Effects Of Amitraz Research Articles

Evaluation of different treatments in control of Oligonychus afrasiaticus in date palm orchards of Iran

Oligonychus afrasiaticus is a major pest of date palm orchards in Iran and Middle East countries. Effects of amitraz, fenpropathrin, fenpyroximate, fenazaquin, propargite), tetradifon, and hexythiazox were evaluated in southern part of Iran. The complete randomized block designed with three replications used on Mordarsang, Kabkab, Barhi, Mazafati, and Halileh major date varieties cultivated in Hormozgan, Bushehr, Khuzestan, Kerman and Sistan and Baluchistan provinces, respectively. Two small date clusters randomly were detached from each replicate and number of spider mite mobile stages were counted on epidermis of 20 date fruits at intervals one day before, 3, 7, 14 and 20 days after treatments. Mean mite densities before treatments found varied from 1.4–69 mites among treatments, provinces and year of studies. Mean mortality analysis variance was found significant (p > 0.01) in all factors. First and last sign of web span around date fruits cluster observed in Khuzestan, and Sistan and Baluchistan in April–May and July–August, respectively. High, medium and weak treatment mortality percentage during 3 rd day sampling time in two years recorded for Hormozgan, Kerman, Khuzestan, Bushehr, and Sistan and Baluchistan provinces. Absolute mite pest control obtained at 20 th day sampling time during 2 nd year in Kerman and imperfection mortality in other places in two years. Date spider mite treated with tetradifon has a half century history in Iran and fenazaquin with low dose (0.3%), caused high mortality rate in most of provinces. Absolute mite controlled (100%) and prolongation effects recorded by water sprayed during 20 th day sampling time in the 1 st and 2 nd year in Hormozgan and Kerman provinces, respectively.

Reproductive and Developmental Toxicity of Amitraz in Sprague-Dawley Rats

The present study was conducted to obtain information on the effects of amitraz on reproductive and developmental parameters in rats. The test chemical was administered via the drinking water containing 0, 40, 120, and 360 ppm to male rats from 2 weeks before mating to the end of 14-day mating period and to females from 2 weeks before mating, throughout mating, gestation and up to lactational day 4. During the study period, clinical signs, body weights, food intake, organ weights, reproductive and littering findings, necropsy findings, sperm parameters, and histopathology were examined. At 360 ppm, decreases in the body weight gain, food consumption, and the number of live pups and an increase in the post-implantation loss were observed. In addition, decreases in the seminal vesicle weight and sperm motility were found in males. At 120 ppm, a decrease in the food consumption was found transiently in both males and females, but no reproductive and developmental toxicity was observed in both sexes. There were no signs of either general or reproductive and developmental toxicity in the 40 ppm group. Based on these results, it was concluded that the repeated oral administration of amitraz to rats resulted in a decrease in the food consumption at 120 ppm and decreases in the seminal vesicle weight, sperm motility, and the number of live pups and an increase in the post-implantation loss at 360 ppm in rats. Under these experimental conditions, the no-observed-adverse-effect level (NOAEL) of amitraz for general and reproduction/developmental toxicity was believed to be 120 ppm, and the no-observed-effect level (NOEL) of amitraz was believed to be 40 ppm in rats.

A study on immunotoxicological effects of subacute amitraz exposure in rats

The effects of amitraz, a formamidine pesticide, were investigated in four-week old outbred male Wistar rats on certain classic toxicological and haematological parameters as well as on specific immune functions. The animals were treated, per os by gavage for 28 days, in a five-day treatment two days break system, with 26.5, 21.1, 10.6 and 5.29 mg/kg/day amitraz. On the 29th day, organ weights of the thymus, heart, lung, spleen, liver, kidneys, adrenals, testicles and popliteal lymph node; WBC and RBC counts, Ht, MCV, haemoglobin; and cell content of the femoral bone marrow were determined. In two separate groups, the effects of amitraz on the PFC content of the spleen, and on the maximum level and time course of DTH reaction, were investigated. Amitraz in 26.5 mg/kg dose increased relative adrenal weight, and decreased relative liver weight, MCV value, PFC content of the spleen, and the maximum level of DTH reaction. The 21.1 mg/kg dose decreased only MCV value, while 10.6 mg/kg elevated the liver-to-brain weight ratio. Based of these findings, a NOEL dose of 5.29 mg/kg was determined for amitraz in this experimental system; while the LOEL doses were 10.6 mg/kg for the general toxicological, 21.1 mg/kg for the haematological and 26.5 mg/kg for the immune function parameters. The results show that the exposure sensitivity of these immune functions to amitraz is lower than that of some other toxicological and haematological parameters.

