Epidemiological observations raised the possibility that coffee was deleterious for newborn babies. For the last ten years the American Food and Drug Administration (FDA) has therefore recommended that pregnant women limit their consumption of coffee.
The first underlying cerebral mechanisms have just been elucidated, by the use of a particular animal model, by INSERM unit 29.
The researchers based their investigations on two observations. First, caffeine contained in the coffee drunk by mothers crosses the fetal blood-brain barrier. On arriving in the brain, the caffeine binds specifically to neuronal adenosine receptors.
Second, fetal oxygenation frequently declines during delivery, especially when contractions last a few minutes, with a risk of hypoxia and severe complications.
It is these two phenomena (caffeine and oxygen starvation) that the researchers reproduced on neurons of the hippocampus, a particular brain structure that appears to be the site of memorization processes. In the presence of caffeine at a concentration equivalent to a few cups of coffee, and in the absence of oxygen (for 3-4 minutes), nerve cells in the hippocampus showed paroxystic electrical activity: in other words, they all fired at the same time, as during epileptic fits. Nothing happened if caffeine was not added to the preparation. Moreover, in the presence of oxygen, caffeine alone failed to produce such neuronal activity. It is therefore the combination of these two factors that induces fits.
Schematically, the caffeine molecule binds to adenosine receptors, thereby blocking the action of adenosine, the endogenous neuromediator, which plays an important role in handling stress. During stressful episodes such as oxygen starvation, adenosine protects the nerve circuits from uncontrolled excitation, which can be detrimental. Caffeine takes the place of adenosine and prevents it from playing its normal role.
This experiment illustrates the detrimental
Contact: Marie Christine Simon
French National Institute for Health and Medical Research (INSERM)