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Measurement of Serotonin Turnover Rate in Rat Dorsal Raphe Nucleus by In Vivo Electrochemistry
Author(s) -
Echizen Hirotoshi,
Freed Curt R.
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb02815.x
Subject(s) - dorsal raphe nucleus , pargyline , chemistry , in vivo , serotonin , monoamine oxidase , metabolite , monoamine neurotransmitter , endocrinology , medicine , serotonergic , biochemistry , biology , receptor , microbiology and biotechnology , enzyme
5‐Hydroxytryptamine (5‐HT; serotonin) turnover rate in dorsal raphe nucleus of the urethane‐anes‐thetized rat was estimated by using the in vivo electrochemical detector to measure the decay of extraneuronal 5‐hydroxyindole acetic acid (5‐HIAA) after monoamine oxidase inhibition. Carbon paste electrodes were scanned by semiderivative voltammetry and revealed two peaks: one at +0.15 V and the other at +0.25 V. The higher potential peak is composed primarily of the 5‐HT metabolite 5‐HIAA. After administration of pargyline, 75 mg/ kg i.p., this peak declined exponentially. Regression analysis of these data by an exponential decay model yielded the fractional rate constant 0.82 ± 0.06 h −1 (mean ± SEM). This rate constant of 5‐HIAA disappearance measured by in vivo electrochemistry is identical to the rate constant found by others measuring 5‐HIAA disappearance by direct tissue assay methods. In animals not treated with pargyline, tissue 5‐HIAA concentrations in the dorsal raphe nucleus were measured by HPLC with electrochemical detection. The average 5‐HT turnover rate calculated as the product of the fractional rate constant and steady‐state tissue 5‐HIAA concentration was 12.6 nmol/g/h. These results demonstrate that electrochemical detection of extraneuronal 5‐HIAA combined with monoamine oxidase inhibition can be used to measure neurotransmitter turnover in vivo in a discrete brain region.