Effects of amitraz on cytochrome P450-dependent monooxygenases and estrogenic activity in MCF-7 human breast cancer cells and immature female rats

This study investigated the ability of amitraz, a formamidine insecticide, to induce cytochrome P450-dependent monooxygenases and to disrupt estrogenic activity in human breast cancer MCF-7 cells and immature female rats. In MCF-7 cells, treatment with 10 μM amitraz for 24 h increased 7-ethoxyresorufin O-deethylase activity in cell homogenate. Treatment of MCF-7 cells with 1 and 10 μM amitraz for 3 h replaced previously bound [ 3H]17β-estradiol (E 2) from estrogen receptors. Treatment with 0.1 and 1 μM amitraz for 2 days inhibited [ 3H]thymidine incorporation into the DNA of MCF-7 cells while the inhibition was blocked in cells co-treated with 1 nM E 2 and amitraz. In immature female rats, treatment with 50 mg/kg amitraz intraperitoneally for 3 days increased cytochrome P450 content, 7-ethoxyresorufin, methoxyresorufin and pentoxyresorufin O-dealkylases, and benzo[ a]pyrene hydroxylase activities in liver microsomes. The results of immunoblot analysis revealed that amitraz induced liver microsomal CYP1A1/2, 2B1/2B2, and 3A proteins. Treatment with 10 and 25 mg/kg amitraz for 3 days dose-dependently decreased uterine weight and peroxidase activity in immature female rats while the decreases were blocked in rats co-treated with 10 μg/kg E 2 and 10 or 25 mg/kg amitraz. These in vitro and in vivo findings suggest that amitraz induces multiple forms of P450 and exerts weak antiestrogenic activity.

Amitraz depresses cardiovascular responses to bilateral carotid occlusion.

The ectoparasiticide amitraz stimulates alpha 2-adrenoceptors to produce side-effects such as bradycardia and hypotension. The actions of amitraz on baroreceptor reflex responses were evaluated in mongrel dogs by occlusion of both carotid arteries for 30-s periods. Incremental doses of amitraz given intravenously showed that doses of 60 micrograms/kg and above significantly depressed pressor responses to carotid occlusion. By comparison, 2 micrograms/kg amitraz given by intracisterna magna (i.c.m.) injection significantly depressed both blood pressure and heart rate responses. Pretreatment of dogs with i.c.m. yohimbine (30 micrograms/kg) prevented the depressant effects of amitraz on the reflex, but prazosin (20 micrograms/kg), in separate experiments, had no effect.

Effect of Amitraz on Colorado Potato Beetle (Coleoptera: Chrysomelidae) Feeding, Development and Survival

Effects of amitraz, a formamidine insecticide, were studied in Colorado potato beetle, Leptinotarsa decemlineata (Say), populations from Minnesota, North Dakota and Virginia. Contact exposure or ingestion of leaves dipped in 4000 ppm amitraz was not lethal to adults. However, adult feeding was reduced 50% upon exposure to 90 ppm amitraz, a rate <1/8 that recommended by the manufacturer for testing as a foliar insecticide. Ingestion of foliage treated with 945 ppm amitraz by early instar larvae had long-term effects on Colorado potato beetle development and survival, delaying adult emergence 4.7 days and causing 87% mortality. In 72 h bioassays, LC50s by contact exposure or ingestion were > 3.2× the suggested field rate. LC50s determined by exposure of larvae to treated foliage were greater than LC50s determined by immersing larvae. Egg hatch was not reduced by application of ≤ 1840 ppm amitraz. In field trials, amitraz reduced defoliation as effectively as esfenvalerate, the insecticide of choice when these trials were conducted. Amitraz-treated plots had yields intermediate between esfenvalerate and control treatments.

