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PubMed1994

Menthol-beta-D-glucuronide: a potential prodrug for treatment of the irritable bowel syndrome.

Menthol-beta-D-glucuronide is a potential prodrug for colonic delivery of the spasmolytic agent menthol. Menthol is the primary constituent of peppermint oil, which is used to treat the irritable bowel syndrome. The chemical stability of menthol-beta-D-glucuronide was assessed at various pHs (1.5, 4.5, 6.0 and 7.4) over a 4 to 24 h period at 37 degrees C. The prodrug was stable, i.e., there was less than 0.1% hydrolysis of the prodrug, at pHs of 4.5, 6.0 and 7.4. At pH 1.5, the prodrug was about 20% hydrolyzed over a 4 h period suggesting the need for an enteric coating to prevent premature hydrolysis in the stomach. The stability of the prodrug was also assessed in luminal contents of the laboratory rat and in human stool samples. These studies were performed at concentrations designed to assess relative velocities of hydrolysis (i.e., substrate concentrations in excess of the Km). The prodrug was stable in luminal contents of the rat stomach, proximal small intestine, and the distal small intestine. The rate of hydrolysis of menthol-beta-D-glucuronide was 6.26 +/- 2.88 nmol min-1 mg-1 and 2.34 +/- 1.22 nmol min-1 mg-1 in luminal contents of the rat cecum and colon, respectively. The hydrolysis rate of menthol-beta-D-glucuronide was lower in human stool samples (0.52 +/- 0.46 nmol min-1 mg-1). The prodrug had a measured log octanol/buffer partition coefficient of -1.61 suggesting it should be poorly absorbed from the lumen of the gastrointestinal tract. The data support the hypothesis that menthol-beta-D-glucuronide is a candidate for the delivery of menthol to the large intestine under in vivo conditions.

Animals↗
PubMed2006

TRPM8-independent menthol-induced Ca2+ release from endoplasmic reticulum and Golgi.

Menthol, a secondary alcohol produced by the peppermint herb, Mentha piperita, is widely used in the food and pharmaceutical industries as a cooling/soothing compound and odorant. It induces Ca2+ influx in a subset of sensory neurons from dorsal root and trigeminal ganglia, due to activation of TRPM8, a Ca2+-permeable, cold-activated member of the TRP superfamily of cation channels. Menthol also induces Ca2+ release from intracellular stores in several TRPM8-expressing cell types, which has led to the suggestion that TRPM8 can function as an intracellular Ca2+-release channel. Here we show that menthol induces Ca2+ release from intracellular stores in four widely used cell lines (HEK293, lymph node carcinoma of the prostate (LNCaP), Chinese hamster ovary (CHO), and COS), and provide several lines of evidence indicating that this release pathway is TRPM8-independent: 1) menthol-induced Ca2+ release was potentiated at higher temperatures, which contrasts to the cold activation of TRPM8; 2) overexpression of TRPM8 did not enhance the menthol-induced Ca2+) release; 3) menthol-induced Ca2+ release was mimicked by geraniol and linalool, which are structurally related to menthol, but not by the more potent TRPM8 agonists icilin or eucalyptol; and 4) TRPM8 expression in HEK293 cells was undetectable at the protein and mRNA levels. Moreover, using a novel TRPM8-specific antibody we demonstrate that both heterologously expressed TRPM8 (in HEK293 cells) and endogenous TRPM8 (in LNCaP cells) are mainly localized in the plasma membrane, which contrast to previous localization studies using commercial anti-TRPM8 antibodies. Finally, aequorin-based measurements demonstrate that the TRPM8-independent menthol-induced Ca2+ release originates from both endoplasmic reticulum and Golgi compartments.

Animals↗
PubMed1986

Effect of menthol on cold receptor activity. Analysis of receptor processes.

