Exposure to prenatal carbon monoxide and postnatal hyperthermia: Short andlong-term effects on neurochemicals and neuroglia in the developing brain

The effects of prenatal exposure to carbon monoxide (CO), a major component of cigarette smoke, was studied alone or in combination with postnatal hyp erthermia, on the structural and neurochemical development of the postnatal brain at 1 and 8 weeks. Pregnant guinea pigs (n = 11) were exposed to 200 p.p.m CO for 10 h/day from midgestation until term (68 days), whereas contr ol mothers (n = 10) breathed room air. On postnatal day 4, neonates from th e control and GO-exposed pregnancies were exposed to hyperthermia (35 degre es C) for 75 min or remained at ambient (23 degrees C) temperature. Using s emiquantitative immunohistochemical techniques the following neurotransmitt er alterations were found in the medulla at 1 week: a decrease in met-enkep halin-immunoreactivity (PR) following postnatal hyperthermia and an increas e in 5-hydroxytryptamine-IR following a combination of CO and hyperthermia. No alterations were observed in substance P- or tyrosine-hydroxylase-IR in any paradigm. At 8 weeks of age the combination of prenatal CO exposure fo llowed by a brief hyperthermic stress postnatally resulted in lesions throu ghout the brain and an increase in glial fibrillary acidic protein-IR in th e medulla, Such effects on brain development could be of relevance in cardi orespiratory control in the neonate and could have implications for the eti ology of Sudden Infant Death Syndrome, where smoking and hyperthermia are m ajor risk factors. (C) 2000 Academic Press.