GABAergic and glutamatergic currents in hippocampal slices and neuronal cultures show profound differences: a clue to a potent homeostatic modulation.

Acute hippocampal slices and primary neuronal cultures are often used with a tacit assumption that basic characteristics of the two models closely resemble each other. The use of the cell cultures, however, may raise controversies because of non-physiological conditions resulting from e.g. glial cells deficit, random neuronal sprouting, lack of specificity in the synaptic connections, impaired homeostasis, etc. Importantly, alteration in neuronal environment, especially when occurring over a prolonged period of time, may give rise to a profound homeostatic modulation. In the present study we have compared the properties of GABAergic and glutamatergic (non-NMDA) currents in pyramidal neurons from hippocampal slices and neuronal cell culture. We show that, most strikingly, amplitude ratio of currents elicited by ultrafast applications of saturating GABA and glutamate was nearly one order of magnitude larger in cultured neurons than that in slices. Miniature IPSCs and EPSCs also showed substantial differences between these two models. In particular, mEPSC amplitudes were larger and more frequent in cultured neurons but their time duration was longer in slices. Miniature IPSCs did not show differences in amplitude when comparing slices and cultures but their time duration was faster and occurrence more frequent in slices. In conclusion, we provide evidence that expression pattern of GABA(A) and glutamate receptors as well as synaptic current properties in the neuronal cell culture show profound differences with respect to that in the physiological conditions.