Figure 3.

Chronic lithium exposure inhibits glutamate-induced ⁴⁵Ca²⁺ influx into cerebellar granule cells. (A) Time course of basal and glutamate-induced ⁴⁵Ca²⁺ influx. Cells were treated with LiCl (3 mM) for 7 days before adding 100 μM glutamate and ⁴⁵CaCl₂ (1 μCi/ml) to the culture medium. At indicated times, the influx was terminated by rapid washing of the culture dishes three times with ice-cold buffer (154 mM choline chloride/2 mM EGTA/10 mM Hepes, pH 7.4) and then solubilized in 0.6 ml of 0.5 M NaOH. An aliquot of 0.5 ml was used for measuring ⁴⁵Ca²⁺ radioactivity and the remainder was used for protein determination. (B) Concentration dependence of inhibition by lithium of the ⁴⁵Ca²⁺ influx. Cells were pretreated chronically (7 days) or acutely (1 h) with various concentrations of LiCl (0.1–5 mM) and then exposed to glutamate (100 μM) in the presence of ⁴⁵Ca²⁺. The ⁴⁵Ca²⁺ influx was determined 10 min after glutamate addition. When used, the concentrations of MK-801, 2-amino-5-phosphonopentanoate (APV), and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were 1 μM, 200 μM, and 20 μM, respectively. Data are the mean ± SEM of ⁴⁵Ca²⁺ uptake measurements from three cultures. ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001, compared with the group treated with glutamate alone (one-way ANOVA with Bonferroni–Dunn test).