Objective: Therapeutic hypothermia (HT) is the standard treatment for newborns after perinatal asphyxia. Preclinical studies report that HT is more effective when started early. Methods: Eighty cooled newborns were analyzed and grouped according to when cooling was started after birth: early (≤180 min) or late (>181 min). For survivors we analyzed whether starting cooling early was associated with a better psychomotor or mental developmental index (PDI or MDI, Bayley Scales of Infant Development II) than late cooling. Results: Forty-three newborns started cooling early and 37 started late. There was no significant difference in the severity markers of perinatal asphyxia between the groups; however, nonsurvivors (n = 15) suffered more severe asphyxia and had significantly lower centiles for weight (BWC; p = 0.009). Of the 65 infants that survived, 35 were cooled early and 30 were cooled late. There was no difference in time to start cooling between those who survived and those who did not. For survivors, median PDI (IQR) was significantly higher when cooled early [90 (77-99)] compared to being cooled later [78 (70-90); p = 0.033]. There was no increase in cardiovascular adverse effects in those cooled early. There was no significant difference in MDI between early and late cooling [93 (77-103) vs. 89 (76-106), p = 0.594]. Conclusion: Starting cooling before 3 h of age in surviving asphyxiated newborns is safe and significantly improves motor outcome. Cooling should be initiated as soon as possible after birth in eligible infants.

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We investigated the expression of metabotropic glutamate receptor (mGluR) isoforms in CG-4 rodent oligodendroglial progenitor cells (OPC) and rat brain oligodendrocytes. Our RT-PCR analysis detected mRNAs for mGluR3 and mGluR5 isoforms in OPCs. Although neurons express both mGluR5a and mGluR5b splice variants, only mGluR5a was identified in OPCs. Antibodies to mGluR2/3 and mGluR5 detected the corresponding receptor proteins in immunoblots of OPC membrane fractions. Furthermore, immunocytochemical analysis identified mGluR5 in oligodendrocyte marker O4-positive OPCs. The expression of mGluR5 was also demonstrated in oligodendrocyte marker (O4 and O1) positive cells in white matter of postnatal 4-and 7-day-old rat brain sections using immunofluorescent double labelling and confocal microscopy. The mGluR5 receptor function was assessed in CG-4OPCs with fura-2 microfluorometry. Application of the mGluR1/5 specific agonist (S)-3,5-dihydroxyphenylglycine (DHPG) induced calcium oscillations, which were inhibited by the selective mGluR5 antagonist 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP). The DHPG induced calcium oscillations required Ca 2+ release from intracellular stores. InOPCs the group II mGluR agonist (2S,2¢R,3¢R)-2-(2¢,3¢-dicarboxycyclopropyl)glycine (DCG-IV) decreased forskolin-stimulated cAMP synthesis, indicating the presence of functional mGluR3. The newly identified mGluR3 and mGluR5a may be involved in the differentiation of oligodendrocytes, myelination and the development of white matter damage. Glutamate is the major excitatory neurotransmitter in the CNS and its responses are mediated by ionotropic (iGluRs) and metabotropic (mGluRs) glutamate receptors. The iGluRs mediate fast synaptic transmission and the mGluRs are involved in a variety of modulatory events associated with neuronal activity. The iGluRs are multimeric, cation-specific ion channels that are classified into three families on the basis of their pharmacology, electrophysiology and sequence homology: namely the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate, and N-methyl-D-aspartate (NMDA) receptors (Dingledine et al. 1999). The mGluRs are G-protein coupled receptors, which mediate relatively slow responses to glutamate. There are eight mGluR genes (mGluR1-8) and these have been divided into three groups based on pharmacological, signal transduction and sequence similarities. Group I comprises mGluR1 and mGluR5, which are involved in the mobilization of intracellular calcium by stimulating phospholipase C and are activated by (S)-3,5-dihydroxyphenylglycine (DHPG). In group II, the mGluR2 and mGluR3 are typically linked to inhibition of adenylyl cyclase (AC) and react effectively with (2S,1¢S,2¢S)-2-(carboxycyclopropyl)glycine (DCG-IV). In group III, the mGluR4, mGluR6, mGluR7 and mGluR8 are linked to inhibition of cAMP formation by AC and respond effectively to L-2-amino-4-phosphonobutyrate (Conn and Pin 1997;Schoepp et al. 1999). Oligodendrocytes are responsible for axon myelination and they a...

