Behavioural and neurochemical effects after repeated administration of N-ethylpentylone (ephylone) in mice.

N-ethyl-pentylone (NEP), also known as 'ephylone' and N-ethylnorpentylone, has been identified as one of the most recent novel psychostimulants to emerge into the illicit drug market and it has been associated with some intoxications and even fatalities. However, little is known about the consequences of its repeated consumption as well as the role of the monoaminergic system in such consequences. Thus, the aim of our study was to investigate the neurochemical profile and the behavioural effects after both acute and repeated NEP exposure. Male OF1 mice were acutely (1, 3, 10 mg/kg, i.p.) or repeatedly (1, 3, 10 mg/kg, i.p., 5 days, twice/day) exposed to NEP, and anxiety-like behaviour, aggressiveness, social interaction, depressive-like symptoms, body temperature, changes in monoaminergic enzymes and neurotransmitters levels as well as ΔFosB in striatum and prefrontal cortex (PFC) from post-mortem tissue were analysed short after drug-exposure or during drug-withdrawal. Acute administration of NEP induced anxiolytic effects but also an aggressive behaviour and social exploration deficits in mice, which persist during NEP-withdrawal. Moreover, NEP induced hyperthermia as well as depressive-like symptoms after repeated administrations that may be related to the decrease in serotonin and noradrenaline levels observed in striatum and PFC. Finally, the long-term increase in ΔFosB levels in striatum after NEP chronic exposure points to a high risk of dependence. Altogether indicates that NEP consumption induces different neurological and neuropsychiatric disorders accompanied by changes in the monoaminergic system, posing a threat to public health.

Bioisosteric Modification of To042: Synthesis and Evaluation of Promising Use-Dependent Inhibitors of Voltage-Gated Sodium Channels.

Three analogues of To042, a tocainide-related lead compound recently reported for the treatment of myotonia, were synthesized and evaluated in vitro as skeletal muscle sodium channel blockers possibly endowed with enhanced use-dependent behavior. Patch-clamp experiments on hNav1.4 expressed in HEK293 cells showed that N-[(naphthalen-1-yl)methyl]-4-[(2,6-dimethyl)phenoxy]butan-2-amine, the aryloxyalkyl bioisostere of To042, exerted a higher use-dependent block than To042 thus being able to preferentially block the channels in over-excited membranes while preserving healthy tissue function. It also showed the lowest active transport across BBB according to the results of P-glycoprotein (P-gp) interacting activity evaluation and the highest cytoprotective effect on HeLa cells. Quantum mechanical calculations and dockings gave insights on the most probable conformation of the aryloxyalkyl bioisostere of To042 in solution and the target residues involved in the binding, respectively. Both approaches indicated the conformations that might be adopted in both the unbound and bound state of the ligand. Overall, N-[(naphthalen-1-yl)methyl]-4-[(2,6-dimethyl)phenoxy]butan-2-amine exhibits an interesting toxico-pharmacological profile and deserves further investigation.

Acute exposure to N-Ethylpentylone induces developmental toxicity and dopaminergic receptor-regulated aberrances in zebrafish larvae.

N-Ethylpentylone (NEP) is one of the most recent novel stimulants, and there is limited understanding of its toxicity. Here we employed zebrafish model for analyzing the effects of NEP on early embryos and cardiovascular and nervous systems at late developmental stages. We first observed multi-malformations in early embryos and larvae after NEP administration, together with significant deregulations of brain and heart development-associated genes (neurog1, her6, elavl3, nkx2.5, nppa, nppb, tnnt2a) at transcriptional level. Low-dosed NEP treatment induced an anxiety-like phenotype in zebrafish larvae, while higher doses of NEP exerted an inhibitory effect on locomotion and heart rate. Besides, the expression of th (tyrosine hydroxylase) and th2 (tyrosine hydroxylase 2), identifying dopamine (DA) release, were significantly increased during one-hour free swimming after effective low-dosed NEP administration, along with the upregulation of gene fosab and fosb related to stress and anxiety response. D1R antagonist SCH23390 and D2R antagonist sulpiride partially alleviated the aberrances of locomotion and heart rate, indicating dopaminergic receptors were involved in the bidirectional dosage-dependent pattern of NEP-induced performance. Meanwhile, sulpiride offset the upregulated expression of th, th2 and fosab in the group of 1.5 µM NEP, which highlighted the significant role of D2R in NEP-induced locomotive effects. This study systematically described the developmental, neuronal and cardiac toxicity of NEP in zebrafish, and identified the dopaminergic receptors as one of the downstream effectors of NEP administration.

