or linalool and identified odor-active aroma compounds in BEO using gas chromatography/mass spectrometry (GC-MS) and GC-olfactometry (GC-O). Linalool was identified as the major volatile compound in BEO. Three groups of rats were administered BEO and linalool via inhalation, while rats in the control group were not. Inhalation of BEO for 20 min only reduced the total weight gain (190.67 ± 2.52 g) and increased the forced swimming time (47.33 ± 14.84 s) compared with the control group (219.67 ± 2.08 g, 8.33 ± 5.13 s). Inhalation of BEO for 5 min (392 ± 21 beats/min) only reduced the pulse compared with the control group (420 ± 19 beats/min). Inhalation of linalool only reduced the weight of white adipose tissue (5.75 ± 0.61 g). The levels of stress-related hormones were not significantly different among the groups. The total cholesterol and triglyceride levels decreased after inhalation of BEO for 20 min (by more than -10% and -15%, respectively). Low-density lipoprotein cholesterol levels were lowered (by more than -10%) by the inhalation of BEO and linalool, regardless of the inhalation time. In particular, BEO inhalation for 20 min was associated with the lowest level of low-density lipoprotein cholesterol (53.94 ± 2.72 mg/dL). High-density lipoprotein cholesterol levels increased after inhalation of BEO (by more than +15%). The atherogenic index and cardiac risk factors were suppressed by BEO inhalation. Animals exposed to BEO and linalool had no significant differences in hepatotoxicity. These data suggest that the inhalation of BEO and linalool may ameliorate cardiovascular and lipid dysfunctions. These effects should be explored further for clinical applications.

l-Menthol increases extracellular dopamine and c-Fos-like immunoreactivity in the dorsal striatum, and promotes ambulatory activity in mice

Similar to psychostimulants, the peripheral administration of menthol promotes mouse motor activity, and the neurotransmitter dopamine has been suggested to be involved in this effect. The present study aimed to elucidate the effects of l-menthol on parts of the central nervous system that are involved in motor effects. The subcutaneous administration of l-menthol significantly increased the number of c-Fos-like immunoreactive nuclei in the dorsal striatum of the mice, and motor activity was promoted. It also increased the extracellular dopamine level in the dorsal striatum of the mice. These observations indicated that after subcutaneous administration, l-menthol enhances dopamine-mediated neurotransmission, and activates neuronal activity in the dorsal striatum, thereby promoting motor activity in mice.

Identification of novel target molecules of l-menthol

The present study used a binding assay to identify novel target biomolecules of l-menthol ([−]-menthol) that promote mouse ambulation. Among 88 different ligands to specific biomolecules examined, 0.1 mM l-menthol inhibited the binding of 13 ligands with relatively high inhibition rates. The assays showed that l-menthol acts on calcium channels, sodium channels, γ-aminobutyric acid type A (GABA_A) receptor, GABA transporter, dopamine transporter, dopamine D4 receptor, adenosine A2a receptor, α2A-adrenergic receptor, histamine H2 receptor, bombesin receptor, angiotensin AT1 receptor, vasopressin V2 receptor, and leukotriene B4 receptor over a similar concentration range. The inhibition constant (K_i) for l-menthol inhibition of binding of [³H]-WIN35,428 to the human recombinant dopamine transporter was 6.15 × 10⁻⁴ mol/L. The K_i for l-menthol inhibition of binding of [³H]-ethynylbicycloorthobenzoate (EBOB), a ligand of GABA_A receptor picrotoxin site, was 2.88 × 10⁻⁴ mol/L. These results should aid future research by providing clues for investigating the mechanisms underlying l-menthol activities, including the ambulation-promoting effect. The present results suggest that the dopamine transporter, adenosine A2a receptor, dopamine D4 receptor, α2A-adrenergic receptor, and GABA_A receptor are promising candidate molecules that are involved in the mechanisms underlying the psychostimulant-like effect of l-menthol.

