Ischemia-induced taurine release is modified by nitric oxide-generating compounds in slices from the developing and adult mouse hippocampus.
The novel neurotransmitter/neuromodulator nitric oxide (NO), which is linked to the activation of the N-methyl-D-aspartate class of glutamate receptors, has been shown to modify transmitter release in brain tissue. Release of the inhibitory amino acid taurine is also markedly enhanced by N-methyl-D-aspartate and NO-producing agents under normal conditions in the mouse hippocampus. The release of preloaded [3H]taurine from hippocampal slices from adult (3-month-old) and developing (7-day-old) mice was characterized under ischemic conditions in the presence of different NO-generating compounds, hydroxylamine, sodium nitroprusside, and S-nitroso-N-acetylpenicillamine (SNAP), using a superfusion system. The ischemia-induced taurine release at both ages was markedly enhanced by 1.0 mM nitroprusside and 1.0 mM SNAP, whereas 5.0 mM hydroxylamine was effective only in adults. The nitroprusside- and SNAP-induced releases were reduced by the inhibitors of NO synthase (nitroarginine and 7-nitroindazole) and NO-sensitive soluble guanylyl cyclase [1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one], suggesting involvement of the NO/cGMP pathway. The release in ischemia in the absence of Na+ was modified by NO compounds only in adults; the 0.1 mM N-methyl-D-aspartate stimulated taurine release at both ages. The enhanced release of taurine associated with NO production could be beneficial to brain tissue under cell-damaging conditions and corroborates the neuroprotective role of this amino acid, particularly in the immature brain.
Saransaari
Pirjo
P
Tampere Brain Research Center, Medical School, University of Tampere, Finland. blpisa@uta.fi
Oja
Simo S
SS
D000367:Age Factors; D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D006624:Hippocampus / Q000098:blood supply / Q000254:growth & development / Q000378:metabolism*; D066298:In Vitro Techniques; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis*; D020030:Nitric Oxide Donors / Q000378:metabolism*; D013654:Taurine / Q000378:metabolism*
D020030:Nitric Oxide Donors; D013654:Taurine; D009569:Nitric Oxide