| Summary: | 碩士 === 國立陽明大學 === 生理學研究所 === 89 === Age-related changes of sensitivity to hypoxia and inhibitory modulation of nitric oxide during hypoxia in rat locus coeruleus neurons were investigated by intracellular recording from in vitro brain slices.
(1) Age-related changes of sensitivity to hypoxia: In response to a brief exposure to hypoxic medium, equilibrated with 95%N2-5%CO2, two populations of cells could be distinguished, typeⅠneuron(n=12, 66.7%) showing hyperpolarization and cessation of spontaneous action potentials, and typeⅡneurons(n=6, 33.3%) displaying gradual pure depolarization, instead of hypoxic hyperpolarization. With longer exposure to hypoxic solution, both types of neuron showed a gradual depolarization. The results showed that the latencies of resting membrane potential depolarize to a level 20mV more positive than the pre-hypoxic resting potential were decreased with age (typeⅠ:n=5. typeⅡ:n=4, p<0.05). The locus coeruleus neurons in immature rats showed greater resistance to oxygen lack than the older rats.
(2) Inhibitory modulation of nitric oxide during hypoxia: The latencies of resting membrane potential depolarize to a level 40 mV more positive than the pre-hypoxic resting potential were decreased by iNOS(inducible nitric oxide synthase) inhibitor, aminoguanidine, application from 20.2min(typeⅠneuron, n=2) and 27.5min(typeⅡneuron, n=3)under control conditions to 17min(typeⅠneuron, n=3) and 16.8min(typeⅡneuron, n=2) with iNOS inhibitor(p<0.05). These results demonstrate a neuroprotective effect of nitric oxide on locus coeruleus neurons.
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