FADING - NEW CYTOFLUORIMETRIC MEASURE QUANTIFYING SEROTONIN IN PRESENCE OF CATECHOLAMINES AT CELLULAR LEVEL IN BRAIN

  • 1 January 1978
    • journal article
    • research article
    • Vol. 207  (2) , 650-667
Abstract
A new histopharmacological approach to the study of serotonergic neurons is described. A computerized microspectrofluorimeter was used to show that a measure of fluorescence fading reliably detects changes in serotonin even in the presence of catecholamines. This fading measure was validated with model droplets containing serotonin, norepinephrine or mixtures of the 2 and with in vivo studies using pargyline to increase brain serotonin. After various doses of pargyline, a correlation of 0.927 was found between the intraperikaryal fading measure and a standard fluorimetric measure of serotonin in dissected samples of the rat raphe. The feasibility of the cytofluorimetric fading measure for quantifying differential changes in serotonin in intraperikaryal and extraperikaryal regions was tested. Both LSD (75 and 150 .mu.g/kg) and a low dose of the monoamine oxidase inhibitor pargyline (25 mg/kg) increased intraperikaryal serotonin without affecting extraperikaryal fluorescence. The serotonin reuptake inhibitor fluoxetine produced the opposite effect of selectively increasing extraperikaryal serotonin. Another inhibitor of serotonin reuptake, chlorimipramine, which also blocks reuptake of norepinephrine in vivo, markedly increased both intraperikaryal and extraperikaryal serotonin. The utility of cytofluorimetric measures of serotonin within raphe cell bodies from untreated rats is confirmed; changes in the intracellular and extracellular concentrations of serotonin apparently can be differentiated.