In this paper, we present an additional, new cage-GABA compound, called 4-amino-1-(4′-dimethylaminoisopropoxy-5′,7′-dinitro-2′,3′-dihydro-indol-1-yl)-1-oxobutane-γ-aminobutyric
acid (iDMPO-DNI-GABA), and currently, this compound is the only photoreagent, which
can be applied for GABA uncaging without experimental compromises. By a systematic
theoretical design and successful synthesis of several compounds, the best reagent
exhibits a high two-photon efficiency within the 700–760 nm range with excellent pharmacological
behavior, which proved to be suitable for a complex epileptic study. Quantum chemical
design showed that the optimal length of the cationic side chain enhances the two-photon
absorption by 1 order of magnitude due to the cooperating internal hydrogen bonding
to the extra nitro group on the core. This feature increased solubility while suppressing
membrane permeability. The efficiency was demonstrated in a systematic, wide range
of in vitro single-cell neurophysiological experiments by electrophysiological as
well as calcium imaging techniques. Scalable inhibitory ion currents were elicited
by iDMPO-DNI-GABA with appropriate spatial–temporal precision, blocking both spontaneous
and evoked cell activity with excellent efficiency. Additionally, to demonstrate its
applicability in a real neurobiological study, we could smoothly and selectively modulate
neuronal activities during artificial epileptic rhythms first time in a neural network
of GCaMP6f transgenic mouse brain slices.
