OVULATORY DELAY ALTERS POSTNATAL-GROWTH, BEHAVIOR, AND BRAIN STRUCTURE IN RATS

To investigate the effect of a delay in ovulation on postnatal growth and development in resultant rat offspring, a 1-day ovulatory delay wa s induced by sodium pentobarbital, animals mated, and the offspring mo nitored. There were no differences between control and 1-day delayed o ffspring in the number of live or dead births, number of males or fema les, nor in the ratio of sexes. Delayed pups had a slightly lower birt h weight, but then recovered to weigh more than controls by day 12. In the first two weeks post-parturition, delayed pups displayed an earli er ability to reorient themselves in a negative geotaxis test, but no differences by the righting reflex and reflex suspension tests. At pos tnatal day (pnd) 28, delayed pups exhibited decreased activity in a co ntinuous corridor test, but no alterations in gait. At this time, the brains of delayed animals revealed thickening of cortical layers V plu s VI. There were significant correlations between various developmenta l endpoints (body weight, negative geotaxis, continuous corridor activ ity, and gait) and the cortical layer thicknesses. The results indicat e that ovulatory delay produces changes in brain cortical thickness, w ith correlative changes in growth and behavior. Although the mechanism s by which ovulatory delay alters postnatal development and brain stru cture are unknown, ovulatory delay may alter the uterine environment d uring early pregnancy. (C) 1998 Elsevier Science B.V.