Hyperactive behavioral phenotypes and an altered brain monoaminergic state in male offspring mice with perinatal hypothyroidism

Thyroid hormone (TH) is essential for normal brain development. TH insufficiency during early stages of development may increase the risk for attention deficit/hyperactivity disorder, in which malfunction of brain monoaminergic systems is likely involved. However, little is known about the effects of perinatal hypothyroidism on behaviors and brain monoaminergic systems in offspring mice. The present study examined in mice (1) whether perinatal hypothyroidism causes hyperactive behavioral phenotypes, (2) how perinatal hypothyroidism influences brain monoaminergic systems, and (3) whether hyperactive behavioral phenotypes are associated with the state of brain monoaminergic systems. When dams were exposed to propylthiouracil, offspring mice developed hypothyroidism during the perinatal period. Offspring mice with perinatal hypothyroidism exhibited hyperactive behavioral phenotypes such as hyper-ambulatory activity and an increased response rate in the two-way active avoidance test in a male-specific manner. Significant decreases in dopamine (DA) and serotonin turnover were observed in the striatum (ST), nucleus accumbens, hypothalamus, and hippocampus in male mice with perinatal hypothyroidism. A significant correlation between ambulatory activity and DA turnover in the ST and an augmented ambulatory response to the DA reuptake inhibitor bupropion suggested that DA in the ST was involved in the hyper-ambulatory activity in mice with perinatal hypothyroidism.

Volatile Terpenes and Brain Function: Investigation of the Cognitive and Mood Effects of Mentha × Piperita L. Essential Oil with In Vitro Properties Relevant to Central Nervous System Function

Background: Extracts of several members of the monoterpene-rich Lamiaceae sub-family Nepetoideae, including those from the Salvia (sage), Melissa (Lemon balm) and Rosmarinus (rosemary) genera, evince cognitive and mood effects in humans that are potentially related to their effects on cholinergic and GABAergic neurotransmission. To date, despite promising in vitro properties, the cognitive and mood effects of the closely related Mentha spicata (spearmint) and Mentha piperita (peppermint) remain unexplored. This study therefore assessed the human cognitive/mood effects of the M. spicata/piperita essential oil with the most promising, brain-relevant in vitro properties according to pre-trial in vitro screening. Design: Organic spearmint and peppermint (Mentha spicata/piperita) essential oils were pre-screened for neurotransmitter receptor binding and acetylcholinesterase (AChE) inhibition. In a double-blind, placebo-controlled, balanced cross-over study, 24 participants (mean age 25.2 years) consumed single doses of encapsulated placebo and 50 µL and 100 µL of the most promising essential oil (peppermint with nicotinic/GABAA receptor binding and AChE inhibitory properties, that increased calcium influx in a CAD cell neuronal model). Psychological functioning was assessed with mood scales and a range of standardised, cognitively demanding tasks pre-dose and at 1, 3 and 6 h post-dose. Results: The highest (100 µL) dose of essential oil improved performance on the cognitively demanding Rapid Visual Information Processing task (RVIP) at 1 h and 3 h post-dose and both doses attenuated fatigue and improved performance of the Serial 3 s subtraction task at 3 h post-dose. Conclusion: Peppermint (Mentha piperita) essential oil with high levels of menthol/menthone and characteristic in vitro cholinergic inhibitory, calcium regulatory and GABA_A/nicotinic receptor binding properties, beneficially modulated performance on demanding cognitive tasks and attenuated the increase in mental fatigue associated with extended cognitive task performance in healthy adults. Future investigations should consider investigating higher doses.

Behavioral effects of Citrus limon and Punica granatum combinations in rats

Dietary supplements are becoming more influential as viable treatment for common chronic diseases and to promote normal development and functions of all system including brain. Disorders like anxiety and depression may be managed through healthier variations is dietary pattern, since there are indications that diet rich in antioxidants and vitamins diminish anxiety and depression. Hence this investigation was planned to assess the behavioral effects of Citrus limon and Punica granatum in two combination doses i.e. 0.4 + 5 ml/kg and 0.2 + 8 ml/kg C. limon and P. granatum respectively in rats. Antidepressant and anxiolytic effects were explicitly judged twice during 15 days using forced swimming and open field tests and elevated plus maze. In open field test C. limon and P. granatum showed increase in distance travelled, number of central entries and number of rearing's at 0.4 + 5 ml/kg combination, in the elevated plus maze, number of open arm entries were found to be augmented and in forced swimming test, there was decline in duration of immobility and rise in duration of climbing at both combinations i.e. 0.4 + 5 ml/kg and 0.2 + 8 ml/kg C. limon and P. granatum. These results suggest that C. limon and P. granatum at 0.4 + 5 ml/kg combination have anxiolytic and antidepressant effect.

