Engineering topics

Schaechter, Judith D.

Publications and source records attributed to Schaechter, Judith D..

4 records

NASA NTRS1990

Serotonin release varies with brain tryptophan levels

This study examines directly the effects on serotonin release of varying brain tryptophan levels within the physiologic range. It also addresses possible interactions between tryptophan availability and the frequency of membrane depolarization in controlling serotonin release. We demonstrate that reducing tryptophan levels in rat hypothalamic slices (by superfusing them with medium supplemented with 100 microM leucine) decreases tissue serotonin levels as well as both the spontaneous and the electrically-evoked serotonin release. Conversely, elevating tissue tryptophan levels (by superfusing slices with medium supplemented with 2 microM tryptophan) increases both the tissue serotonin levels and the serotonin release. Serotonin release was found to be affected independently by the tryptophan availability and the frequency of electrical field-stimulation (1-5 Hz), since increasing both variables produced nearly additive increases in release. These observations demonstrate for the first time that both precursor-dependent elevations and reductions in brain serotonin levels produce proportionate changes in serotonin release, and that the magnitude of the tryptophan effect is unrelated to neuronal firing frequency. The data support the hypothesis that serotonin release is proportionate to intracellular serotonin levels.

Schaechter, Judith D.↗

NASA NTRS1989

Tryptophan availability modulates serotonin release from rat hypothalamic slices

The relationship between the tryptophan availability and serononin release from rat hypothalamus was investigated using a new in vitro technique for estimating rates at which endogenous serotonin is released spontaneously or upon electrical depolarization from hypothalamic slices superfused with a solution containing various amounts of tryptophan. It was found that the spontaneous, as well as electrically induced, release of serotonin from the brain slices exhibited a dose-dependent relationship with the tryptophan concentration of the superfusion medium.

Schaechter, Judith D.↗

NASA NTRS1989

Effect of chronic D-fenfluramine administration on rat hypothalamic serotonin levels and release

The effect of administering to rats (in doses of 1.25, 2.5, 5, or 10 mg/kg/day for 10 days) of an anorectic agent, D-fenfluramine, on the serotonin levels in hypothalamic tissue and on the in vitro release of serotonin by hypothalamic slices was investigated in rats which were sacrificed six days after the end of treatment. It was found that D-fenfuramine had no effect on tissue serotonin in doses from 1.25 to 5 mg/kg. However, given at 10 mg/kg level, serotonin led to a 22 percent decrease. The release of serotonin was found to be not affected by D-fenfluramine.

Schaechter, Judith D.↗

NASA NTRS1988

Effect of chronic d-fenfluramine administration on rat hypothalamic serotonin levels and release

D-fenfluramine, an anorectic agent in rats and man, was administered daily at doses 1.25, 2.5, 5, or 10 mg/kg/day for 10 days, and sacrificed 6 days later. Hypothalamic serotonin (5-HT) levels were unchanged in rats receiving 1.25-5 mg/kg/day of d-fenfluramine but reduced by 22 percent (p less than 0.01) at the highest drug dose (10 mg/kg/day); hypothalamic 5-hydroxyindole acetic acid (5-HIAA) levels were reduced by 15 percent (p less than 0.05) or 28 percent (p less than 0.01) in rats receiving 5 or 10 mg/kg/day of the drug, respectively. Hypothalamic slices prepared from rats which were previously treated with any of the drug doses spontaneously released endogenous 5-HT at rates that did not differ from those of vehicle-treated rats. 5-HT released with electrical field-stimulation was unaffected by prior d-fenfluramine treatment at doses of 1.25-5 mg/kg/day, and was reduced by 20 percent (p less than 0.05) from slices prepared from rats which received 10 mg/kg/day. 5-HIAA efflux was also attenuated by the highest drug dose. These data indicate that chronic administration to rats of customary anorectic doses of d-fenfluramine (i.e. 0.06-1.25 mg/kg) fail to cause long-lasting reductions in brain 5-HT release.

Schaechter, Judith D.↗