The effect of menthol on the discharge pattern of feline nasal and lingual cold receptors was analyzed in order to elucidate the underlying sensory transducer mechanism. A repetitive beating activity and burst (grouped) discharges were observed in both cold receptor populations at constant temperatures and after rapid cooling. An analysis of the impulse activity revealed a cyclic pattern of impulse generation, which suggested the existence of an underlying receptor potential oscillation that initiates impulses in the afferent nerve when it exceeds a threshold value. The frequency and amplitude of the periodic impulse-inducing receptor processes were characterized by the burst frequency, which increased with warming, and by the average number of impulses generated during each cycle, which increased with cooling. Menthol at micromolar concentrations induced an acceleration of the burst frequency at higher temperatures, but reduced the burst frequency in the midtemperature range. At temperatures above 25 degrees C, menthol increased the number of impulses elicited during each cycle and induced bursting in previously repetitively discharging fibers. At low temperatures, menthol suppressed bursting and finally inhibited all cold receptor activity. The impulse pattern at constant temperatures and during the dynamic response to rapid cooling was comparably affected by menthol. Calcium application completely abolished the stimulating menthol effect. Since, in equal concentrations, menthol specifically impairs neuronal calcium currents, the results are consistent with the conjecture that in cold receptors, menthol reduces the activation of a calcium-stimulated outward current by an impeding effect on a calcium conductance, thereby inducing depolarization and a modification of bursting behavior. The data confirm the hypothesis of a calcium-controlled outward conductance being involved in the generation of cyclic afferent activity in cold receptors.

Animals↗
PubMed2004

Mentholated cigarette smoking inhibits nicotine metabolism.

Smoking mentholated cigarettes has been suggested to convey a greater cancer risk compared with smoking nonmentholated cigarettes. Two of the possible mechanisms by which mentholated cigarette smoking could increase risk are by increasing systemic exposure to tobacco smoke toxins and by affecting the metabolism of nicotine or tobacco smoke carcinogens. To examine these possibilities, we performed a crossover study in 14 healthy smokers, one-half of whom were African-Americans and one-half whites. Subjects were randomly assigned to smoke mentholated or nonmentholated cigarettes for 1 week, then to cross over to the other type of cigarettes for another week. Subjects were confined to a Clinical Research Center for 3 days of each week, during which time blood levels of nicotine and carbon monoxide were measured throughout the day and an intravenous infusion of deuterium-labeled nicotine and cotinine was administered to determine the rate and pathways of nicotine metabolism. The systemic intake of nicotine and carbon monoxide was, on average, not affected by mentholation of cigarettes. Mentholated cigarette smoking did significantly inhibit the metabolism of nicotine (clearance: 1289 versus 1431 ml/min, two sided, p = 0.02). Inhibition of nicotine metabolism occurred both by slower oxidative metabolism to cotinine and by slower glucuronide conjugation. Our data do not support the hypothesis that mentholated cigarette smoking results in a greater absorption of tobacco smoke toxins. Our finding of impaired metabolism of nicotine while mentholated cigarette smoking suggests that mentholated cigarette smoking enhances systemic nicotine exposure.

Adult↗
PubMed2002

Mentholated cigarettes and smoking habits in whites and blacks.

OBJECTIVE: To determine if cigarette mentholation is associated with the frequency of smoking and with quitting, and whether mentholation explains racial differences in these two smoking behaviours. DESIGN: Cross sectional analysis of case-control data on smoking and lung cancer. SUBJECTS: Limited to 19 545 current and former cigarette smokers. MAIN OUTCOME MEASURES: Smoking > 20 cigarettes per day (cpd) versus < or = 20 cpd, and continued smoking versus quit smoking. RESULTS: Among blacks, the prevalence odds ratio (POR) of heavy smoking (> or = 21 cpd) associated with mentholated cigarettes versus non-mentholated cigarettes was 0.7 (95% confidence interval (CI) 0.5 to 0.9) in current smokers and 0.6 (95% CI 0.4 to 0.9) in former smokers. Among whites, the corresponding POR were 0.9 (95% CI 0.8 to 1.0) and 0.9 (95% CI 0.8 to 1.0). Blacks were less likely to have been heavy smokers than whites, but the difference was unrelated to cigarette mentholation. The POR of continued smoking versus quitting, associated with mentholated cigarettes was 1.1 (95% CI 1.0 to 1.2) for both blacks and whites. CONCLUSION: Smoking > 20 cpd was independently associated with white race. Among blacks, smoking < or = 20 cpd was independently associated with mentholated cigarettes. The risk of quitting was not associated with cigarette menthol flavour.

Adult↗
PubMed1993

Influence of composition of l-menthol-ethanol-water ternary solvent system on the transdermal delivery of morphine hydrochloride.