Analytical quantification, intoxication case series, and pharmacological mechanism of action for N-ethylnorpentylone (N-ethylpentylone or ephylone).

Synthetic cathinones continue to proliferate in clandestine drug markets worldwide. N-ethylnorpentylone (also known as N-ethylpentylone or ephylone) is a popular emergent cathinone, yet little information is available about its toxicology and pharmacology. Here we characterize the analytical quantification, clinical presentation, and pharmacological mechanism of action for N-ethylnorpentylone. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to quantify N-ethylnorpentylone in blood obtained from human cases. Clinical features exhibited by the intoxicated individuals are described. The activity of N-ethylnorpentylone at plasma membrane transporters for dopamine (DAT), norepinephrine (NET) and 5-HT (SERT) was assessed using in vitro assays measuring uptake inhibition and evoked release of [3 H] neurotransmitters in rat brain synaptosomes. Our LC-MS/MS method assayed N-ethylnorpentylone concentrations with limits of detection and quantification of 1 and 5 ng/mL, respectively. Quantitation was linear from 5 to 500 ng/mL, and the method displayed specificity and reproducibility. Circulating concentrations of N-ethylnorpentylone ranged from 7 to 170 ng/mL in clinical cases, and the associated symptoms included palpitations, tachycardia, agitation, hallucinations, coma and death. N-Ethylnorpentylone was a potent inhibitor at DAT (IC50  = 37 nM), NET (IC50  = 105 nM) and SERT (IC50  = 383 nM) but displayed no transporter releasing activity. We present a validated method for quantifying N-ethylnorpentylone in human case work. The drug is a psychomotor stimulant capable of inducing serious cardiovascular and neurological side-effects which can be fatal. In vitro findings indicate that N-ethylnorpentylone exerts its effects by potent blockade of DAT and NET, thereby elevating extracellular levels of dopamine and norepinephrine in the brain and periphery.

The Antitussive Benzonatate Is Not Tumorigenic in Rodent Carcinogenicity Studies.

Benzonatate is a peripheral oral antitussive that dampens the activity of cough stretch receptors. Rodent carcinogenicity studies were performed in Tg.rasH2 mice and Wistar Han rats. Mice were orally gavaged benzonatate at 10, 30, 75, and 100 mg/kg/day for males and 5, 15, and 50 mg/kg/day for females. Rats were gavaged at 10, 30, and 90 mg/kg/day for males and 5, 15, and 50 mg/kg/day for females. Higher doses in males were due to differences in maximum tolerated doses in dose-ranging studies. In both species, benzonatate was not detected in plasma because of rapid ester hydrolysis producing 4-(butylamino) benzoic acid (BBA) and methylated polyethylene glycol polymer. This metabolism was similar in human plasma; therefore, plasma BBA was used to show systemic exposure. Both species had no evidence of a benzonatate-related increase in any neoplasm. A slight increase in nasal cavity exudative inflammation was present in benzonatate-dosed male mice. Retinal atrophy was observed in male rats at ≥30 mg/kg/day, but the incidence was within historical control data range and not related to benzonatate. In conclusion, benzonatate and its 2 major metabolites were not carcinogenic in rodent carcinogenicity studies at BBA exposures of ≥32 and 70 times a 200 mg human benzonatate dose, respectively.

Genotoxicity assessment of the novel antitussive agent Benzonatate and its major metabolite.

