MELBOURNE, Australia (Reuters Health) Jul 10 - Research in lambs has led Australian researchers to propose a link between the neurosteroid allopregnanolone and sudden infant death syndrome (SIDS) in infants. The research was carried out by Monash University physiology PhD student Saraid Billiards.

Based on observations that SIDS is linked to infection and hypoxia, Billiards, in conjunction with her supervisors Dr. David Walker and Dr. Jonathan Hirst, injected newborn lambs with low levels of E. coli bacterial endotoxin. Billiards stressed that the infection mild and not severe enough to cause septicaemia.

"Not only did the lambs' amount of sleep increase dramatically" after infection, she said, "but so did the neurosteroid allopregnanolone. It increased in both the brain and plasma, but in the brain it increased dramatically. Why this is so exciting is that allopregnanolone has sedative and anaesthetic properties."

Billiards said that the team is proposing that the increased sleep as a result of infection is due to the increase in production of allopregnanolone.

Billiards explained "we've taken that one step further and looked at the effect of hypoxia, which is almost certain to be involved in SIDS. Hypoxia alone increased the concentration of allopregnanolone in the brain, and when we combined hypoxia with infection, it just went crazy--it went through the roof."

She said that this gave the team more confidence in suggesting that babies with an underlying infection, who are further challenged by a hypoxic event, are sedated to such a degree that the hypoxia challenge does not waken them and they die.

Not only did the lambs increase their amount of sleep, said Billiards, they were unresponsive in terms of feeding, and unaware of what was going on around them.

"Next year," she told Reuters Health, "we hope to have access to samples from babies who have died from SIDS so we can assess the concentrations of allopregnanolone, to see if they are elevated. If they are, the next step will be to look at preventative measures." Billiards added that neurosteroid blockers, such as trilostane, which blocks the enzyme that produces allopregnanolone, have been shown in the Monash University laboratory to reduce the amount of time lamb foetuses sleep.

The research is to be published in the journal Paediatric Research later this year.