Cation effects on taurine release from brain slices: Comparison to GABA

Abstract

The effects of cations on the spontaneous and potassium-stimulated taurine release from mouse cerebral cortex slices were assessed with an emphasis on the as yet unestablished calcium dependence of the stimulated release. Spontaneous and stimulated GABA release was analyzed for comparison. A depolarizing concentration (50 mM) of potassium ions caused an approximately 3.5-fold increase in taurine release and the omission of sodium a 6-fold enhancement. GABA release was increased by the same stimuli about 20- and 34-fold, respectively. Omission of calcium ions greatly enhanced basal taurine and GABA release when the medium was supplemented with the calcium chelator ethylenediaminetetraacetate. The potassium stimulation was then abolished, however, with taurine even more readily than with GABA. Magnesium and calcium ions had antagonistic effects on the stimulated release, more clearly with taurine than with GABA. Verapamil abolished the potassium stimulation of both taurine and GABA release, the latter being more sensitive. Although the stimulated taurine release was less in magnitude and had a slower time course than the GABA release, the results are not at variance with the possible neurotransmitter role of taurine.

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

“…We have earlier thoroughly characterized the properties of stimulated release of taurine from slices obtained from different brain regions (Korpi and Oja, 1983;Oja and Kontro, 1987;Oja, 1987a, 1988;. In these earlier experiments of ours the release of taurine from brain slices responded to depolarizing stimuli in a manner not always consonant with the results obtained in the above-cited studies on cultured cells, for instance with regard to the dependency of release on extracellular sodium and calcium ions.…”

“…In order to obtain numerical values amenable to quantitative comparisons and statistical estimations, we calculated fractional efflux rate constants to characterize the average magnitudes of taurine release under different experimental conditions as detailed in Oja and Kontro (1987). The constants for the time intervals of 20 to 30 min (k,) and 34 to 50 min (k2) were computed as negative slopes for the regression lines of the logarithm of radioactivity remaining in the slices vs. superfusion time.…”

Roles of taurine-mediated tonic GABAA receptor activation in the radial migration of neurons in the fetal mouse cerebral cortex

“…These transporters belong to a family of Na + and Cl - -dependent neurotransmitter transporters that mediate the uptake of taurine into cells under resting conditions (Molchanova et al, 2004; Tappaz, 2004). Because taurine uptake is driven by the membrane gradient of Na + and Cl - , taurine transporter activity can be reversed by stimuli that alter this gradient (Oja et al, 1985; Oja and Kontro, 1987; Takuma et al, 1996). In the present study, the ambient taurine level in fetal cortical slices was increased via the application of GES.…”

L‐glutamate‐stimulated taurine release from rat cerebral cultured astrocytes

“…As shown in cultured neurons and brain slices (Oja and Kontro, 1987;Schousboe and Pasantes-Morales, 1989), L-glutamate gradually increased astrocytic taurine release along with the incubation time (Fig. 1).…”