EFFECT OF THE PRENATAL MATERNAL ENVIRONMENT ON THE CONTROL OF BREATHING DURING NON-RAPID-EYE-MOVEMENT SLEEP IN THE DEVELOPING LAMB

This study examines the effects of altering the prenatal maternal meta bolic and hormonal environment via chronic cold exposure of under-fed ewes on developmental changes in breathing control of developing lambs . Breathing frequency and timing were measured during non rapid-eye-mo vement (non-REM) sleep in lambs born from either shorn or unshorn ewes after being maintained for at least one hour at warm (28-19-degrees-C ) and cool (14-5-degrees-C) ambient temperatures at 1, 4, 14 and 30 da ys of age. Breathing frequency and oxygen consumption were significant ly higher in 1 day old lambs born from shorn ewes compared with those lambs born from unshorn ewes, at both warm and cool ambient temperatur es. In the shorn group breathing frequency decreased between 1 and 4 d ays of age and continued decreasing upto 30 days of age, during which period inspiratory and to a greater extent expiratory time, lengthened . Laryngeal ''braking'' of expiratory airflow was observed in more tha n 50% of lambs born from shorn ewes during non-REM sleep in the warm a t 4, 14 and 30 days of age, and in the cold at 14 and 30 days of age. In contrast, lambs born from unshorn ewes showed no change in breathin g frequency between 1 and 4 days of age, but a decrease was observed b etween 4 and 14 days of age, whilst laryngeal ''braking'' of expirator y airflow was rarely observed at any age. It is concluded that the dev elopment of breathing control over the first month of postnatal life c an be affected by alterations in the fetal environment elicited by chr onic cold exposure of the mother.