The influence of concentration of each component in l-menthol-ethanol-water ternary solvent system (MEW system) on the skin permeation of morphine hydrochloride (MPH) was investigated in hairless rats. The cumulative amount of MPH permeated through the excised abdominal skin over 8 h (Q-8) was selected as an index of skin permeability. With changing MPH concentration over a wide range from 0.01 to 10% in a MEW system (5% l-menthol and 40% ethanol), the values of Q-8 were proportional to MPH concentration. The concentration was fixed at 1% for the following experiments. For the effect of the concentration of l-menthol at 40% ethanol, the maximum Q-8 was observed at 5% l-menthol, and no greater enhancement of Q-8 was obtained by increasing l-menthol concentration above that. In the ethanol effect at 5% l-menthol, the maximum Q-8 was observed at 45% ethanol. When 2-propanol and methanol, which are more lipophilic and hydrophilic than ethanol, respectively, were used instead of ethanol, the maximum values of Q-8 were observed at 40 and 55%. The maximum values for Q-8 were obtained in the vicinity of the solubility of l-menthol in the MEW system in all cases, suggesting that the skin permeation enhancing effect of the system is dependent on the thermodynamic activity of l-menthol.

1-Propanol↗
PubMed2005

Possible warfarin interaction with menthol cough drops.

OBJECTIVE: To report a case of possible interaction of menthol cough drops (Halls) with warfarin in a patient awaiting cardioversion. CASE SUMMARY: A 57-year-old white male awaiting cardioversion for atrial fibrillation was prescribed warfarin. His dosage was adjusted to 7 mg daily to provide stable international normalized ratio (INR) values of 2.28-2.68. Approximately one week later, his INR fell to 1.45. During a follow-up interview, the patient reported that he experienced a flu-like illness during the previous week and had been using menthol cough drops. No other potential causes for the decreased INR were found. Illness will most often elevate the INR; we therefore concluded that the cough drops were the likely cause of this reaction, and the warfarin dose was increased to 53 mg/wk. After discontinuing use of menthol cough drops, the warfarin dose was returned to the previous amount and the INR remained stabilized. DISCUSSION: An objective causality assessment suggests that the decreased INR was possibly related to the use of menthol cough drops during warfarin therapy. The active ingredient in these cough drops is menthol. Menthol has been shown to affect the pharmacokinetics of other drugs by inducing or inhibiting cytochrome P450 isoenzymes and slowing drug absorption. It is not clear whether these mechanisms played a role in this case. As of January 5, 2005 this is the first case report documenting an interaction between warfarin and cough drops containing menthol. CONCLUSIONS: This case documents a significant decrease in the INR following the use of menthol cough drops. Patients who are ill have several factors that can potentially affect their INR and should be monitored closely.

Cough↗
PubMed2004

TRPM8 activation by menthol, icilin, and cold is differentially modulated by intracellular pH.

TRPM8 is a nonselective cation channel activated by cold and the cooling compounds menthol and icilin (Peier et al., 2002). Here, we have used electrophysiology and the calcium-sensitive dye Fura-2 to study the effect of pH and interactions between temperature, pH, and the two chemical agonists menthol and icilin on TRPM8 expressed in Chinese hamster ovary cells. Menthol, icilin, and cold all evoked stimulus-dependent [Ca2+]i responses in standard physiological solutions of pH 7.3. Increasing the extracellular [H+] from pH 7.3 to approximately pH 6 abolished responses to icilin and cold stimulation but did not affect responses to menthol. Icilin concentration-response curves were significantly shifted to the right when pH was lowered from 7.3 to 6.9, whereas those with menthol were unaltered in solutions of pH 6.1. When cells were exposed to solutions in the range of pH 8.1-6.5, the temperature threshold for activation was elevated at higher pH and depressed at lower pH. Superfusing cells with a low subactivating concentration of icilin or menthol elevated the threshold for cold activation at pH 7.4, but cooling failed to evoke [Ca2+]i responses at pH 6 in the presence of either agonist. In voltage-clamp experiments in which the intracellular pH was buffered to different levels, acidification reduced the current amplitude of icilin responses and shifted the threshold for cold activation to lower values with half-maximal inhibition at pH 7.2 and pH 7.6. The results demonstrate that the activation of TRPM8 by icilin and cold, but not menthol, is modulated by intracellular pH in the physiological range. Furthermore, our data suggest that activation by icilin and cold involve a different mechanism to activation by menthol.

