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OP-12.- NEUROCHEMICALS, GENETICS AND AGGRESSION

OP-12.1.-ROLE OF 5-HT2A RECEPTOR AGONIST MICROINJECTED IN WISTAR FEMALE RATS IN THE DORSAL PERIAQUEDUCTAL GRAY AND MEDIAL SEPTAL AREA ON MATERNAL AGGRESSIVE BEHAVIOR

de Almeida*,  R.M.M.,  Giovenardi*, M.,  Baretta*, C. and Senger*, A.
Department of Psychology, Tufts University, Medford, MA, USA. *Curso de Psicologia,  Nucleo de Neurociencias da Universidade do Vale do Rio dos Sinos (UNISINOS), Brazil

Serotonin (5-hydroxytriptamine, 5-HT) has been implicated in the modulation of different forms of aggression in rodents. However, the numerous types of 5-HT receptors with different function and localization in several areas of the brain having various modulatory effects on aggression and defense make the interpretation of the results of 5-HT rather complex. The purpose of the present study was to analyze the role of  5-HT2A receptor agonist on maternal aggressive behavior. Female Wistar rats (90 days old and 230-270 g) were used. On day 4 post-partum the females were submitted to stereotaxic surgery to implant guide-cannula. On day 7 post-partum the animals were microinjected with the 5-HT2A receptor agonist, 5-methyl-alfa-hidroxytriptamine in different doses (0.2; 0.5;1.0 mg/0.2 ml) in the medial septal area (n=42) and dorsal periaqueductal gray (n=42) in the same doses. On day 7 post-partum the behaviors of lactating female rats with pups against a conspecific male intruder were recorded after 10 min the microinjection. The behaviors recorded were: sniffing the intruder, locomotion, lateral threat, lateral attack, frontal attack, bites and pup care. The results showed that in the dorsal periaqueductal gray  this agonist decrease the number of  bites the intruder, frontal attack and lateral attack in all doses studied. However, at a specific dosage (0.2 mg/0.2 ml), 5-a-methyl-hidroxytriptamine acting on postsynaptic receptors of the medial septal area  increase the number of bites the intruder. The doses of 0.5 and 1.0 mg/0.2 ml did not show difference when compared with group control. In conclusion, the effects of 5-a-methyl-hidroxytriptamine  depend on the area analysed and the dose utilized. In the dorsal periaqueductal gray the effects of this 5-HT2A receptor agonist is to decrease maternal aggressive behavior, but in the medial septal area a specific dose show a tendency to increase aggressiveness in female rats. 

OP-12.2.-EFFECTS OF CHROMIUM COMPOUNDS ON INCIDENCE OF SOCIAL AGGRESSION AND FERTILITY IN PREPUBERTAL MALE MICE

Homady,  M.H., Hussain*, H.H. and Tarawneh, K.A.
Department of Biological Sciences, Muítah University, Al-Karak-Jordan
*Department of Chemistry, Ottawa University, Ottawa, Ontario, Canada

The effects of ingestion of trivalent (chromium chloride) and hexavalent (potassium dichromate) chromium compounds were investigated on social aggression and fertility in male mice. Prepubertal male mice were exposed to these salts in drinking water at concentrations of 1000 and 5000 ppm for 90 days. The exposure of male mice to chromium chloride at 1000 or 5000 ppm significantly augmented social aggression. Fertility was significantly reduced in males exposed to the hexavalent chromium compound. The number of implantation sites and the number of viable fetuses in females impregnated by males exposed to this compound were significantly reduced.  The exposure of male mice to the trivalent chromium compound had, however, no effect on fertility. Body, testes, preputial gland and seminal vesicle weights were significantly suppressed in males exposed to the hexavalent compound but no such effects were evident in mice given the trivalent chromium compound. The results show that the ingestion of trivalent and hexavalent chromium compounds by male mice in prepubertal life have very different effects on both social aggression and fertility. Only potassium dichromate produced a pattern of responses clearly indicative of suppressed gonadal function.

OP-12.3.-EFFECTS OF GENETIC SELECTION FOR LACK OF AGGRESSION TOWARDS HUMANS ON REPRODUCTIVE PHYSIOLOGY IN THE SILVER FOX

Osadchuk, L.V.
Institute of Cytology and Genetics, Siberian Department of the Russian Academy of Sciences, Novosibirsk, Russia

Artificial selection for absence of aggressive response to humans and docility plays a key role in the domestication process. To establish genetic and physiological mechanisms of the early evolution of domestic animals, a model of silver fox domestication was developed at our institute by long-term selection for lack of aggression and fear towards humans (domestic behaviour). This study was designed to examine possible changes in the reproductive physiology of selected foxes. The levels and the in vitrogonadal production of reproductive hormones (testosterone, oestradiol and progesterone) were measured in selected and control foxes. Additionally sperm production, potential fertility, embryonic mortality and reproductive behaviour were assessed. The significant differences were found between selected and control animals throughout the reproductive cycle, pregnancy, and prenatal life, and also in responses of the reproductive system to different environmental conditions. The study has shown that increased progesterone output in domesticated vixens during oestrous and preimplantation period of pregnancy might be a part of the endocrine mechanism involved increased potential fertility that has been attained by selection. It has been established the timing shift of the annual rhythm of ovarian activity and a depressed relationship between photoperiod and endogenous hormonal cycles in selected fox vixens. Domesticated vixens were also more resistant to the detrimental effects of the artificial photoperiods on hormonal secretion and fertility. The shorter period of testicular activity, lower sperm production and lower sexual activity was found in selected males. Selection against aggression towards humans also reduced sexual and increased agonistic behaviour in males during bisexual encounters. The study of fetal development indicated to heterochrony in the pituitary-testicular axis in selected animals. In conclusion, selection of silver foxes for the absence of aggression towards humans resulted in a number of changes in reproductive function and its hormonal control, and a new genetically determined level of gonadal activity was established. The data obtained has led to a conception that this type of selection can bring about for a short time period a considerable destabilisation in the pituitary-gonadal axis. In addition, at present time various wild species bred in captivity can be selected for confidence to humans unconsciously, and this selection ultimately will provoke correlative alterations in reproduction.