Abstract

The proposal is to carry out in vitro and in vivo studies to investigate central nervous system (CNS) plastic changes produced by anoxia/hypoxia occurring at birth. Interruption of oxygen availability implies depletion of NAD+ tissue stores; decrease of ATP formation; impairment of electron transport pumps, and anaerobic metabolism and acidosis. Upon re-oxygenation, there is a cascade of biochemical events, worsening the biological outcome by a deficient metabolism and/or imbalance produced by over-expression of alternative metabolic pathways. We propose that perinatal asphyxia long-term effects depend upon: (i) the extent of the hypoxic period; (ii) the maturity of the affected neurocircuitries; (iii) the extent of the metabolic imbalance released by the re-oxygenation period; (iv) changes in the expression of DNA repair-associated, sentinel proteins, including poly(ADP-ribose) polymerases (PARP). Excessive activation of PARP leads to prolonged NAD+ exhaustion and energy crisis, providing a mechanism for the hypothesis that perinatal asphyxia is a concurrent factor to the development of neurological and/or neuropsychiatric disorders with a clinical onset at late age stages Thus, the present proposal attempts to investigate on: (i) regional vulnerability of CNS neurocircuitries to perinatal asphyxia (focusing on axonal growth [GAP-43], synaptic targeting [synaptophysine], and monoamine, amino acids, and nitric oxide (NOS) neuronal phenotypes, studied with immunocytochemistry and neurochemistry [tissue/microdialysis]); (ii) regional and time-course changes in the expression and activity of sentinel enzymes, such as PARP (RT-PCR; Westernblot, immunocytochemistry; enzymatic assay); (iii) PARP inhibition as a potential strategy for neuroprotection against the metabolic imbalance and cell death triggered by perinatal asphyxia. The effect of nicotinamide on the above parameters will be investigated, using this drug as a lead for other PARP-inhibitors. The substituted benzamide N-(1-Ethyl-2-pyrrolidinylmethyl)-2-methoxy-5- sulphamoyl benzamide; and the xanthines analogs, 1,3-dimethylxanthine and 1,7-dimethylxanthine will first be studied in vitro (PARP activity enzymatic assay), before attempting any in vivo strategy. It is expected that the present proposal will allow identifying critical molecular, morphological, physiological and pharmacological parameters, to be considered when planning neonatal care and development programmes.