Models in Immature Animals

It is generally accepted that neurons in the immature brain tolerate a longer period of oxygen deprivation and/ or ischemia than those in the adult (Towfighi et al., 1997). However, there are conflicting reports, showing that the immature brain is less resistant to hypoxic-ischemic brain damage than its adult counterpart (Yager et al., 1996). This is supported by other studies after HI or excitotoxic injury (McDonald et al., 1988; Ikonomidou et al., 1989; Marret et al., 1995). Furthermore, clinical data suggest that outcome and mortality after acute brain injury are age-dependent, with more severe injuries in infants than in adults (Adelson and Kochanek, 1998).

Precise correlations with human brain development are difficult, in particular because of the fact that rodents present an arrhinencephalic brain. However, brains of 7-day-old rats and 10-day-old mice are similar to third-trimester (34 to 35 weeks of gestation) human fetuses (and thus premature human newborns), in terms of cellular proliferation, cortical organization, synapse number, neurochemical indices such as neurotransmitter synthetic enzymes, and electrophysiology (Hagberg et al., 1994; Marret et al., 1995). Cortex of the 10- to 12-day-old rats (18-35 g) could correspond to term newborn with myelination of the fiber tract beginning on approximately day 11 in the rat (Rice et al., 1981). Based on these considerations, postnatal day 1 (P1) could be equivalent to 18 to 20 weeks gestation and P3 of 24 to 28 weeks gestation in humans.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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