Figure 3.

Plasma melatonin concentration during an episode of acute hypoxia. Thirty minutes before taking the normoxia₁ blood sample, five newborn lambs received an i.v., bolus of vehicle (1 ml 10% ethanol-saline, white circles) and six i.v., bolus of melatonin (0.27 mg kg⁻¹ in 1 ml of vehicle, black circles). Arrows indicate time of bolus (V, vehicle; M, melatonin). Values are means ± SEM. Significant differences, P < 0.05: a, melatonin group vs. vehicle group in the same time periods.