The present research aimed to evaluate the role of 5-HT1A receptors in the modulation of maternal aggressive behavior and anxiety in female rats. Although, in a functional sense, parental aggression is a defensive protective behavior [1], the form and the topography of the behaviors displayed by a female rat with pups against a conspecific intruder share some similarities with the offensive behavior of males in colonies against subordinates and/or intruders. However, different from males, the aggressive behavior of lactating female rats comprises another strategy that is less contact-orientated which is characterized by the frontal attack (jump attack) directed to the head or snout of the intruder [2] and its form and topography have some similarities with the defensive explosive jump attack of a cornered rat by a predator.

8-OH-DPAT (0.2 µg/0.2 µl; 0.5 mg/0.2 ml and 2.0 µg/0.2 µl) was administrated locally into the median raphe nucleus (MRN) and into the medial septal nucleus (MS). We performed two experiments. In the first experiment, female Wistar rats, 60-90 days of age, were divided in groups according to the brain area studied: NMR (N=89); MS (N=88). The animals were maintained on a 12:12 light:dark cycle with the lights off at 16:30 hours and the experimental procedures were conducted during the dark phase, from 16:30 to 18:30 hours. The behaviors registered in the first experiment were: sniffing, locomotion, pup care, lateral threat, lateral attack, bite and frontal attack. The experiment was recorded on video tape. Afterwards, the tapes were coded by a trained observer, blind to the drug injected, using a special computer program. The mean frequency of the behaviors were compared among the groups by a factorial ANOVA and subsequently with Newman-Keuls Test (p<0.05). The results showed that in the NMR the 8-OH-DPAT in the dosage of 0.5 mg and 2.0 mg/0.2 ml decreased frontal attack, lateral attack and biting the intruder, attack and bite as compared to saline injection. In the MS the 8-OH-DPAT in the dose of 0.5 mg/0.2 ml increased the lateral attack and bite the intruder. In conclusion, the 5-HT agonist 8-OH-DPAT, when injected in the medial septum, has a excitatory effect on different components of maternal aggression. However, in median raphe nucleus this agonist has an inhibitory effect on maternal aggressive behavior of rats.

In the second experiment, virgin female rats (diestrus) were tested in the elevated plus maze. 8-OH-DPAT was administrated locally into the median raphe nucleus (N=83) and medial septal nucleus (N=91). The behaviors registered were frequency of scan and risk assessment. The percentage of time spent on open arm and closed arm were calculated. These behaviors were recorded. Afterwards, a trained observer, blind to the drug injected, recorded the behaviors using a special computer program. The mean frequency of the behaviors were compared among the groups by an ANOVA and subsequently by Newman-Keuls test (p<0.05). The results showed that the 5-HT1A receptor agonist 8-OH-DPAT in the median raphe nucleus (2.0 mg/0.2 ml) had an anxiolytic effect. However, in the medial septal nucleus (0.5 mg/0.2 ml) it increased anxiety.

References

1. Archer, J. (1988). The Behavioural Biology of Aggression. London: Cambridge University Press.
2. Lucion, A.B.; De Almeida, R.M.M. (1996). On the dual nature of maternal aggression in rats. Aggressive Behavior, 22, 365-373.