Animals↗
PubMed1995

Mentholated cigarette use and lung cancer.

BACKGROUND: Menthol combustion produces carcinogenic compounds such as benzo[a]pyrenes. Mentholated cigarettes are much more commonly smoked by black individuals than by white individuals. The incidence of lung cancer is much higher (60%) in black men than in white men, but it differs little by race in women. We examined the association of mentholated cigarette use with lung cancer in men and women because mentholated cigarette use could help to explain the higher incidence rate of lung cancer in black men than in white men. METHODS: The study population consisted of 11,761 members of the Northern California Kaiser Permanente Medical Care Program, Oakland (5771 men and 3990 women), aged 30 to 89 years, who underwent a multiphasic health checkup in 1979 through 1985 and reported that they were current cigarette smokers who had smoked for at least 20 years. Data were collected about current cigarette brand, duration of mentholated cigarette use, and other smoking characteristics. Follow-up for incident lung cancer cases (n = 318) was carried out through 1991. RESULTS: The relative risk of lung cancer associated with mentholation compared with nonmentholated cigarettes was 1.45 in men (95% confidence interval, 1.03 to 2.02) and it was 0.75 in women (95% confidence interval, 0.51 to 1.11), adjusted for age, race, education, number of cigarettes smoked per day, and duration of smoking. Further adjustment for tar content and self-reported smoking intensity characteristics did not substantially alter the estimate of relative risk. A graded increase in risk of lung cancer with increasing duration of mentholated cigarette use was present in men. CONCLUSION: This study suggests that there is an increased risk of lung cancer associated with mentholated cigarette use in male smokers but not in female smokers.

Adult↗
PubMed1996

Menthol and nonmenthol cigarettes and smoke exposure in black and white women.

Purposes of this investigation were to compare smoke constituent exposure (CO and nicotine boosts) and smoking topography parameters between black and white women, and between women regularly using menthol or nonmenthol cigarettes. A two-factor factorial design with a sample of 37 women stratified by race and menthol or nonmenthol cigarette use was implemented. There were significant main and interaction effects of race and menthol/nonmenthol use on CO boost. Black women had a mean CO boost of 10.1 ppm vs. 7.2 ppm for white women, while women using nonmenthol cigarettes had a higher CO boost (mean = 10.6 ppm) compared to those regularly using menthol cigarettes mean = 6.5 ppm). White menthol smokers had the lowest CO boost of all subgroups. There was a trend for black women to have higher nicotine boost than white women (21.4 ng/ml vs. 15.9 ng/ml). Black women had nonsignificantly higher puff volumes compared to white women (mean = 48.4 vs. 43.5 ml), while nonmenthol smokers had nonsignificantly higher puff volumes than menthol smokers (mean = 48.5 vs. 42.7 ml). Lower CO boost with mentholated cigarettes suggests factors beyond mentholation may affect elevated smoke constituent exposure among black women.

Adult↗
PubMed2004

Modulation of human GABAA and glycine receptor currents by menthol and related monoterpenoids.

Effects of common monoterpenoid alcohols and ketones were investigated on recombinant human gamma-aminobutyric acid A (GABAA; alpha1beta2gamma2s) and glycine (alpha1 homomers) receptors expressed in Xenopus oocytes. GABA currents were enhanced by coapplications of 10-300 microM: (+)-menthol>(-)-menthol>(-)-borneol>>(-)-menthone=camphor enantiomers>carvone enantiomers, with menthol acting stereoselectively. By contrast, thujone diastereomers inhibited GABAA receptor currents while glycine currents were only markedly potentiated by menthol. Positive modulation by (+)-menthol was explored given its pronounced effects (e.g., at 100 microM, GABA and glycine EC20 responses increased by 496+/-113% and 135+/-56%, respectively). (+)-Menthol, 100 microM, reduced EC50 values for GABA and glycine from 82.8+/-9.9 to 25.0+/-1.8 microM, and from 98.7+/-8.6 to 75.7+/-9.4 microM respectively, with negligible effects on maximal currents. This study reveals a novel neuroactive role for menthol as a stereoselective modulator of inhibitory ligand-gated channels.

Animals↗
PubMed2005

Menthol facilitates the skin analgesic effect of tetracaine gel.