Benzonatate (TESSALON®) is a peripherally acting oral antitussive. It undergoes rapid ester hydrolysis producing 4-(butylamino) benzoic acid (BBA) and methylated polyethylene glycol (MPG) metabolites, which are eliminated in urine and feces. The nonclinical and clinical efficacy of Benzonatate has been demonstrated over the last 60 years, but its safety was not fully assessed. In this study, we tested the genotoxicity of Benzonatate and its major metabolite BBA in an in vitro bacterial reverse mutation and in vivo micronucleus assays. A chromosomal aberration assay was also performed on Benzonatate and BBA. In the reverse mutation assay, Benzonatate and BBA doses 1.5-5000 µg/plate ±â€¯S9 metabolic activation were used and the numbers of revertants/plate were compared to various controls. Chromosomal aberration assays with human peripheral blood lymphocytes used Benzonatate and BBA concentrations 25-2000 and 62.5-1930 µg/mL, respectively. A CByB6F1 mouse bone marrow micronucleus assay was performed as part of a 28-day oral toxicology study at up to 250 mg/kg/day. The frequencies of micronuclei in polychromatic erythrocytes in treated groups were compared with the control group. Neither Benzonatate nor BBA induced significant mutagenicity in any of the bacterial strains, with or without metabolic activation. They also did not produce any biologically relevant structural or numerical aberrations in human chromosomes. Benzonatate and its BBA and MPG metabolites rapidly produced from esterase activity did not produce any significant increase in the incidence of micronucleated polychromatic erythrocytes. In conclusion, Benzonatate and its major metabolite BBA were not mutagenic and did not cause numerical or structural chromosome alterations. While the MPG metabolite was not tested, studies on structural analogues indicated it was also unlikely to be genotoxic. This was supported by oral rodent carcinogenicity assays showing no increase in malignancies.

Clinical Presentation, Autopsy Results and Toxicology Findings in an Acute N-Ethylpentylone Fatality.

The clinical presentation, autopsy findings and toxicology results in an acute fatality involving N-ethylpentylone, a new cathinone derivative, are described. Law enforcement transported a male who was agitated and exhibiting unusual behavior to a local hospital. Upon arrival at the hospital, his body temperature was 105.5 degrees Fahrenheit and his blood pH was 6.7. Clinical laboratory analysis revealed elevated troponins, rhabdomyolysis, hypoglycemia, hepatic and renal injury, respiratory failure and disseminated intravascular coagulation. He was intubated and admitted to the intensive care unit, treated with cooling blankets, bicarbonate and intravenous fluids. Despite medical treatment, he went into cardiac arrest and was pronounced dead ~36 h after admission. Autopsy findings identified some abrasions on his arms and legs, a bloody nose and a mildly enlarged heart. Antemortem blood was analyzed by gas chromatography coupled with a mass spectrometer which identified N-ethylpentylone. Based on clinical presentation, autopsy findings and toxicology results, the medical examiner concluded the cause of death was intoxication by N-ethylpentylone and the manner of death was accident.

Medical management of a potentially toxic accidental trialkylamine ingestion during spaceflight.

INTRODUCTION: To reduce excessive iodine consumption by astronauts, the National Aeronautics and Space Administration (NASA) has developed various methods of removing residual iodine after iodine-based water purification aboard spacecraft. The Low Iodine Residual System (LIRS) was developed as an iodine removal system for use aboard the space shuttle. This is a case report of an accidental, potentially toxic ingestion by astronauts aboard a space shuttle mission following exposure to contaminated water from LIRS filtration and the medical response operations that followed. CASE REPORT: Astronauts ingested significant levels of trialkylamines from water that had passed through gamma-irradiated, de-iodination resin in the LIRS hardware. Medical response operations included crew evaluations, consultations with toxicologists and systems experts, hardware testing, contaminant evaluation, and close crewmember follow-up. DISCUSSION: Despite the significant ingestion there were no adverse clinical symptoms in any of the exposed astronauts; however, the case highlights a simple pitfall in the classification of hardware that ultimately lead to a potentially harmful toxic ingestion among the crewmembers, and the real-time response of medical personnel to ensure crew safety.

