Maternal Care Received by Individual Pups Correlates with Adult CA1 Dendritic Morphology and Synaptic Plasticity in a Sex-Dependent Manner

Maternal care is an important environmental factor for rats early in life. Adult offspring from dams exhibiting extremely high versus low maternal care differ remarkably in dendritic complexity and long-term synaptic potentiation in the CA1 area. However, > 70% of the pups do not belong to these extreme categories of maternal care, questioning the general relevance of these observations. Therefore, the present study investigated whether the influence of maternal care is discernable over its entire range and can serve as an index predicting later CA1 structure and function. The amount of licking and grooming (%LG) received was determined for each pup during the first postnatal week. In males, both total apical branch length and dendritic complexity correlated significantly and positively with %LG. In females, we observed a nonsignificant negative correlation, also when controlled for variations in oestradiol and progesterone levels. The correlation in females was significantly different from that in males. No significant correlation was observed between the %LG and the amount of synaptic potentiation, either in male or in female offspring, regardless of whether slices had been treated with corticosterone or vehicle. However, in male rats, the degree of potentiation seen after corticosterone compared to vehicle treatment was almost significantly related to the %LG received early in life; this differed significantly from that observed in females. The data from the present study suggest that %LG received early in life results in mild, yet sex-dependent effects on adult CA1 structure and function.