Developmental expression of sexual differences in open-field behaviour and plasma cholinesterase activity in male, female and masculinized female rats

Sabe-se que algumas diferenças sexuais no metabolismo e no comportamento estäo relacionadas com o efeito neonatal da testosterona e outras näo sofrem esse tipo de influência. O objetivo desses experimentos foi estudar o desenvolvimento das diferenças sexuais na atividade da colinesterase plasmática e de determinar se essas diferenças seriam relacionadas com a exposiçäo pós-natal à testosterona em ratos. A atividade geral no campo aberto foi também verificada como um indicador comportamental das açöes da testosterona na diferenciaçäo sexual do sistema nervoso central. Foram usados três grupos de animais: machos normais, fêmeas normais e fêmeas masculinizadas (1 mg testosterona, SC, no 2§ dia de vida pós-natal). A atividade geral no campo aberto foi medida durante três dias consecutivos logo após o desmame (21-23 dias de idade), durante o início da puberdade (30-36 dias de idade) e nos adultos (90-110 dias de idade); a atividade da colinesterase plasmática foi medida aos 22, 30-36 e 90-110 dias de idade. Como esperado, foi encontrada uma diferença sexual no campo aberto entre machos e fêmeas normais. O tratamento pós-natal com andrógeno nas fêmeas diminuiu a atividade no campo aberto na idade adulta a padröes similares àqueles observados para machos normais. Foram observadas diferenças similares logo após o desmame, mas näo aos 22 e aos 30-36 dias de idade. Em contraste, foram observadas diferenças significantes na atividade da colinesterase de animais adultos mas näo nos dias 22 e 30-33 dias de idade. Quando comparadas às fêmeas normais, as fêmeas masculinizadas näo apresentaram diferenças na atividade da colinesterase plasmática, sendo que esses dois grupos foram diferentes dos machos. Esses resultados sugerem que as diferenças sexuais na atividade da colinesterase plasmática de ratos adultos, näo säo dependentes de exposiçäo à testosterona durante o início da vida pós-natal. Além disso os resultados demonstram que sob esse estresse (desmame) as diferenças sexuais no comportamento no campo aberto podem ser observadas já aos 21-23 dias de idade

Pro and anticonvulsant effects of xylazine on convulsion models in rodents.

Pretreatment of mice with 30 mg xylazine/kg ip protected against convulsions induced by amphetamine, but it intensified pentylenetetrazole- and strychnine-induced seizures. Xylazine pretreatment also protected rats against electroshock-induced convulsions. These findings support a noradrenergic mechanism being involved in the proconvulsant and/or anticonvulsant effects of xylazine.

Behavioral and biochemical effects of Xylazine: possible interactions between central noradrenergic-dopaminergic systems

Alguns efeitos comportamentais e bioquímicos da xilazina foram estudados em ratos e camundongos. Os resultados mostraram que a xilazina: a)diminuiu a atividade geral de ratos e camundongos observados em campo-aberto; b) foi incapaz de produzir catatonia e suprimiu este comportamento induzido pelo haloperidol em camundongos; c) potencializou o comportamento estereotipado induzido pela apomorfina em ratos; d) aumentou os nívei cerebrais de noradrenalina, porém näo alterou aqueles de dopamina. Estes resultados foram discutidos considerando-se açäo da xilazina em sistemas noradrenérgicos centrais e da interaçäo entre sistemas noradrenérgicos e dopaminérgicos centrais

The relationships between neuronal activity and behavioral seizures induced by Palicourea marcgravii in rats.

To characterize the convulsions induced by an aqueous extract of Palicourea marcgravii (Pm), male Wistar rats were injected sc with 3.75 g/kg of the extract, and electroencephalogram and behavior were observed for periods up to 180 min after the Pm injections. Sleep spindles and generalized convulsive seizures were observed following Pm administration. Spiking activity was detected in both cortical and hippocampus recordings. They lasted approximately 2 min and were followed by a period of postical depression and/or death. These results agreed with previous behavioral experiments which suggested the toxic effect of Pm aqueous extract was mainly at the central nervous system level.

Effects of bracken fern (Pteridium aquilinum L Kuhn) feeding during the development of female rats and their offspring.

Bracken fern (Pteridium aquilinum L Kuhn), is widely food in many parts of the world; the toxic effects have been demonstrated on many species of animals, and both carcinogenicity and enzootic hematuria has been studied. We investigated the effects of feeding bracken fern on the development of female rats and their offspring. The plant was fed as 30% of the normal diet on an ad libitum basis. Bracken fern did not modify the weight gain of the female rats during development, nor affect estrus cycle duration or milk production, the plant did reduce female fertility and weight gain during pregnancy. It also adversely affected physical and neurobehavioral development in the offspring.

Effects of prenatal pyrethroid insecticide exposure on the sexual development of rats.

The prenatal effects of exposure to the insecticide cyhalothrin on the sexual maturation and sexual behavior of rats were investigated. Female rats were dermally treated with 1 ml/day of 0.02% (w/v) aqueous cyhalothrin solution or its vehicle throughout pregnancy. This insecticide administration delayed the age of testicle descent but did not modify the age of vaginal opening. In adulthood, both male and female rat sexual behaviors were not different from vehicle-treated animals. It was concluded that prenatal exposure to cyhalothrin can induce alterations in the development of certain physical characteristics of rats which are not correlated with functional deficiencies in the animals' later life.

Pyrethroid insecticides and pregnancy: effect on physical and behavioral development of rats.

We investigated the prenatal effects of cyhalothrin exposure on the physical and behavioral development of infant and adult rats. Female rats were treated by dermal exposure with a 0.018% cyhalothrin aqueous solution (1 ml/d) or the cyhalothrin vehicle during their entire pregnancy. The pesticide delayed development of fur, the ear and eye openings and descent of the testes in the offspring. The exploratory behavior of the rats prenatally exposed to cyhalothrin decreased. No differences were observed between control and experimental animals in inhibitory avoidance tasks at 90 d of age in open field activity. Alterations in physical parameters and possible effects of the pesticide on epidermal growth factor and hormonal levels were considered. Since no overt of signs of maternal or neonatal toxicity were observed, the decrease in adult motivational behavior was attributed to a specific effect of the pesticide administered during the prenatal period. We concluded that prenatal cyhalothrin exposure induced subtle and persistent changes in the physical development and behavior of rats.