The effects of mother-infant separation upon nursing and suckling behaviors of the rat

Abstract

The present study was intended to evaluate the hypothesis that the nursing-suckling relationship of rats proceeds from the mother-leading-type in early postpartum days to the infants-leading-type in later postpartum. Four groups were organized to make tests on the effects of different kinds of mother-infant separation (8-hr) upon nursing-suckling behaviors. Groups were Groups MIS (a separated mother and infants group), MS (mother-separated and infants-fostered group), IS (a foster-mother and separated-infants group), and C (non-separated control group). The separation of each group, lasting for 8-hr, was made at 1-2, 6-7, 11-12, 16-17, 21-22, 26-27, and 31-32 days after parturition. In Exp. I, nursing behavior of mother and suckling and/or eating behavior of infants in mother-infant interactions were observed by time-sampling method for 30 min following 8-hr of separation. In Exp. II, the suckling test of infants (half of the litter) was made on the anesthetized mother at the presence of food pellets. The results of Exp. I showed that nursing-suckling episodes were more frequent in Groups MIS, MS, and IS than in Group C (fig. 1). Further, the differences among the first three groups were not significant before 11-12 days of age. However, the infant-separated group (Group IS) showed higher level of response at 16-17, 21-22 days of age, suggesting the active role of infants in starting nursing-suckling episodes at these ages.(ABSTRACT TRUNCATED AT 250 WORDS)