[Neuropsychopharmaca influence the intracellular pH value of central neurons]

The intracellular pH (pHi) of neurons is tightly regulated, mainly by membrane-bound transporters acting as acid extruders or acid loaders. Regulation of pHi helps to control neuronal excitability, as increased bioelectric activity moderately lowers pHi and, in the sense of a negative feedback loop, intracellular acidosis mostly reduces neuronal excitability. Moreover, a change of pHi widely influences complex cellular functions. With respect to neuropsychopharmaca, little is known about whether or not they may affect neuronal H ( + )-homeostasis. To this aim, we tested several antipsychotics, antidepressants, anticonvulsants, and lithium for effects on neuronal pHi, using guinea pig hippocampal slice preparations in which CA 3 pyramidal neurons were loaded with the pHi-sensitive dye BCECF-AM. All antipsychotics, most antidepressants and about half of the anticonvulsants tested so far elicited reversible changes of neuronal pHi when applied at therapeutic and supratherapeutic concentrations. Although these results await confirmatory in vivo experiments, we believe that the pHi activity of neuropsychopharmaca needs further attention, especially when therapeutic mechanisms or even harmful side effects are discussed.