EFFECT OF ETHER STRESS ON GROWTH-HORMONE DURING DEVELOPMENT IN THE NEONATAL RAT

Stress in adult rats causes an inhibition of growth hormone (GH) secretion which might be mediated by corticotropin-releasing factor (CRF). The response of neonates to stress differs from that observed in adults, including changes in GH secretion that are independent of CRF. The present study examines the effects of ether exposure, a stress known to elicit CRF release, on serum GH in the neonatal period. Preliminary experiments indicated that ether elicits increases in serum adrenocorticotropic hormone and corticosterone, and that the latter response is blocked by pretreatment with dexamethasone. Corticosterone was measured as an indicator of hypothalamo-pituitary-adrenal (HPA) axis stimulation for subsequent studies. Rat pups of 5, 8, 10, 15, 18 or 30 days were divided into three groups. Baseline animals were taken for decapitation directly from the mother. Ether animals were.exposed to ether fumes for 1 min, returned to the mother after a brief recovery period, and killed 30 min later. Handled control animals were removed from the mother briefly, returned, and similarly killed at 30 min. Blood was assayed for GH and corticosterone. Handling itself stimulated both GH and corticosterone on postnatal days 10 and 15 and suppressed GH and corticosterone on days 5 and 30. Ether significantly lowered GH and increased corticosterone when compared to this handling control from day 8 to 18, but values in ether-treated animals were different from baseline animals only at 5 and 30 days of age. These results indicate that ether stress produces a mild decrease in GH by day 5 postnatally and throughout the neonatal period which is only apparent in relation to 'handled' controls. Further, the handling involved in this procedure itself causes significant activation of the HPA axis and stimulation of GH secretion.