In vivo voltammetric recording with nafion-coated carbon paste electrodes: Additional evidence that ascorbic acid release is monitored

The response of nafion-coated carbon paste electrodes was studied in vitro and in vivo with linear sweep semidifferential voltammetry. In vitro nafion-coated electrodes were insensitive to ascorbic acid (AA) but were equally sensitive to dopamine (DA) as were the uncoated electrodes. In vivo (anterior caudate) nafion-coated electrodes recorded small, poorly defined peaks. However, nafion-coated electrodes were equally responsive to microinfusion of DA as observed with the uncoated electrodes. Nafion-coated electrodes were insensitive to micro-infusion of AA while uncoated electrodes showed a large response to AA. These data suggest that endogenous DA levels are below the sensitivity of carbon paste electrodes in caudate and that the endogenous peaks recorded with uncoated carbon paste electrodes reflect AA.