Effects of amitraz on motor function.

The effects of amitraz, a formamidine derivative, on motor function were studied in rats. Behavioural and neurochemical studies were performed. Results show that amitraz was able: 1) to decrease locomotion and rearing frequencies of rats and to increase their immobility time in an open-field; 2) to displace to the left the control dose-response curve constructed to apomorphine-induced stereotyped behavior; 3) to potentiate both pentobarbital sleeping time and amphetamine effects on open-field behaviour of rats and 4) to increase not only the whole brain levels of noradrenaline but also the striatal levels of dopamine. In relation to control animals, the pesticide also induced 5) a decrease in the striatal levels of homovanillic acid, 6) pesticide effects on open-field behaviour of rats were not antagonized by yohimbine administration, and 7) metoclopramide administration on amitraz pretreated rats antagonized not only amphetamine effects on open-field behaviour, but also apomorphine-induced stereotypy. These results are discussed in the light of the actions of amitraz on biogenic amines. It is suggested that the pesticide effects on motor function are consequences of the inhibitory effects on MAO activity, most probably through the increases produced on catecholamine levels within the central nervous system.

Efeitos do praguicida amitraz no comportamento agressivo induzido pelo isolamento social em camundongos

Estudaram-se os efeitos do amitraz, um derivado formamidínico, no comportamento agressivo induzido pelo isolamento social em camundongos. Os resultados mostraram que o amitraz aumentou a latência para o primeiro ataque e diminuiu não somente a duração de briga como as freqüências de ataques entre esses animais. Estes resultados sugeriram que os efeitos do praguicida sobre o comportamento agressivo dos camundongos foram conseqüência de um efeito inibitório do mesmo sobre a atividade da enzima monoamina oxidase no Sistema Nervoso Central, e, conseqüentemente, de um aumento dos níveis cerebrais de serotonina.

Rat strain and stock comparisons using a functional observational battery: Baseline values and effects of amitraz

A functional observational battery (FOB) was utilized to assess the effects of 3-day exposure to the formamidine pesticide amitraz in outbred Sprague-Dawley-derived and inbred Fischer-344-derived (F344) rats (both from Charles River Laboratories) and in outbred Long-Evans rats obtained from two commercial suppliers (Charles River Breeding Laboratories and Blue Spruce Farms). Significant strain and stock differences were obtained in baseline values for one-third of the FOB measures. In most cases, F344 rats were different from the others. Characteristic signs of amitraz exposure consisting of increased excitability, hyper-reactivity and physiological and autonomic changes were evident in all treated rats. These effects increased with repeated dosing, and many were still present 6 days after dosing. On individual measures, there were differences between the strains and stocks in terms of sensitivity and time course of amitraz effects. In general, Blue Spruce Long-Evans rats displayed more effects of amitraz and F344 rats recovered more quickly than others. Although Sprague-Dawley rats showed the least effect overall, they displayed the largest increases in the sensorimotor responses to stimuli. These data indicate that although some behavioral and physiological parameters showed strain and supplier differences, in both baseline values and the effects of amitraz, conclusions concerning its neurotoxic potential in a screening context would be similar.

Formamidine pesticides enhance susceptibility to kindled seizures in amygdala and hippocampus of the rat

Electrical kindling of the amygdala and hippocampus was used to evaluate the effects of two formamidines, chlordimeform (CDF) and amitraz (AMZ), upon seizures susceptibility in the rat. Male Long-Evans rats were implanted with electrodes in the amygdala or dorsal dentate gyrus, and injected IP daily with 40 mg/kg CDF, 50 mg/kg AMZ, or equal volumes of their respective vehicles. Afterdischarge (AD) thresholds were determined after the first injection. Animals were then stimulated twice daily, 2 and 4 hours postinjection, at a standard 200 μA stimulus intensity until three stage 5 generalized seizures ensued. Both CDF and AMZ significantly facilitated amygdaloid kindling rate, and CDF also facilitated hippocampal kindling rate. The effects of AMZ on hippocampal kindling were not assessed. AD durations were prolonged in the formamidine-treated groups, but there was no effect on AD thresholds. The alpha-2 adrenergic agonist and/or local anesthetic-like properties of these compounds may be responsible for these seizure enhancing effects.