Evaluating the role of curcum powder as a protective factor against bladder cancer--an experimental study.

Throughout human history, plant products have been used for many purposes including as medicines. Herbal products and spices can be used as preventive agents against cancer due to their antimicrobial, antioxidant and antitumorigenic properties. This study was designed to evaluate the potential protective effect of curcum in rats administered nitrosamine precursors; dibutylamine (DBA) and sodium nitrate (NaNO3); and infected with Escherichia coli (E. coli) and also to monitor changes in nuclear factor the Kappa B p65 (NF-κB p56) pathway and its downstream products, Bcl-2 and interleukin-6 (IL-6), in parallel with nitrosamine precursors, E. coli and curcum treatment. Rats were divided into three groups (n=25 each; except of control group, n+20). Group I a normal control group, group II administered DBA/NaNO3 in drinking water and infected with E. coli and group III was administered DBA/NaNO3 in drinking water, infected with E. coli and receiving standard diet containing 1% curcum powder. Histopathological examination reflected that the curcum treated group featured a lower incidence of urinary bladder lesions,and lower levels of NF-κB, Bcl-2 and IL-6, than the group receiving nitrosamine precursor and infected with E. coli. These findings suggested that curcum may have a protective role during the process of bladder carcinogenesis by inhibiting the NF-κB pathway and its downstream products.

Electrophilic reactions of skin-sensitizing sultones.

Reactions of the strong skin sensitizer hexadec-1-ene-1,3-sultone with sodium hydroxide, sodium methoxide, sodium metabisulfite, sodium butanethiolate, n-butylamine, and aniline have been investigated, and the reaction products have been identified. Most of the nucleophiles studied react by nucleophilic addition (Michael type addition) to the double bond at the 2-position, although in most cases the final products result from further reactions of the initital adducts. The findings are considered together with those reported by Meschkat, Barratt, and Lepoittevin for reactions of hex-1-ene-1,3-sultone and hexane-1,3-sultone, and the implications of the two sets of findings for the mechanism of skin-sensitizing action are discussed. It is concluded that nucleophilic attack at the 3-position of the alk-1-ene-1,3-sultones occurs only with those nucleophiles, which either have very low reactivity in nucleophilic addition or are unable to give rise to thermodynamically stable products via initial reaction at the 2-position. It is further concluded that the observed differences in electrophilic reactivity between alk-1-ene-1,3-sultones and alkane-1,3-sultones are not large enough to rationalize the differences in skin sensitization properties between the two types of sultone. It is suggested that the differences in specificity arise because the alk-1-ene-1,3-sultones act as Michael type electrophiles whereas the alkane sultones act as SN2 electrophiles. It is suggested that the reason for the greater potency of the alk-1-ene-1,3-sultones may be the ability of the initial C2 adducts with protein to undergo further reactions by substitution at C3, leading to cross-linking and consequent perturbation to the protein tertiary structure.

Effects of di-n-butylamine on the respiratory system of Wistar (WU) rats after subchronic inhalation.

Aim of the study was to investigate the potential toxic effects of di-n-butylamine (DBA), a known skin and eye irritating compound, on the respiratory tract after inhalation exposure for up to 91 days in male and female rats [Crl:(WI)WU BR]. To check whether and to what degree the no-observed-(adverse)-effect level (NO(A)EL) decreases with increasing study duration, serial sacrifices were performed after 3 and 28 days, respectively. Based on two dose range-finding studies, the concentrations for this study were determined with 0 (clean air), 50, 150, and 450 mg/m(3). Animals were exposed for 3 days (6 h/day) 28, and 91 days (5 days/wk, 6 h/day), respectively, and immediately sacrificed thereafter. The results show clear irritating effects only in the upper part of the respiratory tract, that is, the nasal cavities. While after 3 and 28 days effects were found only in the high-dose group, slight adaptive effects, expressed as mucous (goblet) cell hyperplasia, could be diagnosed in the medium- and low-dose groups after 91 days of exposure. Pathological changes were most prominent after 3 days of exposure. In the lung, only marginal effects could be observed (increased relative lung weight only in females of the high concentration after 28 days, slight, not statistically significant histopathological effects in the high concentration after 3 days, no effects on parameters of bronchoalveolar lavage fluid), while no effects were found in the remaining groups.

