THE UPTAKE OF 5-HYDROXYTRYPTAMINE AND HISTAMINE BY PARTICULATE FRACTIONS OF BRAIN

¹ Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut

Nerve ending particles and microsomes isolated from rat brain took up both 5-hydroxytryptamine and histamine in similar fashion, the quantity of amine taken imp increasing as the concentration of amine in the incubation medium was increased. The amine that was taken up by the particles was at a higher concentration than that in the medium, although the majority of the 5-HT taken up could be removed by three washes with sucrose. The quantity of amine taken up by particles incubated at 0°C was one-half to two-thirds that taken up by particles incubated at 37°C.

The uptake of 5-hydroxytrptamine by the particles was diminished by increasing concentrations of hydrogen ions, divalent cations, and monovalent cations in a manner suggesting the uptake of the amines was a nonspecific ion-exchange process. Titration of suspensions of the nerve ending particles revealed a great capacity for binding cations. When the nerve-ending particles were incubated in a medium containing 5-hydroxytryptophan and the supernatant fraction of brain, the 5-hydroxytryptamine that was formed was also taken up.