Taurine release and swelling of cerebral cortex slices from adult and developing mice in media of different ionic compositions

Abstract

The release of preloaded radiolabeled taurine was studied in superfused cerebral cortex slices obtained from adult and 3-day-old mice in media of varying ionic composition. Our aim was to establish whether the release of taurine from slices evokable by high concentrations of K+ could be attributed solely to cell volume changes or whether it results directly from depolarization of cell membranes. In both age groups hypoosmotic media enhanced the release of taurine. The enhancement was greater in 3-day-old than in adult mice. The K(+)-evoked release of taurine was likewise greater in slices from 3-day-old mice than in slices from adult mice. The K+ stimulation was totally preserved in adult mice and partially preserved in 3-day-old mice when the slices were superfused with Cl(-)-free media, with media in which the K+ x Cl- ionic product was kept constant and with hyperosmotic high-K+ media. The results were practically the same when the permeant anion acetate and the impermeant anion gluconate were used to replace the Cl- deficit. The unstimulated release of preloaded taurine was greatly enhanced in Cl(-)-free media in both age groups. There obtained no statistically significant correlation between the intracellular swelling of slices and the magnitude of taurine release under the present different experimental conditions in either age group. The results show that the K(+)-evoked release of taurine from superfused cerebral cortex slices cannot be solely attributed to depolarization-induced cell swelling. At least a part of the release results directly from membrane depolarization which besides exocytosis apparently also enhances the carrier-mediated release of taurine and inhibits the reuptake of taurine liberated from intracellular compartments.

Changes in the amygdala amino acid microdialysate after conditioning with a cue associated with ethanol

“…An osmoregulatory role for taurine has been suggested both in vitro from observations of stimulated taurine efflux after conditions that lead to swelling of brain cells Oja and Saransaari 1994;Pasantes-Morales et al 1994) and in vivo from increases in taurine microdialysate content after the administration of agents which induce osmolarity changes within the cells such as water intoxication (Wade et al 1988), glutamate analogues (Menendez et al 1989(Menendez et al , 1990 or ethanol (Dahchour et al 1996). Membrane depolarization also induces taurine release from brain cells (Oja and Saransaari 1992), probably secondarily to changes in ionic conductance which accompany depolarization (Huxtable 1989).…”

Taurine in rat posterior pituitary: Localization in astrocytes and selective release by hypoosmotic stimulation

“…Taurine released by brain slices taken from immature animals is much greater than that from mature ones (Oja and Saransaari, 1995). Taurine is indeed released as a consequence of cell volume adjustment from cerebral cortical slices, but this release could arise partially from membrane depolarization Oja and Saransaari, 1992). Microdialysis of brain sites with hypoosmotic solutions resulted in remarkably increased extracellular taurine levels (Solís et al, 1988;Wade et al, 1988;Horn et al, 1995).…”

Histotypic mouse parietal cortex cultures: Excitation/inhibition ratio and ultrastructural analysis

“…Several functions of Tau have been reported in the CNS, such as: (a) prevents cellular death by excitotoxicity through its neuroprotective effects and its influence on Ca 2+ homeostasis (El Idrissi and Trenkner, 1999); (b) acts as the main endogenous agonist of Gly receptors (Flint et al, 1998); (c) activates GABA receptors in vitro (Del Olmo et al, 2000); (d) is one of the most important organic compounds osmotically active in mammalian CNS (Franco et al, 2000;Oja and Saransaari, 1992). Thus, the high degree of neurochemical and morphological development of P5 cultures could be attributed to the trophic role of Tau on neuronal development.…”