Developmental toxicity of oral n-butylamine hydrochloride and inhaled n-butylamine in rats.

Pregnant Wistar rats were administered 0, 100, 400 or 1000 mg mono-n-butylamine hydrochloride/kg body weight/day by gavage on days 6 through 15 post coitum (sperm-positive=day 0), or inhaled mono-n-butylamine 0, 17, 50 or 152 ppm (whole-body exposure), 6 h/day on days 6 through 19 post coitum. Oral n-butylamine HCl 1000 mg/kg reduced maternal feed consumption, increased early post-implantation losses (embryonic resorptions), reduced fetal and placental weight, and retarded skeletal development (incomplete skull and sternebral ossification), and produced malformations (filiform/kinked tail, enlarged cardiac ventricular chamber(s), malpositioned heart, aortic arch atresia, diaphragmatic hernia); 100 mg/kg was the no-observed-adverse effect level (NOAEL) for prenatal developmental toxicity; 400 mg/kg, the maternal no-effect level, produced only malformations (aortic arch atresia, malpositioned heart, diaphragmatic hernia). Inhaled n-butylamine produced concentration-dependent nasal epithelial hyperplasia and squamous metaplasia, inflammation and necrosis; the maternal NOAEL was less than 17 ppm. There were no treatment-related signs of embryo/fetotoxicity, particularly, no effects on fetal morphology. The developmental NOAEL was 152 ppm. The neutralization of n-butylamine by hydrochloride converts it from a strong alkali causing tissue burns into a weak acid/base which is fetotoxic. Possible mechanisms of fetotoxicity are free radical production, metabolic acidosis, and lysosomotrophy.

The relationship of clinical QT prolongation to outcome in the conscious dog using a beat-to-beat QT-RR interval assessment.

QT interval prolongation of the electrocardiogram has been associated with the occurrence of life-threatening fatal ventricular arrhythmias. To understand the relationship between preclinical cardiac conduction assessment to clinical outcome, comparisons of free (unbound)-plasma drug concentrations and their associated effects in the conscious mongrel dog were made to the free plasma concentrations in humans reported to produce QT prolongation. E-4031 (an experimental class III antiarrhythmic), cisapride, terfenadine, terodiline, and verapamil all affect cardiac repolarization and can produce QT prolongation in humans. In the conscious dog, the QT interval was assessed on a beat-to-beat basis in relation to each preceding RR interval at concentrations approximating the same unbound human concentrations. E-4031, cisapride and terodiline statistically increased the QT(RR1000) interval [the QT interval at a 60 beats/min (bpm) heart rate] 23, 8, and 9 ms, respectively, at concentrations 0.3 to 15.8 times their relevant clinical level. Increases were not observed for terfenadine or verapamil (p > 0.05 at all doses). Inspection of individual dog QT versus RR interval relationships showed clear QT interval responses specific to each treatment but not readily apparent when data are averaged at a heart rate of 60 bpm. For specific rectifier K(+) current (IKr) blockers, robust effects on mean QT prolongation can be detected. However, for drugs that affect repolarization through multiple channels, the effect on the mean QT interval may be more difficult to detect. Inspection of the beat-to-beat QT-RR interval relationship in an individual animal can increase the sensitivity for more accurate clinical prediction.

Pharmacokinetic/pharmacodynamic assessment of the effects of E4031, cisapride, terfenadine and terodiline on monophasic action potential duration in dog.

