FAST-SCAN CYCLIC VOLTAMMETRY OF 5-HYDROXYTRYPTAMINE

Fast-scan cyclic voltammetry, a demonstrated analytical method for the in vivo detection of dopamine, is extended to the detection of in vitro and in vivo 5-hydroxytryptamine (5-HT) with the use of a specific potential wave form applied at 1000 V/s. The wave form, 0.2 to 1.0 to -0.1 to 0.2 V, is employed to accelerate electrode response times which are significantly slower with other wave forms due to the adsorption of 5-HT. The scan rate of 1000 V/s enables follow-up reactions which lead to the formation of strongly adsorptive products to be outrun, The peak current at a carbon fiber disk microelectrode exposed to 1 mu M 5-HT in now injection experiments is 1 nA, with a half-rise time of less than 200 ms, The peak current of Nafion-coated electrodes exposed to the same concentration of 5-HT is 5 nA,with a half-rise time on the order of 400 ms, The rate of adsorption of 5-HT was determined to be 4.22 +/- 0.33 s(-1). Several compounds present in brain tissue as well as the pharmacological agents used to elicit 5-HT release in the caudate of the rat were evaluated, Those which gave a response could be differentiated from 5-HT on the basis of respective oxidative and reductive peak potentials, Nafion-coated electrodes were used to monitor transient increases in both dopamine and exogenous 5-HT in the caudate of the anesthetized rat in response to electrical stimulation. The rate of cellular uptake of 5-HT was shown to be 3-fold slower than dopamine uptake.