The aim of this study is to observe the effect of menthol on the percutaneous penetration and skin analgesic action of tetracaine gel (T-gel). Anesthetic gels containing 4% tetracaine in carbomer vehicle with and without menthol were prepared. The menthol penetration-enhanced gel conferred significantly higher diffusion of tetracaine across full-thickness mouse skin than non-penetration-enhanced gel, in a dose-dependent manner. The inter-cellular spaces of the stratum corneum in skin treated with menthol penetration-enhanced gel became extended as compared with those in non-penetration-enhanced gel. This may suggest that menthol's action was related to the changes of the epidermis ultra structures. An enlarged inter-cellular space, per se, would allow a better passage to tetracaine. To determine the efficacy of menthol penetration-enhanced tetracaine gel in the management of pain, a double-blind, placebo-controlled, randomized controlled trial (RCT) design was used. The mean verbal pain scores (VPS) were significantly lower in volunteers treated with penetration-enhanced tetracaine gel than those in volunteers receiving non-penetration-enhanced tetracaine gel or placebo. Menthol improved the analgesic efficacy of the tetracaine 4% gel in part through enhanced percutaneous permeation.

Adult↗
PubMed2003

Continual smoking of mentholated cigarettes may mask the early warning symptoms of respiratory disease.

BACKGROUND: Continual use of cold preparations including those containing menthol for relief from congestion, cough, or difficulty in breathing can mask the early warning symptoms of respiratory dysfunction. These products usually carry a warning label on the packaging that indicates that they are not for continuous use and may mask the early warning symptoms of a more serious condition. Menthol can be delivered in many dosage forms including the smoke of a mentholated cigarette. METHODS: Literature searches were done for the NLM databases (e.g., MEDLINE from 1966, TOXLINE, OLDMEDLINE (1958-1965), CANCERLIT), plus tobacco industry documents and hardcopy indices. The evidence was evaluated with application to mentholated cigarette smoking. RESULTS: A logical progression is presented to attempt to demonstrate that the continuous smoking of mentholated cigarettes may also mask the early warning symptoms of respiratory distress. The early warning symptoms caused by chronic irritation of the respiratory tract may be reduced in severity when the menthol found in a mentholated cigarette is continually delivered to the tract. CONCLUSION: This masking of the symptoms of an underlying respiratory disease can lead to delays in seeking medical attention resulting in a poor prognosis, additional suffering, and eventual death.

Black or African American↗
PubMed2002

Menthol: a natural analgesic compound.

Menthol, after topical application, causes a feeling of coolness due to stimulation of 'cold' receptors by inhibiting Ca++ currents of neuronal membranes. Since Ca++ channel blockers are endowed with analgesic properties, the aim of the present study was to investigate the potential antinociceptive effect of menthol. (-)-Menthol produced a dose-dependent increase in the pain threshold in the mouse hot-plate (3-10 mg kg(-1) p.o.) and abdominal constriction (3-10 mg kg(-1) p.o.; 10 microg per mouse intracerebroventricularly (i.c.v.)) tests. The antinociceptive effect of (-)-menthol was antagonised by the unselective opioid antagonist naloxone and by the selective kappa-antagonist nor-NBI. Conversely, CTOP (mu-antagonist), 7-benzylidenenal-trexone (delta(1) antagonist) and naltriben (delta(2) antagonist) did not prevent (-)-menthol antinociception. In both tests, (+)-menthol (10-50 mg kg(-1) p.o.; 10-30 microg per mouse i.c.v.) was unable to modify the pain threshold. These results indicate that (-)-menthol is endowed with analgesic properties mediated through a selective activation of kappa-opioid receptors.

Acetic Acid↗
PubMed1999

Transbuccal permeation of a nucleoside analog, dideoxycytidine: effects of menthol as a permeation enhancer.