1. Torsades de pointes (TDP) is a potentially fatal ventricular tachycardia associated with increases in QT interval and monophasic action potential duration (MAPD). TDP is a side-effect that has led to withdrawal of several drugs from the market (e.g. terfenadine and terodiline). 2. The potential of compounds to cause TDP was evaluated by monitoring their effects on MAPD in dog. Four compounds known to increase QT interval and cause TDP were investigated: terfenadine, terodiline, cisapride and E4031. On the basis that only free drug in the systemic circulation will elicit a pharmacological response target, free concentrations in plasma were selected to mimic the free drug exposures in man. Infusion regimens were designed that rapidly achieved and maintained target-free concentrations of these drugs in plasma and data on the relationship between free concentration and changes in MAPD were obtained for these compounds. 3. These data indicate that the free ED50 in plasma for terfenadine (1.9 nM), terodiline (76 nM), cisapride (11 nM) and E4031 (1.9 nM) closely correlate with the free concentration in man causing QT effects. For compounds that have shown TDP in the clinic (terfenadine, terodiline, cisapride) there is little differentiation between the dog ED50 and the efficacious free plasma concentrations in man (< 10-fold) reflecting their limited safety margins. These data underline the need to maximize the therapeutic ratio with respect to TDP in potential development candidates and the importance of using free drug concentrations in pharmacokinetic/pharmacodynamic studies.

Protective role of soybean feeding against the cytogenetical and histopathological effects of dibutylamine and sodium nitrate on bone marrow and liver of mice.

The protective role of soybean feeding against the cytogenetic and histopathologic effects of the nitrosamine precursors sodium nitrate and dibutylamine was evaluated. Treated animals were killed every 3 months, over a period of 15 months, and bone marrow cells were prepared for cytogenetic studies and livers for histopathological observations. Structural chromosomal aberrations and mitotic indices increased after treatment with the nitrosamine precursors for all tested times. Livers were within the normal appearance during the first 6 months. After that a mild, moderate, marked dysplasia with lymphocytic infiltration, fatty vacuolation and liver atrophy was observed. Soybean coadministered with the nitrosamine precursors reduced the number of structural chromosomal aberrations. Mitotic indices decreased at all tested groups but still higher than the control level. A marked reduction in dysplastic features in the liver cells was observed. In conclusion, the cytogenetic and histopathologic results of this study strongly support the protective role of soybean against the genotoxic and carcinogenic action of nitrosomine formed in vivo from its precursors.

Stereoselective cardiotoxic effects of terodiline.

OBJECTIVE: To study the cardiovascular and electrocardiographic (ECG) effects of the R(+)- and S(-)- enantiomers of terodiline. The racemic drug was previously used to treat detrusor instability but was withdrawn after it caused serious ventricular arrhythmias associated with prolongation of the QT interval. METHODS: A double-blind, placebo-controlled, randomized crossover study was performed that involved nine healthy volunteers who were given single oral doses of racemic terodiline hydrochloride (200 mg), R(+)-terodiline hydrochloride (100 mg), S(-)-terodiline tartrate (100 mg), or placebo. Plasma concentrations of each enantiomer and cardiovascular and ECG effects, including QT intervals and QT dispersion, were measured over 14 days after each treatment. RESULTS: Both racemic and R(+)-terodiline significantly increased QT interval, corrected QT interval (QTc), and QRS duration (all p < 0.05), without affecting QT dispersion. S(-)-Terodiline tartrate (100 mg) did not affect QTc. Peak effects occurred 8 hours after dosing when increases in QTc from baseline (95% confidence intervals) were -3 (-20, 13) for placebo, 23 (8, 37) for racemic terodiline, 19 (6, 33) for R(+)-terodiline, and 0 (-10, 9) ms1/2 for S(-)-terodiline. Although differences were observed between the pharmacokinetics of the two enantiomers, these were not sufficient to account for the differences in ECG effects, and elimination half-lives were similar. Elimination of terodiline enantiomers was not significantly delayed in two genotypic poor metabolizers of debrisoquin (CYP2D6). CONCLUSIONS: QT prolongation associated with racemic terodiline is caused exclusively by the R(+)-enantiomer, which therefore appears to be responsible for the ventricular arrhythmias caused by the drug.

