PARTURITION IN THE RABBIT IS COMPROMISED BY DAYTIME NURSING - THE ROLE OF OXYTOCIN

Rabbits nurse briefly only once each night and are frequently both pre gnant and lactating. To investigate the influence of the daily timing of nursing on parturition, does (n = 10 per group) were remated after giving birth and were allowed to nurse under one of three schedules: g roup 1 every 24 h in the light, group 2 every 24 h in the dark, and gr oup 3 at any time. Whereas does from groups 2 and 3 nursed and gave bi rth normally, does of group 1, forced to nurse out of phase with the n ormal schedule, showed disturbed nursing behavior and prolonged gestat ion followed by many stillbirths. In a second experiment, pregnant doe s (n = 10 per group) were treated daily either with oxytocin (OT) in t he light (group 4), with OT in the dark (group 5), or with progesteron e (P; group 6) or saline (group 7) in the light. All does gave birth n ormally except those of group 4, which responded similarly to group do es. These findings demonstrate that in the rabbit, parturition may be seriously compromised if does nurse out of phase with the normal sched ule and suggest that a shift in the daily timing of OT release may und erlie this.