The use of a safe and effective permeation enhancer is paramount to the success of a buccal drug delivery system intended for systemic drug absorption. The enhancing effects of menthol (dissolved in an aqueous buffer in the absence of co-enhancers) on buccal permeation of a model hydrophilic nucleoside analog, dideoxycytidine (ddC), were investigated. In vitro transbuccal permeation of ddC was examined using freshly obtained porcine buccal mucosa. The experiments were carried out in side-bi-side flow through diffusion cells. Permeation enhancement studies were performed with varying concentrations of l-menthol dissolved in Krebs buffer solutions containing ddC. Partition coefficient experiments were carried out to probe into the mechanism of permeation enhancing properties of l-menthol and DSC studies were conducted to determine if there is a eutectic formation between ddC and l-menthol at various concentrations. Permeation of ddC increased significantly (P<0.05) in the presence of l-menthol independent of the concentration of the terpene. The apparent 1-octanol/buffer partition coefficient (log K(p)) of ddC was significantly (P<0.05) increased in presence of l-menthol and was also independent of the enhancer concentration. However, the tissue/buffer partition coefficient (log K'(p)) data showed a concentration dependent increase of log K'(p) in presence of l-menthol. Since log K'(p) is a measure of drug binding to the tissue in addition to drug partitioning, binding of ddC to the buccal tissue may provide an explanation for the concentration dependent increase in these values.

Animals↗
PubMed1988

The effects of D and L isomers of menthol upon nasal sensation of airflow.

Objective and subjective measurements of nasal airflow were made before and after inhalation of Vanilla, D-Menthol and L-Menthol separately. Despite the fact that the menthol isomers were mirror images of one another, only L-Menthol produced the sensation of increased nasal airway patency. No objective change in resistance was found after inhaling either D-Menthol, L-Menthol or the vanilla control. These findings demonstrate that L-Menthol exerts a specific action upon nasal sensory nerve endings, which are responsible for the subjective appreciation of nasal airflow.

Adult↗
PubMed2001

[Does the inhalation of a 1% L-menthol solution in the premedication of fiberoptic bronchoscopy affect coughing and the sensation of dyspnea?].

BACKGROUND: Inhalation of l-menthol inhibits cough and has been shown to reduce respiratory discomfort associated with loaded breathing. We investigated the effect of the inhalation of a 1% l-menthol solution in the premedication of fiberoptic bronchoscopy (FB) on the frequency of cough and the irritability of the tracheobronchial mucosa during FB in a blinded, randomized and placebo controlled study. METHODS: 64 pat. (30-78 yrs, 55 males) underwent routine FB. Premediction: atropine and hydrocodone s.c., inhalation of oxybuprocain by means of a jet nebulizer, sedation on demand. Verum-group: inhalation of 3 ml 1% l-menthol-solution. Placebo-group: 3 ml 0.05% l-menthol (to provide the typical smell). Before and after inhalation peak respiratory flow (PEF) was registered, during FB the frequency of cough was measured. The bronchoscopist scored the irritability of the tracheobronchial mucosa using a visual analog scale. The patients answered a questionnaire addressing their perception of dyspnea and cough on the day after FB compared to the day before. RESULTS: The cough counts didn't show a significant difference between the groups. The irritability of the mucosa was increased in the verum group (main bronchus verum 62.2 +/- 22, placebo 48.6 +/- 23 [mm vissual analog scale, p = 0.03]). Cough and dyspnea reported by the patients decreased on the day after FB significantly compared to the day before (no difference between the groups). The inhalation of 1% l-menthol induced a significant increase of the PEF (verum 307 +/- 103 pre, 329 +/- 84 post [l/min, p = 0.003]) compared to placebo. CONCLUSIONS: The inhalation of 1% l-menthol did not enhance the tolerability of the FB. However, l-menthol induced a significant increase of the PEF immediately after inhalation. Finally sensation of dyspnea was decreased in both groups at the day post FB.

Administration, Inhalation↗
PubMed2000

l-Menthol-induced [Ca2+]i increase and impulses in cultured sensory neurons.

We investigated the effects of l-menthol on cultured dorsal root ganglion (DRG) cells, instead of free nerve endings of sensory fibers. Using Fura-2 microfluorimetry, we identified a few DRG neurons that showed an increase in intracellular free Ca2+ concentration ([Ca2+]i) in response to l-menthol. They made up only 10% of the neurons activated by a high K+ solution. l-Menthol induced the [Ca2+]i increase in a dose-dependent manner, with an EC50 of 37.9 microM and a Hill coefficient of 0.97. A related compound, cyclohexanol, had no effect. When extracellular Ca2+ was removed, l-menthol did not induce the [Ca2+]i increase. Whole-cell current-clamp recordings revealed that l-menthol induced depolarization (13.2 mV, receptor potential) leading to impulses. We conclude that l-menthol induced the impulses through activation of menthol receptors in a small subset of the cultured sensory neurons.

Animals↗