Differentiation of Dopamine Overflow and Uptake Processes in the Extracellular Fluid of the Rat Caudate Nucleus with Fast-Scan In Vivo Voltammetry
Version of Record online: 5 OCT 2006
Journal of Neurochemistry
Volume 51, Issue 4, pages 1060–1069, October 1988
How to Cite
May, L. J., Kuhr, W. G. and Wightman, R. M. (1988), Differentiation of Dopamine Overflow and Uptake Processes in the Extracellular Fluid of the Rat Caudate Nucleus with Fast-Scan In Vivo Voltammetry. Journal of Neurochemistry, 51: 1060–1069. doi: 10.1111/j.1471-4159.1988.tb03069.x
- Issue online: 5 OCT 2006
- Version of Record online: 5 OCT 2006
- Received January 19, 1988; revised manuscript received March 28, 1988; accepted April 5, 1988.
- In vivo voltammetry;
- Uptake inhibition;
Abstract: Stimulated overflow of dopamine (DA) into the extracellular fluid of the rat caudate nucleus was measured with fast-scan cyclic voltammetry. DA concentrations were sampled in less than 10 ms at 100-ms intervals with a Na-fion-coated, carbon-fiber microelectrode. Overflow of DA was induced by electrical stimulation of the medial fore-brain bundle with 300–μA pulses of various duration and frequency. Stimulated overflow was measured as a function of stimulus duration before and after administration of benztropine, bupropion, and amphetamine. These results were correlated with simulated curves based on a simple uptake/overflow model. The observed overflow was assumed to be a function of [DA]P, the concentration of DA which overflows per stimulus pulse, and the kinetics of cellular uptake of DA. Correlation of experimental with simulated results was obtained at the 95% confidence limit for the duration studies; however, it was not possible to distinguish between the effects of pharmacological agents on uptake and overflow. In contrast, modulation of stimulus frequency did permit such distinction. Simulations of an increase in [DA]P fit results following dihydroxyphenyl-alanine methyl ester at 95% confidence limits, whereas an equivalent change in the apparent Km did not fit. An increase in the apparent value of Km correlated with results obtained at different frequencies following nomifensine and bupropion administration at the 95% confidence limit, whereas an equivalent increase in [DA]P did not fit. The effects of GBR 12909 best correlated with an increase in the DA available for overflow.