The stress of being restrained reduces brain damage after a hypoxic-ischaemic insult in the 7-day-old rat.

Experimental animals and patients are immobilized to allow continuous monitoring of physiological parameters. Restraint stress affects brain neurotransmitter levels and induces expression of immediate early genes. Whether immobilization stress affects outcomes in newborn animals which have suffered a hypoxic-ischaemic insult is unknown. Twenty 7-day-old rats subjected to unilateral carotid ligation followed by 2 h hypoxia were randomly assigned to carry a rectal probe or to move freely. The 10 restrained animals showed 50% reduction in damage in all brain regions (p < 0.0.3). Plasma lactate levels, a marker of stress, were three times higher in animals carrying a rectal probe (p < 0.0.02) than those moving freely. We conclude that the stress of being restrained reduced damage after a hypoxic-ischaemic insult in the immature rat.