ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Application of a novel in vitro experimental system has allowed us to describe the relationship between tryptophan availability and serotonin release from rat hypothalamic slices. Superfusing hypothalamic slices with a physiologic medium containing l-tryptophan (1, 2, 5, or 10 μM) caused dose-dependent elevations in tissue tryptophan levels; the magnitude of the elevations produced by supplementing the medium with 〈5 μM tryptophan was within the physiologic range for rat brain tryptophan levels. Slice serotonin levels rose biphasically as the tryptophan concentration in the medium was increased. Superfusing the slices with medium supplemented with a low tryptophan concentration (1 or 2 μM) caused proportionally greater incremental changes in serotonin levels than the increases caused by further elevating the tryptophan concentration (5 or 10 μM). The spontaneous release of serotonin from the slices exhibited a dose-dependent relationship with the tryptophan concentration of the super-fusion medium. Electrically evoked serotonin release, which was calcium-dependent and tetrodotoxin-sensitive, also increased in proportion to the medium tryptophan concentration. These data suggest that the rate at which serotonin is released from hypothalamic nerve terminals is coupled to brain tryptophan levels. Accelerations in hypothalamic serotonin synthesis, caused by elevating brain tryptophan levels, result in proportionate increases in the rates of serotonin release during rest and with membrane depolarization.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1989.tb09263.x
