The influence of NO-containing ruthenium complexes on mouse hippocampal evoked potentials in vitro

The influence of different, nitric oxide-containing ruthenium complexes on the evoked potentials recorded from the CA1 region of the mouse hippocampus in vitro has been investigated. Of the compounds tested, only trans-[(NO)( P(OEt)(3))(NH3)(4)Ru](PF6)(3) (1-2.5 mM) exerted a strong facilitatory acti on on the population spike, the EPSP, and the spontaneous activity. Its act ivity probably depends upon its ability to release NO following reduction. The phosphito ligand is important both in terms of adjusting the reduction potential of the complex to be biologically accessible and in labilizing th e coordinated NO. The effects of this compound could not be reversed by per fusion. Scavenging NO in slices preincubated with oxyhemoglobin prior to th e addition of this compound eliminated its neurophysiological effects. The control molecules trans-[(P(OEt)(3))(2)(NH3)(4)Ru] (PF6)(2), trans-[(H2O)(P (OEt)(3)) (NH3)(4)Ru](PF6)(3), and [(NO)(NH3)(5)Ru]Cl-3, which are structur ally similar, but unable to generate NO, were ineffective. NaNO2 suppressed neuronal firing. Attempts to induce Long-Term Potentiation (LTP) at the ti me of maximal effect of trans- [(NO)(P(OEt)(3))(NH3)(4)Ru](PF6)(3), were un successful, suggesting that the mechanism of amplification induced by trans -[(NO)(P(OEt)(3))(NH3)(4)Ru](PF6)(3) and LTP may share common pathways. (C) 2001 Elsevier Science Inc. All rights reserved.