Glutamate induces Ca2+ influx via both glutamate receptors and voltage-gated Ca2+ channels in third-order neurons. (A) Glutamate-induced [Ca2+]i is completely blocked by ionotropic glutamate receptor antagonists, CNQX (50µM) and AP-7(40µM). (B) Co2+ blocks voltage-gated Ca2+ channels, which reduces 55% of glutamate-induced [Ca2+]i in the neurons (see asterisk); with Co2+ taurine still suppresses glutamate-induced [Ca2+]i. (C) Ruthenium red (1µM), a rynadine receptor inhibitor, reduces 15% of glutamate-induced [Ca2+]i; with ruthenium red, taurine has 35% suppression on glutamate-induced [Ca2+]i in the neurons. (D) Blocking Ca2+ uptake pumps in the internal organelles with thapsigargin (1µM) had a limited effect on taurine regulation of [Ca2+]i.