Figure 4

Absence of functional native plasma membrane HMIT with electrophysiological analysis. A Summary data showing that myo-inositol (5 mM) did not evoke any currents at either pH 5.7 or 7.4 in rat cultured cortical neurones. Inset, representative traces of typical recordings. The downward deflections are spontaneously-occurring synaptic currents because TTX was not included as the effects on HMIT-mediated responses were unknown (n numbers in parentheses). B Summary data showing that micro-pressure application of myo-inositol (10 mM) did not induce any current responses in interneurones in different regions of rat hippocampal slices. Inset, representative traces of typical recordings from a CA3 stratum radiatum and a CA3 stratum lacunosum-moleculare interneurone. C Summary data showing that inositol-evoked currents were not observed following a variety of stimulation protocols. (Depol.: three 30 s steps of depolarising current injection in current-clamp mode to induce action potential firing, glutamate, PMA, DiC8, pH 7.0: pressure application of myo-inositol dissolved in pH 7.0 extracellular solution; high K⁺, 30°C: pre-incubation of slices at 30°C for >2 h before recording). Inset, representative traces of a typical recording of a CA3 stratum lacunosum-moleculare interneurone before (control) and after three depolarising steps. The stimulation paradigm did not promote responses to myo-inositol application.