Brat. J. vtl. R u. anim. Set., Sao Paulo, v. 30, it. 1, p. 17-9,1993.

EFFECTS OF AMITRAZ ON ISOLATION-INDUCED AGGRESSION IN MICE

EFEITOS DO PRAGUICIDA AMITRAZ NO COMPORTAMENTO AGRESSIVO INDUZIDO PELO ISOLAMENTO SOCIAL EM CAMUNDONGOS

Michiko SAKATE1; Jorge Camilo FLÓRIO1; Joào PALERMO NETO*

SUMMARY

The effects of amitraz, a formamidine derivative on isolation-induced aggression were studied in mice. Results show that amitraz increased the latency to the first attack and increased not only the fight duration but also the frequencies of attacks and tail (lickings. These results suggested that pesticide effects on aggressive behavior could be a consequence of it’s inhibitory effects on monoamine oxidase activity within the Central Nervous System, most probably through the incre­ ments it produces on serotonin levels.

UNITERMS: Amitraz; Aggressive behavior; Social isolation; Serotonin; Catecholamines; Mice

Contrarily to other pesticides, amitraz, a formamidine deriva­ ment, the mice were individually housed in opaque plastic tive, widely used in Veterinary clinical practice for the treat­ cages (26 x 14 x 19 cm) in a controlled room temperature ment of demodicosis11 does not stimulate Central Nervous (22°C ± 1) with a 12 h light cycle (lights on from 7 a.m.); System (CNS). Although! acute intoxications with this pesti­ food and water were provided ad libitum, except during ob­ cide are not common, signs and symptons of CNS depression servation periods when they were withdrawn. Animals were such as sedation, loss of the righting reflex, motor incoordi­ used once. nation and coma were already described after it’s use on large doses 19. The dose of 195 mg/kg was that reported to be the The mice were equally and at random divided into four groups: oral and acute amitraz (Triatox®) LDW in male rats14. one control and three experimental groups; the animals of the experimental groups were intraperitonially treated with 0.5; Amitraz induced depression, however, is not unespecific. 20.0 or 50.0 mg/kg of Amitraz (Triatox® Coopers do Brasil Pesticide affects were already related to an MAOI-like action S/A) 90 min. before aggressiveness evaluation. Animals of within the CNS; indeed, it was shown that it inhibited mono­ the control group were similarly treated but with distilled amine oxidase (MAO) activity both in liver and brain of rats' water (0.1 ml/lOg), being also observed for aggressive behav­ and also that it crosses the blood brain barrier4. Recently, it was ior 90 min. after treatment. These pesticide doses were choosen found that perinatal exposure to amitraz induced develop­ since they were able to change animal’s open-field behavior mental changes and alterations in the motor function of rat as observed on previous work5. pups*. Acute amitraz administration increased also pentobarbital sleeping time in mice and the convulsive thresh­ Aggressive behavior was induced by isolation (28 days) be­ old doses of rats to several convulsants5. Since amitraz ad­ ing recorded for 10 min. according to the method described ministration induced many behavioral alterations in rats, in­ by VALZELLI et al.'5. Hand-operated counters and stop­ creasing at the same time the levels of noradrenaline, dopamine watches were employed to score the following parameters: and serotonin in different brain regions of these treated ani­ latency to the 1“ attack (time in s to the 1“ attack), fight dura­ mals**, we thought it would be interesting to evaluate the tion (total s of fight), attack frequency (number of attacks) effects of acute amitraz intoxication on isolation-induced ag­ and tail flicking frequency (number of tail flickings). To gression in mice. Indeed, the expression of this kind of ag­ minimise possible circadian changes in mice’s behavior, con­ gressive behavior was already related to the activation of sev­ trol and experimental observations were altemed, the mice eral brain amine pathways within the CNS". Thus, the results being observed al the same time of the day (between 8:00 and to be observed could bring some new data to the understand­ 13:00 h). Since the obtained results were homocedastic an ing of the underlying mechanisms involved on amitraz ef­ analysis of variance (ANOVA) followed by Duncan’s lest fects. was used to analise all data. Results were considered signifi­ cant when p < 0.05. Fifty six male Swiss Webster mice weighing initially 25-30 g at the beginning of the experiments and of the same strain As it can be seen in Fig. 1, amitraz administration was able to were used. From 28 days before the beginning of the experi­ decrease isolation-induced aggression in mice. Thus, pesti-

