Monitoring the Stimulated Release of Dopamine with In Vivo Voltammetry. I: Characterization of the Response Observed in the Caudate Nucleus of the Rat

Abstract

Microvoltammetric electrodes were employed in the brain of an anesthetized rat to monitor chemical substances in extracellular fluid following electrical stimulation of the medial forebrain bundle. An increase in concentration of an easily oxidized substance is observed in the caudate nucleus and in the nucleus accumbens. A large amount of evidence suggests that the substance that is observed following stimulation is dopamine. (1) The location of the stimulating electrode must be in known dopaminergic tracts to induce release. (2) Release is most easily observed in brain regions that contain significant numbers of dopamine-containing neurons. (3) Two voltammetric electrodes with very different electrochemical responses provide voltammograms of the released species that are unique for catechols in one case and catecholamines in another case. (4) The amount of 3,4-dihydroxyphenylacetic acid found in striatal tissue by postmortem analysis correlates with the calculated amount of dopamine released. (5) Inhibition of tyrosine hydroxylase, and thus dopamine synthesis, decreases the observed release while inhibition of monoamine oxidase, and thus formation of dopamine metabolites, does not. (6) The dependence of release on stimulation parameters agrees with results obtained with perfusion techniques. Thus, a new method has been developed to characterize endogenous dopamine release in the rat brain and can be used on a time scale of seconds.

Cholinergic Neuronal Modulation Alters Dopamine D2Receptor Availability In Vivo by Regulating Receptor Affinity Induced by Facilitated Synaptic Dopamine Turnover: Positron Emission Tomography Studies with Microdialysis in the Conscious Monkey Brain

“…However, microdialysis assay indicated no significant increase in dopamine concentration in the striatal ECF in the present study. One possible explanation for this discrepancy is that the change in dopamine concentration in ECF measured by microdialysis does not reflect the "true" dopamine release into the synaptic cleft as suggested previously using voltammetry (Kuhr et al, 1984;Kuhr and Wightman, 1986;May, 1988;Grace, 1993). This is unlikely however, because our previous study demonstrated that the same microdialysis assay could detect the enhancement of dopamine synthesis in the neurons (Tsukada et al, 1994a,b), the facilitation of dopamine release by methamphetamine (Tsukada et al, 1999a), and also the increase in the synaptic dopamine level induced by the inhibition of DAT by cocaine and GBR12909 (Tsukada et al, 1999a,b).…”

In vivo comparison of the regulation of releasable dopamine in the caudate nucleus and the nucleus accumbens of the rat brain

“…Stimulated dopamine release The surgical procedure, stimulation parameters, and electrodes and apparatus have been described in detail in a previous publication (Kuhr et al, 1984). Male Sprague-Dawley rats were anesthetized with chloral hydrate and placed in a stereotaxic frame.…”

“…We have previously shown that stimulation of this neuronal tract causes a release of dopamine that can be monitored with a carbon fiber voltammetric electrode implanted at the caudate nucleus Ewing et al, 1983;Kuhr et al, 1984). Dopamine has been identified as the compound detected in the caudate nucleus by voltammetric, anatomical, physiological, pharmacological, and postmortem data.…”

The hypothalamo‐hypophyseal rat explant in vitro: endocrinological studies of the pars intermedia dopaminergic neural input.

“…This may explain why some groups, using lower stimulation frequencies, reported that higher optimum frequencies were needed to reach maximum activation of dopamine neurones when applying shorter stimulation periods. These parameters ranged from 15 s at 100 Hz for dopamine release from the rat median eminence (Sarkar, Gottschall, Meites, Horn, Dow, Fink & Cuello, 1983) to 10 s at 60 Hz for dopamine release from the rat caudate nucleus (Kuhr, Ewing, Caudill & Wightman, 1984), 2 min at 30 Hz for dopamine release from the cat caudate (Voigtlander & Moore, 1971) for 20 min at 15 Hz for increased dopamine synthesis in the rat neostriatum (Murrin & Roth, 1975). Recently, significant levels of dopamine release from the isolated rat n.i.l.…”