Investigations of amitraz neurotoxicity in rats: I. Effects on operant performance

Amitraz (AMZ) is a formamidine pesticide which is often compared to chlordimeform (CDM). The effects of AMZ (6.25–75 mg/kg) and CDM (5–20 mg/kg) on the schedule-controlled performance of rats were examined using a multiple fixed-ratio (FR) 10 fixed-interval (FI) 300-sec schedule of milk reinforcement. Following dose-effect determinations, rats received three daily doses of AMZ (50 mg/kg). Low to intermediate doses of AMZ (6.25-25 mg/kg), administered 20 min presession, significantly decreased FI responding but not FR responding. In contrast, CDM appeared to decrease responding similarly under both components. Both compounds disrupted the temporal pattern of responding within the interval; AMZ had only a moderate influence at all effective doses but CDM produced a marked dose-dependent disruption of temporal response patterning. The effects of the high doses of AMZ (50–75 mg/kg) were more pronounced 24 hr after dosing, whereas the rats had recovered from lower doses at this time. Performance was progressively disrupted and the rats' health rapidly deteriorated during the course of three daily injections of AMZ (50 mg/kg). Operant performance recovered more quickly than did the general health of the rats. Thus AMZ produced effects on multiple-schedule performance that were distinct from the effects of CDM. Moreover, the signs of intoxication and the effects on schedule-controlled behavior following a high dose (50 mg/kg) were augmented and persistent with short-term repeated administration.

Effects of formamidines on the population growth of Tetranychus urticae Koch

The formamidines chlordimeform, amitraz, and N 2-(4-n-butylphenyl- N′, N′-dimethylformamidine (BDMF) caused a reduction in survival and fecundity which significantly decreased the intrinsic rate of increase of population growth of the two-spotted spider mite, Tetranychus urticae Koch. Amitraz was the most potent inhibitor of population growth; chlordimeform was intermediate, and BDMF was least potent. Effects of amitraz on population growth were attributable mainly to its lethal action on the various life stages, whereas BDMF inhibited fecundity. The activity of chlordimeform was attributed to its lethality to life stages as well as to its inhibition of fecundity.

Effect of amitraz and chlordimeform on heart rate and pupil diameter in rats: Mediated by α2-adrenoreceptors

Pupillary and cardiac responses to the insecticide/acaricide amitraz (0.03 to 1.0 mg/kg, iv) and chlordimeform (0.03 to 10.0 mg/kg, iv), as well as the α 2-adrenergic agonists clonidine (1 to 30 μg/kg, iv) and xylazine (10 to 300 μg/kg, iv), were investigated in rats anesthetized with an ether and pentobarbital combination. Amitraz, clonidine, and xylazine caused a dose-dependent mydriasis and bradycardia. The order of potency of the mydriatic and bradycardic effects was: clonidine > xylazine > amitraz. Chlordimeform did not cause mydriasis or bradycardia at the dosages studied. Amitraz-induced mydriasis and bradycardia were blocked by antagonists with α 2-adrenoreceptor blocking activity: yohimbine and phentolamine (2.5 mg/kg each, iv). In contrast, these effects of amitraz were not affected by prazosin (2.5 mg/kg, iv), an α 1-adrenoreceptor antagonist. In rats pretreated with reserpine (7.5 mg/kg, sc, 20 hr) and α-methyl- p-tyrosine (250 mg/kg, ip, 5 hr) to deplete catecholamine, amitraz (0.03–1.0 mg/kg, iv) produced mydriasis of similar magnitude as in the control animals. However, amitraz did not lower the heart rate in the pretreated animals as it did in the control animals. The results demonstrated that amitraz, a formamidine, induced mydriasis and bradycardia which were not observed with administration of another formamidine, chlordimeform. The data also suggest that amitraz-induced mydriasis is mediated by postsynaptic α 2-adrenoreceptors while amitraz-induced bradycardia is mediated by presynaptic α 2-adrenoreceptors.