An electrochemical microprobe for detecting nitric oxide release in brain tissue.

To detect the release of nitric oxide (NO) in brain tissue, an electrochemical microprobe was developed. The output current of the probe correlated linearly with the NO concentration at the tip, and the sensitivity of the probe was between 3.5 and 106 pA per 1 microM change in NO concentration. This probe showed no sensitivity to oxygen or to oxidized derivatives of NO. The NO release from sodium nitroprusside solution was successfully detected by the probe. An NO probe inserted into the molecular layer of a rat cerebellar slice detected a response corresponding to 8-58 nM of NO concentration following electrical stimulation of the white matter. This response was blocked reversibly by tetrodotoxin (1 microM) and was attenuated in the medium containing hemoglobin (1 or 10 microM). The dependence of the response amplitude on the voltage at the cathode in the probe was the same as that of the NO-induced probe current. These results ensure that the NO probes developed in this study effectively detect the endogenous NO release in brain tissue.