Abstract
In the brain nitric oxide (NO) is implicated in blood flow regulation, neurotransmitter release, learning and memory, neuronal plasticity, and neuronal degeneration and survival. To understand the role of NO in physiological as well as pathological conditions, it is essential to observe the dynamics of NO production itself. Using an NO-selective electrode system that allows the real-time in vivo measurement of NO, we examined changes in NO production during hypoxia and reoxygenation in the striatum of rats from late prenatal to adult stages. Under urethane anesthesia, an NO-selective electrode and laser Doppler flow probe was inserted into the striatum for measuring changes in NO concentration and tissue blood flow, respectively. In adult rats, spontaneous rhythmic production of NO ranging from about 0.2–1.5 Hz was observed, which was not related directly to cardiac or respiratory cycles. The rhythmicity in NO production was reduced after systemic administration of the NMDA channel blocker ketamine. In adult rats, brain hypoxia abolished the rhythmicity, but caused a large amount of NO production in the striatum. This overproduction of NO during hypoxia was also observed in the fetal and neonatal rat brain, although the basal rhythmic NO production was not detected. The immature rat brain may have less capacity to produce NO than the matured rat brain. The appearance of the rhythmic NO production in the brain may indicate the maturity of the brain NO-producing system. Further study is needed to clarify the origin of this rhythmic NO production in the rat brain. [J Physiol Sci. 2006;56 Suppl:S125]
