ABSTRACT
Objective To explore the effect of the different doses of oxytocin(OXT) on stress model aggressive behaviour in Wistar rats.Methods According to random number table,40 pregnant rats were divided into experimental stress groups (A, B, C) and control group(D) with 10 samples in each group.Before forced swimming test, rats in experimental groups (A, B, C)were given OXT via intraperitoneal injection with 0.3 mg/kg, 1.0 mg/kg,2.0 mg/kg;rats in group D were given equal volume of normal saline in the same way.At the 3rd day all rats were tested with maternal aggression,including mothers' following indices as total aggression times,biting times,pinning times,attack latency and duration of attack.Elevated plus maze (EPM) test was applied to analyze the behavioral changes.Results In terms of the duration of attack and attack latency,the indexes of group A and group D were significantly different from relevant data ((147.60±23.92) s and(79.70±9.88) s, P＜0.05), while other indexes had no difference(P＞0.05).The duration of attack and attack latency had a significant difference ((3.10±0.87) times, (13.60±5.14)times, (91.30±9.74)s and(167.20±30.02) s, P＜0.01) between group B and group D except total aggression times(P＞0.05).Group C and group D in given indexes had significant differences showing (6.40± 1.34) times, (15.10±4.35) times, (23.70±3.46) times, (49.80± 5.53) s and (215.60± 39.55) s (P＜0.01).Group A and group B in given indexes had significant differences (P＜ 0.05);and group B and group C had a significant difference (P＜0.01)except pinning times(P＞0.05).In EPM ,the open arm entry ratio and the open arm time ratio of both group A and group D were significantly different from respective percentage (0.47±0.13) and (0.13±0.05) (P＜0.01).The significant difference was found in group B and group D(P＜0.01);group A and group B had a statistical difference(P＜0.05);there was no difference in both groups in open arm time ratio(P＞0.05).Conclusion Oxytocin potentially mediates maternal aggression by attenuating stress, and improves the intimate bonding between mother and pups,which means dose dependency of OXT in this process.
ABSTRACT
Females are often less aggressive than males, but they exhibit high levels of agonistic behavior against an intruder in the area of the nest during lactation. This behavior is referred to as maternal aggression. In rats, maternal aggressive behavior occurs more often from postpartum day 3 (PPD 3) to PPD 12. Social instigation is an experimental protocol used to increase the levels of aggression that are typical of the species. In the present study we used social instigation to analyze the expression of a marker of neuronal activity, c-fos. Lactating rats on PPD 5, in the presence of their pups, were divided into four groups: (1) no social instigation and no aggressive behavior, (2) social instigation and no aggressive behavior, (3) no social instigation and aggressive behavior, and (4) social instigation and aggressive behavior. Sixty minutes after the aggression test we used immunohistochemistry to detect Fos in two brain regions, the ventral-orbital region of the prefrontal cortex (VO PFC) and dorsal raphe nucleus (DRN). Our results showed that rats with aggressive behavior that were provoked exhibited an increase in Fos expression in the VO PFC compared with the control group (i.e., no social instigation and no aggressive behavior). No change in Fos expression was found in the DRN. These results complement previous findings with microinjection of serotonin 5-hydroxytryptamine-1B receptor agonists into the same region, demonstrating that the VO PFC is an important region in the modulation of maternal aggressive behavior.