Effect of neonatal dexamethasone exposure on growth and neurological development in the adult rat

Abstract

Neal, Charles R., Jr., Gabrielle Weidemann, Mohamed Kabbaj, and Delia M. Vázquez. Effect of neonatal dexamethasone exposure on growth and neurological development in the adult rat. Am J Physiol Regul Integr Comp Physiol 287: R375-R385, 2004. First published April 29, 2004; 10.1152/ajpregu.00012.2004.-Until recently, the synthetic glucocorticoid dexamethasone was commonly used to lessen the morbidity of chronic lung disease in premature infants. This practice diminished as dexamethasone use was linked to an increased incidence of cerebral palsy and short-term neurodevelopmental delay. Of more concern is the fact that we know little regarding dexamethasone effects on long-term neurodevelopment. To study the effects of neonatal dexamethasone exposure on long-term neurodevelopment, we have developed a rat model where newborn pups are exposed to tapering doses of dexamethasone at time points corresponding to the neurodevelopmental age when human infants are traditionally exposed to this drug in the neonatal intensive care unit. Using a within-litter design, pups were assigned to one of three groups on postnatal day 2 (P2): handled controls, saline-injected controls, and animals receiving intramuscular dexamethasone between P3 and P6. Somatic growth was decreased in dexamethasone-treated animals. Dexamethasone-treated animals demonstrated slight delays in indexes of neurodevelopment and physical maturation at P7 and P14, but not P20. In adolescence (P45), there was no difference between groups in an open field test. However, as adult dexamethasone-treated animals were less active in the open field and spent more time in closed arms of the elevated plus maze. The serum corticosterone response to crowding stress in dexamethasone-treated animals was no different from controls, but they demonstrate a delay in return of corticosterone levels to baseline. These differences in behavior and hormonal stress responsiveness suggest that neonatal dexamethasone exposure may permanently alter function of the neuroendocrine stress axis. steroids; prematurity; brain; corticosterone; limbic-hypothalamicpituitary-adrenal axis SEVERE RESPIRATORY DISTRESS syndrome is commonly experienced in extremely low birth weight (ELBW) infants, resulting in various degrees of ventilator and/or oxygen dependency and subsequent onset of chronic lung disease (CLD). Until recently, administration of a prolonged course of postnatal dexamethasone to ELBW infants was frequently practiced in an attempt to lessen the progression of CLD. Although clinical trials using dexamethasone in this fashion failed to consistently demonstrate improvement in mortality or length of hospitalization, exposures of up to 42 days were commonly used in many neonatal units (4,8,17,55,56). A recent study examining the outcome of ELBW infants (birth weight between 500 and 750 g) found that 43% of those infants born from 1990 to 1992 received dexamethasone compared with 84% of ELBW infants born between 1993 and 1995 (40). Routine use of dexamethasone continued until Yeh and colleag...

Neuroprotective effect of magnesium sulfate and dexamethasone on intrauterine ischemia in the fetal rat brain: ultrastructural evaluation

“…Thus, it has been long believed that, with dexamethasone treatment, the structural and functional integrity of biological membranes can be preserved (3,15). The primary mechanism of the neuroprotective effect of dexamethasone is the inhibition of lipid peroxidation (4,5,15). In our work, dexamethasone decreased the TBARS values back to control levels and decreased the mitochondrial damage when compared to ischemic brain injury group.…”

“…Dexamethasone has demonstrated a beneficial inhibition of lipid peroxidation and neuroprotective effects (4,5,15). The dexamethasone exerts a series of effects on injured neural tissue (13,20).…”

“…These effects are the regulation of energy metabolism, the prevention of progressive posttraumatic ischemia, the prevention of neurofilament degradation and the inhibition of membrane lipid hydrolysis (3,4,25). Thus, it has been long believed that, with dexamethasone treatment, the structural and functional integrity of biological membranes can be preserved (3,15). The primary mechanism of the neuroprotective effect of dexamethasone is the inhibition of lipid peroxidation (4,5,15).…”

Glucocorticoids exacerbate hypoxia-induced expression of the pro-apoptotic gene Bnip3 in the developing cortex

“…Postnatal DEX treatment decreases both the number and size of cortical neurons (Kreider et al, 2006), which persists into adulthood as these rats show altered social behavior and learning and memory deficits (Kamphuis et al, 2004, Neal et al, 2004.…”

Dexamethasone but not the equivalent doses of hydrocortisone induces neurotoxicity in neonatal rat brain

“…Animal studies have also demonstrated that Dex impairs brain function, fetal growth, and neurodevelopment (3,4). These concerns have highlighted the need to find a safer alternative to Dex for the treatment of CLD.…”