Brain regions and monoaminergic neurotransmitters that are involved in mouse ambulatory activity promoted by bupropion

Bupropion (BUP), a substituted phenyl-ethylamine, has been utilized for the treatment of depression and for smoking cessation, however, one concern is that BUP may increase a risk of psychosis similar to other substituted phenyl-ethylamine amphetamine (AMPH) and methamphetamine (MetAMPH). BUP promotes ambulation in mice and causes behavioral sensitization on the ambulation-promoting effect when repeatedly administered as well as AMPH and MetAMPH. The present study aimed to elucidate brain regions and monoaminergic neurotransmitters that are involved in the ambulation-promoting effect of BUP. c-Fos-like immunoreactivity (c-Fos-IR) mapping in brain in combination with measuring ambulatory activity was conducted to determine brain region(s) that is involved in the ambulatory effect of BUP. Three kinds of statistical analyses for c-Fos-IR in 24 brain regions consistently showed that c-Fos-IR in the Caudate putamen (CPu) is positively correlated with the ambulatory response to BUP. In addition, multiple regression analysis indicated that the ambulatory response is a function of c-Fos-IR not only in the CPu but also in the lateral septum nucleus (LS), median raphe nucleus (MnR), lateral globus pallidus (LGP), medial globus pallidus (MGP), locus coeruleus (LC) and ventral hypothalamic nucleus (VMH). Effects of BUP on monoaminergic neurotransmitters in the CPu were examined using in vivo microdialysis method, as the pharmacological experiments indicated that monoaminergic neurotransmitters, dopamine (DA) in particular, mediate the ambulatory response to BUP. Response of DA in the CPu to BUP was parallel to the ambulatory response, showing that DA in the CPu is involved in the ambulatory response to BUP. The present study also suggests that other brain regions such as the LC, the origin nucleus of norepinephrine (NE) neurons, and another neurotransmitter NE may also play some roles for the ambulatory response to BUP, however, further studies are needed to elucidate the roles.

Toxic effects of sub-chronic exposure of male albino rats to emamectin benzoate and possible ameliorative role of Foeniculum vulgare essential oil

Emamectin benzoate (EB) is an avermectin insecticide used extensively in pest control on vegetable and field crops. Few studies have been done for evaluating adverse effects of EB. In the current study, we evaluated the toxic effects of EB on male rats and the possible ameliorative role of fennel essential oil (FEO). Thirty two male rats were randomly divided into 4 equal groups. All groups were treated orally with distilled water (control group), 0.5mlFEOkg(-1) BW (FEO group), 2.5mgEBkg(-1) BW (EB group), and 0.5mlFEOkg(-1) BW+2.5mgEBkg(-1) BW (FEO+EB group) for 28 days. The obtained results showed that EB treatment resulted in a significant decrease in body weight, body weight gain, RBC count, Hb concentration, % PCV, MCV and MCHC. Moreover, EB significantly decreased total leukocyte, lymphocyte, monocyte and platelet count but significantly increased granulocyte count. EB markedly decreased total protein, albumin, globulin, IgG and IgM concentrations with a significant increase in TNF-α secretion. EB had a negative impact on the liver as it significantly increased ALT, ALP, and MDA, while decreasing SOD activity. Regarding to the histopathological examination, EB treatment induced coagulative necrosis and blood vessels congestion of the liver in treated rats. Furthermore, it resulted in depletion and necrosis of the white pulp of the spleen in treated rats. The co-administration of FEO with EB, however, improved the majority of parameters studied, suggesting that FEO is an important substance in decreasing toxic effects of EB.