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GABA B receptors (GABA B Rs) are involved in early events during neuronal development. The presence of GABA B Rs in developing oligodendrocytes has not been established. Using immunofluorescent co-localization, we have identified GA-BA B R proteins in O4 marker-positive oligodendrocyte precursor cells (OPCs) in 4-day-old mouse brain periventricular white matter. In culture, OPCs, differentiated oligodendrocytes (DOs) and type 2 astrocytes (ASTs) express both the GABA B1abcdf and GABA B2 subunits of the GABA B R. Using semiquantitative PCR analysis with GABA B R isoform-selective primers we found that the expression level of GABA B1abd was substantially higher in OPCs or ASTs than in DOs. In contrast, the GABA B2 isoform showed a similar level of expression in OPCs and DOs, and a significantly higher level in ASTs. This indicates that the expression of GABA B1 and GABA B2 subunits are under independent control during oligodendroglial development. Activation of GABA B Rs using the selective agonist baclofen demonstrated that these receptors are functionally active and negatively coupled to adenylyl cyclase. Manipulation of GABA B R activity had no effect on OPC migration in a conventional agarose drop assay, whereas baclofen significantly increased OPC migration in a more sensitive transwell microchamber-based assay. Exposure of cultured OPCs to baclofen increased their proliferation, providing evidence for a functional role of GABA B Rs in oligodendrocyte development. The presence of GABA B Rs in developing oligodendrocytes provides a new mechanism for neuronal-glial interactions during development and may offer a novel target for promoting remyelination following white matter injury.

Oligodendrocytes (OLs) are responsible for axon myelination and are the principal cells targeted in preterm white matter injury. The cellular and molecular mechanisms involved in white matter development and immature OL injury are incompletely understood. Metabotropic glutamate receptors (mGluRs) modulate neuronal development and survival, and have recently been identified in oligodendrocyte progenitor cells (OPCs). Using the highly homogeneous CG-4 OPC line and O4 marker-immunoselected primary OLs, we established the differentiation stage-specific expression profile of mGluR3 and mGluR5 mRNAs and proteins in the oligodendroglial lineage and type-2-astrocytes (ASTs). Our quantitative analysis indicated no changes in mGluR3, but a significant downregulation of mGluR5a mRNA and protein expression during differentiation of OPCs into OLs or ASTs. The down-regulation of mGluR5a had functional consequences, with significantly fewer OLs and ASTs than OPCs responding to the group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine with intracellular Ca 2+ concentration oscillations. Neither stimulation nor inhibition of mGluR3 or mGluR5 altered OPC migration, suggesting that these receptors do not play prominent roles in the regulation of OPC motility. The activation of mGluR5 completely protected OPCs and substantially reduced staurosporine-induced apoptosis in OLs. This suggests that the down-regulation of mGluR5 in premyelinating OLs is likely to contribute to their increased vulnerability, and that the targeting of mGluR5 may be a potential therapeutic strategy for future development.

BackgroundProgressive ventricular dilatation after intraventricular haemorrhage (IVH) in preterm infants has a very high risk of severe disability and death. Drainage, irrigation and fibrinolytic therapy (DRIFT), in a randomised controlled trial (RCT), reduced severe cognitive impairment at 2 years.ObjectiveTo assess if the cognitive advantage of DRIFT seen at 2 years persisted until school age.ParticipantsThe RCT conducted in four centres recruited 77 preterm infants with IVH and progressive ventricular enlargement over specified measurements. Follow-up was at 10 years of age.InterventionIntraventricular injection of a fibrinolytic followed by continuous lavage, until the drainage was clear, and standard care consisting of control of expansion by lumbar punctures and if expansion persisted via a ventricular access device.Primary outcomeCognitive quotient (CQ), derived from the British Ability Scales and Bayley III Scales, and survival without severe cognitive disability.ResultsOf the 77 children randomised, 12 died, 2 could not be traced, 10 did not respond and 1 declined at 10-year follow-up. 28 in the DRIFT group and 24 in the standard treatment group were assessed by examiners blinded to the intervention. The mean CQ score was 69.3 (SD=30.1) in the DRIFT group and 53.7 (SD=35.7) in the standard treatment group (unadjusted p=0.1; adjusted p=0.01, after adjustment for the prespecified variables sex, birth weight and IVH grade). Survival without severe cognitive disability was 66% in the DRIFT group and 35% in the standard treatment group (unadjusted p=0.019; adjusted p=0.003).ConclusionDRIFT is the first intervention for posthaemorrhagic ventricular dilatation to objectively demonstrate sustained cognitive improvement.Trial registration numberISRCTN80286058.