DNA brain damage after stress in rats.

OBJECTIVE: The purpose of this study was to verify the presence of DNA brain lesion after acute stress in rats. METHOD: Adult male Wistar rats were divided into 3 groups according to the stressor (control, forced swimming or restraint), and sampled at 2 time points: immediately or 1week after stress. Trunk blood and the brain areas (prefrontal cortex, amygdala and hippocampus) were extracted for DNA analysis by the comet assay. The cells were classified according to the damage index and damage frequency based on the comet tail size. RESULTS: Immediately after the stress, DNA damage was detected in the amygdala area and in the hippocampus after restraint and forced swimming. In the prefrontal cortex, DNA was damaged after forced swimming. However, no alteration was seen in blood. Seven days after the stress, DNA damage was still identified in the hippocampus after forced swimming and restraint, whereas no alteration was detected in the other brain areas or in blood. CONCLUSION: One week after a single stressful event, a reversible DNA damage was identified in the prefrontal cortex and in the amygdala, whereas DNA damage in the hippocampus still remained.

Pup age and aggressive behavior in lactating rats.

High levels of aggressive behaviors against intruders in the nest area are displayed by female rats during the first 10 days after delivery, declining thereafter to very low levels, even though lactation continues. Cross-fostering experiments were undertaken to test the hypothesis that pup age may affect aggression in lactating rats. The behavior of females on the 8th day after delivery when raising fostered 8-day-old pups was compared to that of females on the 8th postpartum day raising older pups (18 days old) for the last 5 days, and females on the 18th day after delivery raising fostered 18-day-old pups were compared to females in the same postpartum period nursing younger pups (8 days of age at the time of the maternal aggression test) for 5 days. Pup retrieval activity and plasma prolactin level were also analyzed. Females on the 8th postpartum day nursing 18-day-old pups were less aggressive than females in the same postpartum period, but with 8-day-old pups. Likewise, females on the 18th postpartum day nursing younger pups were more aggressive and presented higher levels of prolactin than females nursing older pups. Thus, pup development can alter the natural decline of maternal aggressive behavior.

Pup age and aggressive behavior in lactating rats

High levels of aggressive behaviors against intruders in the nest area are displayed by female rats during the first 10 days after delivery, declining thereafter to very low levels, even though lactation continues. Cross-fostering experiments were undertaken to test the hypothesis that pup age may affect aggression in lactating rats. The behavior of females on the 8th day after delivery when raising fostered 8-day-old pups was compared to that of females on the 8th postpartum day raising older pups (18 days old) for the last 5 days, and females on the 18th day after delivery raising fostered 18-day-old pups were compared to females in the same postpartum period nursing younger pups (8 days of age at the time of the maternal aggression test) for 5 days. Pup retrieval activity and plasma prolactin level were also analyzed. Females on the 8th postpartum day nursing 18-day-old pups were less aggressive than females in the same postpartum period, but with 8-day-old pups. Likewise, females on the 18th postpartum day nursing younger pups were more aggressive and presented higher levels of prolactin than females nursing older pups. Thus, pup development can alter the natural decline of maternal aggressive behavior

Technique for collecting cerebrospinal fluid in the cisterna magna of non-anesthetized rats.

We developed a technique for collecting cerebrospinal fluid (CSF) from the cisterna magna in non-anesthetized adult and young pup rats. In the adults, CSF was collected through a previously implanted guide cannula without previous disruption of the cisterna magna. In the pups, CSF was directly aspirated through a syringe from the cisterna in awake animals without previous surgery. In the adults, the volume of CSF collected varied from 50 to 120 microl, and in pups 7 to 10 days old, it was approximately 25 microl. The technique can easily be done by anyone who is familiar with stereotaxic surgery, and the material needed is cheap and easy to obtain commercially. A simple procedure to calculate the parameters for the implantation of guide cannula in rats other than Wistar ones is also presented.

Experimental observation of light-induced solitary waves of analyte bands in capillary electrophoresis.

The phenomenon of electrophoresis in free solution has been studied theoretically down to the molecular level for decades. In addition, intermolecular photo-induced proton transfer reactions, which occur in a wide class of molecules (phenols and aminoarenes) as well as proteins (green fluorescent protein), were also studied extensively. However, the study of the effect of light-induced electrophoretic mobility changes of the analytes in electrophoresis was begun only recently. In the present work, capillary zone electrophoresis was chosen as the environment to measure the magnitude of these electrophoretic mobility shifts induced by light. Background electrolytes (running electrolytes) with high refractive indices were developed, allowing the capillary to work like an optical fiber. The experimental conditions for obtaining stable coupling and guided laser light along the liquid core are discussed. Experimental evidence of band compression is observed, leading to a solitary wave behavior of the analyte band (2-naphthol). These solitary waves result from competition between thermal diffusion (dispersion mechanism) and a nonlinear (band compression) effect due to the combined electrophoresis phenomenon and absorption of guided light by the molecules of the band (which are subjected to a "reversible intermolecular proton transfer reaction" as one of their decay routes). The possibilities of applying this effect to different methods and techniques are also discussed.

Lesion of hypothalamic paraventricular nucleus and maternal aggressive behavior in female rats.

Lactating female rats on the 3rd to 12th day postpartum are more aggressive towards an intruder male than are nonlactating females. In this study, maternal aggressive behavior was recorded by introducing a strange male in the territory of the female and her offspring, on the fifth, seventh, and ninth day postpartum. Electrolytic lesions of the paraventricular nucleus of the hypothalamus (PVN) were performed on the fifth day postpartum. The results showed that the PVN lesion reduced the frequency and duration of attacks on the intruder. In addition, the lesion caused reduced weight gain in the pups compared to pups of the sham lesion group. The results suggest that PVN participates in the modulation of maternal aggression in rats. A possible role of oxytocin in that behavior is discussed.