Intraduodenal absorption in the rabbit of a novel heparin salt.

The intraduodenal absorption of a new low-molecular-weight heparin (LMWH) diamine salt (ITF 1331) was compared with the parent compound ITF 1060 and with sodium LMWH, in anaesthetized rabbits. The administration of either salt, but not of sodium LMWH, resulted in a dose-related increase in plasma anti-Xa activity. In this respect ITF 1331 was slightly superior to ITF 1060, and in acute-toxicity studies the counterion itself (ITF 258) was less toxic than that in ITF 1060 (counterion No. 4). These data confirm that a tertiary diamine within the counterion is an important structural requirement for the bioavailability of heparin by the intraduodenal route, and suggest that ITF 1331 may represent an important advance in the search for an oral heparin.

The synthesis and antilipidperoxidation activity of 4,4-diarylbutylamines and 4,4-diarylbutanamides.

A series of 4,4-diarylbutylamine and 4,4-diarylbutanamide derivatives has been synthesized and evaluated for their antilipidperoxidation (ALP) activity and acute toxicity (LD50). Some of them were found to have significant ALP activity.

Structure-activity relationships of airway irritating aliphatic amines. Receptor activation mechanisms and predicted industrial exposure limits.

Sensory irritation due to inhalation of diethyl-, triethyl-, dibutyl-, tributyl- and cyclohexylamine was estimated from the decrease in respiratory rate in normal mice (American Standard Method E981-84). The concentration-effect relations followed Michaelis-Menten equations, except for diethylamine, for which a threshold was found. The concentrations depressing the respiratory rate by 50% (RD50) for diethyl-, triethyl-, dibutyl- and cyclohexylamine were 184, 186, 81 and 27 ppm, respectively. For tributylamine the maximum response was too low to achieve a RD50 value. Pulmonary irritation was estimated from the decrease in respiratory rate in tracheal-cannulated mice. The respective concentrations depressing the respiratory rate by 50% (tRD50) were 549, 691, 101, 96 and 78 ppm for diethyl-, triethyl-, dibutyl-, tributyl- and cyclohexylamine. Only minor or no effects on the tidal volumes were found at the lower exposure concentrations. The trigeminal and pulmonary receptors are believed to be activated directly by the amines, and the receptor environments are believed to be lipophilic. Structure-activity analysis was made by comparing the effects of the amines with the effects of previously investigated primary n-alkylamines. Occupational exposure limits (TLV) were estimated for both effects. Finally, the sensory irritation effect was found to be an important part of the odour sensation, also below the TLVs.

Sensory and pulmonary irritation of inhaled n-butylamine in CF-1 and NMRI mice.

Sensory and pulmonary irritation of butylamine was investigated in CF-1 and NMRI mice according to the American standard test method (ASTM E981-84). The method is based on the reflexively induced reduction of the respiratory rate of mice, when exposed to chemical irritants. Sensory irritation was investigated in normal mice, yielding RD50 values (concentration which reduces the respiratory rate by 50%) of 121 and 246 ppm for CF-1 and NMRI mice, respectively. The concentration-effect curves were parallel, but had significantly different elevations, indicating a lower sensitivity of NMRI mice. Pulmonary irritation was investigated in mice, inhaling through a tracheal cannula, yielding RD50 values of 300 and 362 ppm for CF-1 and NMRI mice, respectively. No statistically significant difference between either the slopes or the elevations of the concentration-effect curves was found, indicating the same level of sensitivity of CF-1 and NMRI mice regarding pulmonary irritation. It can be concluded that the 2 mice stocks gave qualitatively comparable responses, but regarding sensory irritation they responded differently quantitatively. Thus for sensory irritation investigations the RD50 values obtained with NMRI mice should be multiplied by 0.49 to obtain comparable values to those, expected in the recommended stock given by E981-84.