Calcium dependence of glutamate receptor-evoked alkaline shifts in hippocampus

Glutamate receptor activation induces an extracellular alkalinization in rodent hippocampus. We studied its Ca2+ dependence and pharmacology in hippocampal slices. Glutamate-evoked alkaline shifts were blocked by 0 Ca2+ saline. Alkalinizations induced by AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and NMDA (N-methyl-D-aspartate) were abolished by 20 microM CNQX (6-cyano-7-nitro-nitroquinoxaline-2,3-dione) and 50 microM APV (DL-2-amino-5-phosphonovalerate), respectively. The AMPA- and NMDA-evoked alkaline shifts were blocked by 0 Ca2+, however, AMPA-induced [K+]o elevation was unaffected. These data suggest that the glutamate receptor-channel does not mediate H+ influx, and support a role for Ca(2+)-H+ exchange.