The effect of parturition on the interactions within pairs of common marmosets (Callithrix jacchus)

The relationship within common marmoset (Callithrix jacchus) pairs is based on pair-bond formation. This pair-bond is important for the successful rearing of the young and for the enhancement of reproductive success. Female marmosets bear twins which are carried mainly by males starting on the first day after the birth of the infants. Little is known, however, about the patterns of sociosexual interaction between callitrichid pairs and how these interactions change after the arrival of offspring. To evaluate the effect of parturition on these interactions, three heterosexual pairs of common marmosets were observed for four weeks before and four weeks after the birth of infants. The animals were kept in individual outdoor cages of the Nucleo de Primatologia, under environmental conditions. The time spent in proximity was mainly attributable to the initiative of females before parturition and the iniatiative of males after the offspring arrived. Males were groomed more before than after the birth of infants. In contrast, the amount of grooming received by females was the same in the two situations. These observations suggest that the relationship within pairs of common marmosets is slightly modified by the birth of infants and indicates that males and females could be using different strategies to enhance their reproductive success

Circadian variation of methyleugenol anesthesia in albino rats

In Wistar rats synchronized to a 12-h light/12-h dark cycle (lights on from 08:00 to 20:h), the ip injection of methyleugenol (200 mg/Kg) at 08:00, 12:00 and 16:00 h significantly increased the sleeping time (time between loss and recovery of righting reflex) when compared to animals anesthetized at 20:00, 24:00 and 04:00h. These data provide another example of the importance of circadian rhythms in biological systems and their practical relevance to pharmacology