• SAKATE. M.; FLÓRIO, J.C.; PALERMO NETO. J. Developmental and behavioral effect* of prenatal amitraz administration in rau. Arch. 1- PhD - Botucatu of Veterinary Medicine UN ESP Toxkol. (No prelo) 2- PhD - School of Veterinary Medicine, Univenily of Sâo Paulo ** FLÓRIO, J.C.; SAKATE. M.; PALERMO NETO. J. Effect* of amitrax 3- Profeiior - School of Veterinary Medicine, Univenity of SIo Paulo on motor function. Pharmacol. Toxicol. (No prelo)

17 SAKATE, M.; FLOrIO, J.C.; PALERMO NETO, J. Effccts of amitraz on isolation-induccd aggression in micc. Braz. J. vet. Res. anlm. Sd., SSo Paulo, v. 30. n. 1, p. 17-9,1993.

cide administration increased in a dose-dependent way the de ataques entre esses animais. Estes resultados sugeriram latency to the 1“ attack (F=12.44; df=3/24; p<0.05) and de­ que os efeitos do praguicida sobre o comportamento agressi­ creased also in a dose-dependent way, not only the attack vo dos camundongos foram conseqüência de um efeito inibi- frequency (F=10.5; df=3/24; p<0.05), but also the fight dura­ tório do mesmo sobre a atividade da enzima monoamina tion (F=3.57; df=3/24; p<0.05) and the tail flicking frequency oxidase no Sistema Nervoso Central, e, conseqüentemente, (F=4.71; df=3/24; p<0.05). Further analysis of micc behavior de um aumento dos níveis cerebrais de serotonina. after amitraz administration showed that animals presented not only sedation but also motor incoordinations; these signs UNITERMOS: Amitraz; Comportamento agressivo; were detected 10 min. after the 50.0 mg/kg dose, 20 min. Isolamento social; Serotoninas; after the 20 mg/kg dose and 80 min. after the smaller pesti­ Calecolaminas; Camundongos cide dose (0.5 mgAg), lasting for at least 24 h.

