Induction of proinflammatory cytokines has been proposed to be a link between prenatal maternal intrauterine infection and neonatal brain damage. It is known that the endotoxin, lipopolysaccharide (LPS), released during bacterial infection crosses the placenta. Cytokine induction in the fetal rat brain after maternal administration of LPS was determined by reverse transcriptase-polymerase chain reaction method. LPS suspension in pyrogen-free saline was administered (i.p.) to pregnant rats at 18 d of gestation. The control group was treated with pyrogen-free saline. Expression of the proinflammatory cytokines, tumor necrosis factor-alpha and IL-1beta mRNA, in the fetal rat brain was increased in a dose-dependent manner at 1 h after LPS administration. The great increase in expression of IL-1beta mRNA was only observed at 1 h after injection of LPS (4 mg/kg), whereas the increased expression of tumor necrosis factor-alpha was still detectable from 4 to 24 h after LPS administration. Brain injuries were examined by immunohistochemistry in 8-d-old rat pups born to the dams that were consecutively treated with LPS (500 microg/kg) or pyrogen-free saline on gestation d 18 and 19. No apparent necrotic tissue damage was found in either the LPS group or the control group. Myelin basic protein staining, as a marker of myelin, was clearly observed in the internal capsule and the fimbria hippocampus in the rat brain from the control group. Myelin basic protein staining was much less and weaker in the brains of the LPS-treated group. Glial fibrillary acidic protein-positive astrocytes were observed in both the control and the LPS-treated groups. The LPS-treated group appeared to have more glial fibrillary acidic protein-positive astrocytes in the hippocampal and the cortex areas of the brain than the control group. Immunoblotting data showed that glial fibrillary acidic protein content in the cortex or the hippocampus of the LPS-treated rat brain was higher than in the control group. OX-42-positive staining (a marker of the type 3 complement receptors) of microglial cells was greatly reduced in the 8-d-old rat brain after maternal LPS administration. However, histochemistry with tomato lectin showed that staining of both amoeboid and ramified microglial cells in the LPS-treated rat brain was similar to that in the control group. The overall results indicate that maternal LPS administration induces an increased expression of IL-1beta and tumor necrosis factor-alpha mRNA in the fetal brain. Maternal LPS administration also increases glial fibrillary acidic protein-positive astrocytes, decreases myelin basic protein and alters immunoreactivity of microglia in the brain of offspring. Although results from the current study do not provide direct evidence linking LPS-induced cytokines with the abnormalities in the neonatal rat brain, our animal model may be appropriate for exploring the mechanisms involved in the effects of maternal infection on glial cells in the brains of offspring.

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Serotonin (5-HT) plays a key role in early brain development, and manipulation of 5-HT levels during this period can have lasting neurobiological and behavioral consequences. It is unclear how perinatal exposure to drugs, such as selective serotonin reuptake inhibitors (SSRIs), impacts cortical neural network function and what mechanism(s) may elicit the disruption of normal neuronal connections/interactions. In this article, we report on cortical wiring organization after pre-and postnatal exposure to the SSRI citalopram. We show that manipulation of 5-HT during early development in both in vitro and in vivo models disturbs characteristic chemoarchitectural and electrophysiological brain features, including changes in raphe and callosal connections, sensory processing, and myelin sheath formation. Also, drug-exposed rat pups exhibit neophobia and disrupted juvenile play behavior. These findings indicate that 5-HT homeostasis is required for proper brain maturation and that fetal/infant exposure to SSRIs should be examined in humans, particularly those with developmental dysfunction, such as autism.S erotonin (5-HT) has long been postulated to play a trophic role in brain morphogenesis, including cell proliferation, migration, and differentiation. It is also known to be one of the first neurotransmitters to appear in the central nervous system (1, 2). An obvious question that can be raised relates to whether perinatal exposure to antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), can affect cortical circuit development and function. Perhaps one of the most intriguing previous findings related to 5-HT and early cortical organization was the observation from immunohistochemical and 5-HT transporter (SERT) binding studies that, at postnatal days 2-14 (P2-P14), rodent primary sensory cortex (notably layer IV of visual, auditory, and somatosensory areas) is transiently innervated by aggregates of fine grainlooking 5-HT-containing processes (3)(4)(5). Surprisingly, it became clear that, in early brain development, 5-HT is taken up into glutamatergic thalamocortical terminals (6, 7) and used in combination with the 5-HT 1B receptor on layer IV afferents (8). At present, the functional implication of such transient 5-HT expression and targeting, namely the primary sensory thalamocortical afferents during early development, remains unknown.5-HT and Abnormal Brain Development. Interestingly, manipulations of rodent brain 5-HT levels during early development, either through increases (produced in SERT or monoamine oxidase knockout mice) or decreases (produced by parachlorophenylalanine or other treatments), have been shown to produce the downstream effect of interfering with the formation of the whisker (barrel) representation in the primary somatosensory cortex and promoting aggressive and/or anxiety-related behaviors (9-14). Furthermore, early-life modification of 5-HT levels has been shown to cause overreaction to auditory or tactile sensory stimulation (15) and abnormal response properties of cor...

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