According to FL6RIO et al.** amitraz administration in rats, AKNOWLEDGEMENTS through it’s MAOI-like activity, increased the whole brain levels of noradrenaline, the striatal levels of dopamine and This work, part of the PhD thesis presented by M. Sakate to the brain stem levels of serotonin, decreasing at the same the School of Veterinary Medicine of the University of Süo lime the striatal levels of homovanilic acid and the brain stem Paulo, was supported by a fellowship from PADCT/CAPES. levels of 5-hydroxyindoleacetic acid. Since changes in ag­ gressive behavior of laboratory animals arc often associated with modifications in brain monoamine turnover or levels" REFERENCES the present results could be a consequence of pesticide effccts on catecholaminergic and/or on serotoninergic pathways. 01-BONSALL, J.L.; TURBULL, G.J. Extrapolation from safety data to management of poisoning with reference to amitraz (a DOPA per se or combined with MAO inhibitors induces irri­ formadine pesticide) and xylene. Human. Toxicol., v.2, p.578- 92, 1983. tability and fighting in rats and mice4. Under certain condi­ tions aggressiveness is positively related to brain noradrena­ 02-BUUS-LARSSEN, J. Piperoxan reduce the effects of clonidtne line levels15. Thus, amitraz effccts might not be attributed to on aggression in mice and on noradrenaline dependent modifications in catecholaminergic pathways; indeed, pesti­ hypermolilily in rais. Europ. J. Pharmacol., v. 47, p.47-9. 1978. cide administration reduced isolation-induced aggression and, as observed previously, induced sedation and motor incoordi- 03-EIDELBERG, E.; GOLDSTEIN. G.P.; DEZAN, L. Evidence for nation2-5*. serotonin as a possible inhibitory transmitter in some limbic structures. Exp. B rain Res., v. 4, p. 73-80, 1976. Serotonin depletion causes excitability and aggressiveness10 04-EVERETT, G.M.; BORCHERDING, J.W. 1-DOPA effect on which suggests an inhibitory influence for this amine on be­ concentrations of dopamine, norepinephrine and serotonin in havior. It was already demonstrated that the firings of the brains of mice. Science, v. 168, p.549-50, 1970. axosomatic synapses containing 5-HT of the amygdaloid neu­ 05 FLORIO, J.C.; SAKATE. M.; PALERMO NETO. J. Some be­ rons, decreased sharply alfer 5-hydroxytryptophan (5-HTP) havioral effects of the pesticide amitraz. Braz. J. Med. Hlol. administration5. The administration of 5-HTP suprcsscs not Res., v.22, p.1291-3, 1989. only the mouse-killing behavior of rats, but also the aggres­ 06-FAO. Plant production and production paper. Pestk. Residues sive behavior induced in rats by PCPA administration and the Food Evaluation, v. 26, p. 1-59, 1980. Suplcmento. isolation-induced aggression in mice". Consequently, a pos­ 07-FOLZ, S.D.; KAKUK, T.J.; HENKE. C.L.; RECTOR, D.L.; sible hypothesis to explain the present observed decrease in TESAR, F.B. Clinical evaluation of amitraz as a treatment mice aggressiveness would be the increment induced by for canine demodicosis. V e t Paraslt., v. 16, p. 335-41, 1984. amitraz on brain serotonin levels. Thus the possibility in raised 08-GILBERT, M.E.; DYER, R.S. Increased hippocampal excitabil­ that amitraz effects on isolation-induced aggression in mice ity produced by amitraz. Neurotoxkol. Theratol., v. 10, p. were also a consequence of it’s MAOI-like effects. Accord­ 229-35, 1988. ingly, MAOI agents such as pargyline decreased inter-male aggression in rats". It should not be forgotten, however, that 09-HSU, W.H.; SCHAFFER, D.D. Effects of topical application of amitraz on plasma glucose and insulin concentrations in dogs. amitraz is also an agonist at alpha^ adrenoceptors* since these Amer. J. vet. Res., v. 49, p. 130-1, 1988. receptors were already related to aggressive behavior2. 10-KOE, B.K.; WE1SSMAN. A. The pharmacology of parachlorophenylalanine, a selective depletor of serotonin stores. Advanc. Pharmacol., v. 6B. p. 29-47, 1968. RESUMO 11-MASON, S.T. Catecholamines and behavior. Cambridge, Estudaram-se os efeitos do amitraz, um derivado Cambridge University Press, 1984. p. 96-165: Catecholamines and pathological behavior. formam idínico, no comportamento agressivo induzido pelo isolamento social em camundongos. Os resultados mostraram 12-MULLER, G.H. Amitraz treatment of demodicosis. J. Amer. que o amitraz aumentou a latftncia para o primeiro ataque e Anlm. Hosp. A » ., v. 19, p. 435-41, 1983. diminuiu não somente a duração de briga como as frcqüSncias 13-RANDRUP, A.; MUNKVARD. I. Relation of brain cat-

* SAKATE, M ; FLÔRIO, J.C.; PALERMO NETO, J. Developmental and behavioral effecu of prenatal amitraz administration in rats. Arch. Toxicol. (No pccio) •• FLÓRIO, J.C.; SAKATE, M.; PALERMO NETO, J. Effects of amitraz on motor function. Pharmacol. Toxicol. (No prelo)

18 SAKATE, M.; F1j6RIO, J.C.; PALERMO NETO, J. Effccts of amilraz on isolation-induced aggression in micc. Bra/. J. vet. Res. anim. ScL, Sao Paulo, v. 30, n. 1, p. 17-9,1993.

excitation. In: GARATTTNT, S.; SIGG, E.B., eds. Agressive 15-VALZELLI, L. Drugs and agressiveness. In: GARATTINI, E.; behavlor. New York, Willey, 1969. p. 228-35. SHORE, P. A., eds. Advances in pharmacology. New York. Academic Press, 1967. v. 5, p. 79-108. 14-SAKATE, M. Efeitos comportamentals do Amitraz (Triatox®). S8o Paulo, 1991. Tese (Doutorado) - Faculdade de Medicina Recebido para publicação cm 10/08/92 Veterinária e Zootecnia, Universidade de São Paulo. Aprovado para publicação em 12/11/92

FIGURK 1 EffecU of amilraz administration (stripped columns) on isolation induccd aggression in micc. Amitraz was administered inlrapcritonially 90 min. before behavioral evaluations. * p<0.05 in relation to control data (open columns - analysis of variance, Duncan's test).

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