DPNI-caged-GABA

IC50: N/A

DPNI-GABA, also known as Nitroindoline-caged GABA, has similar photochemical properties with MNI-glutamate, including the same quantum yield (0.085), highly water soluble, exhibitting fast photorelease that is efficient at near-UV and 405 nm wavelengths.

In vitro: Under the condition of retaining the advantages of nitroindoline cages, DPNI-GABA were modified to minimize the pharmacological interference commonly found with caged GABA reagents. Unlike previous test of the 5-methoxycarbonylmethyl-7-nitroindolinyl-GABA, DPNI-GABA reduced peak GABA-evoked responses with an IC50 of approximately 0.5mM, and blocked GABAA receptors with much lower affinity,. It is most important that the kinetics of receptor activation, comparable to synaptic events, were determined as 10–90% rise-times, and had no effect by DPNI-GABA present at 1 mM concentration, and permitted photolysis of DPNI-GABA to mimic synaptic activation of GABAA receptors. As estimated, the spatial resolution of uncaging DPNI-GABA in dendrites was 2m laterally and 7.5m focally with a laser spot of 1mapplied to cerebellar molecular layer interneurons. Finally, photorelease restricted to the area of the soma inhibited spiking in single Purkinje neurons or molecular layer interneurons for periods regulated by the flash intensity and duration at low DPNI-GABA concentration [1,2].

Under resting conditions, miniature synaptic currents have long been known to represent random transmitter release, but their nature and function in central synapses much remains to be learned about. A new class of miniature currents (‘‘preminis’’) arise by the autocrine activation of axonal receptors following random vesicular release. During the development of the molecular layer, preminis are prominent in gabaergic synapses made by cerebellar interneurons. Premini frequencies, unlike ordinary miniature postsynaptic currents in the same cells, are strongly enhanced by subthreshold depolarization, suggesting that themembrane depolarization they produce belongs to a feedback loop controlling neurotransmitter release. Thus, preminis enhanced neurotransmitter release to guide the formation of the interneuron network at recently formed synaptic contacts [3].

In vivo: So far, no study in vivo has been conducted

Clinical trial: So far, no clinical study has been conducted.

References:
[1].  Wieboldt R, Ramesh D, Carpenter BK, Hess GP. Synthesis and photochemistry of photolabile derivatives of gamma-aminobutyric acid for chemical kinetic investigations of the gamma-aminobutyric acid receptor in the millisecond time region. Biochemistry. 1994 Feb 15;33(6):1526-33.
[2].  Trigo FF, Papageorgiou G, Corrie JE, Ogden D. Laser photolysis of DPNI-GABA, a tool for investigating the properties and distribution of GABA receptors and for silencing neurons in situ. J Neurosci Methods. 2009 Jul 30;181(2):159-69. doi: 10.1016/j.jneumeth.2009.04.022. Epub 2009 May 5.
[3].  Trigo FF, Bouhours B, Rostaing P, Papageorgiou G, Corrie JE, Triller A, Ogden D, Marty A. Presynaptic miniature GABAergic currents in developing interneurons. Neuron. 2010 Apr 29;66(2):235-47.

Presynaptic miniature GABAergic currents in developing interneurons.[Pubmed:20435000]

Neuron. 2010 Apr 29;66(2):235-47.

Miniature synaptic currents have long been known to represent random transmitter release under resting conditions, but much remains to be learned about their nature and function in central synapses. In this work, we describe a new class of miniature currents ("preminis") that arise by the autocrine activation of axonal receptors following random vesicular release. Preminis are prominent in gabaergic synapses made by cerebellar interneurons during the development of the molecular layer. Unlike ordinary miniature postsynaptic currents in the same cells, premini frequencies are strongly enhanced by subthreshold depolarization, suggesting that the membrane depolarization they produce belongs to a feedback loop regulating neurotransmitter release. Thus, preminis could guide the formation of the interneuron network by enhancing neurotransmitter release at recently formed synaptic contacts.

Laser photolysis of DPNI-GABA, a tool for investigating the properties and distribution of GABA receptors and for silencing neurons in situ.[Pubmed:19422852]

J Neurosci Methods. 2009 Jul 30;181(2):159-69.

Laser photolysis to release GABA at precisely defined times and locations permits investigation of the distribution of functional GABA(A) receptors in neuronal compartments, the activation kinetics and pharmacology of GABA(A) receptors in situ, and the role of individual neurons in neural circuits by selective silencing with low GABA concentrations. We describe the experimental evaluation and applications of a new nitroindoline-caged GABA, DPNI-GABA, modified to minimize the pharmacological interference commonly found with caged GABA reagents, but retaining the advantages of nitroindoline cages. Unlike the 5-methoxycarbonylmethyl-7-nitroindolinyl-GABA tested previously, DPNI-GABA inhibited GABA(A) receptors with much lower affinity, reducing peak GABA-evoked responses with an IC(50) of approximately 0.5 mM. Most importantly, the kinetics of receptor activation, determined as 10-90% rise-times, were comparable to synaptic events and were little affected by DPNI-GABA present at 1mM concentration, permitting photolysis of DPNI-GABA to mimic synaptic activation of GABA(A) receptors. With a laser spot of 1 microm applied to cerebellar molecular layer interneurons, the spatial resolution of uncaging DPNI-GABA in dendrites was estimated as 2 microm laterally and 7.5 microm focally. Finally, at low DPNI-GABA concentration, photorelease restricted to the area of the soma suppressed spiking in single Purkinje neurons or molecular layer interneurons for periods controlled by the flash intensity and duration. DPNI-GABA has properties better adapted for fast kinetic studies with laser photolysis at GABA(A) receptors than previously reported caged GABA reagents, and can be used in experiments where spatial resolution is determined by the dimensions of the laser light spot.

Synthesis and photochemistry of photolabile derivatives of gamma-aminobutyric acid for chemical kinetic investigations of the gamma-aminobutyric acid receptor in the millisecond time region.[Pubmed:8312272]

Biochemistry. 1994 Feb 15;33(6):1526-33.

The gamma-aminobutyric acid (GABA) receptor is an abundant neuronal receptor in the mammalian and invertebrate nervous systems and is associated with an inhibitory chloride ion channel. GABA is the endogenous neurotransmitter for the receptor and can trigger both fast activation and a reversible desensitization of the receptor. A series of photolabile amine-linked o-nitrobenzyl derivatives of GABA were synthesized that photolyze rapidly to release free GABA. The photochemical properties of the GABA precursors were determined; the compounds undergo rapid photolysis, initiated with UV irradiation at 308 nm, and release free GABA on a millisecond time scale. The pH of the photolysis medium affects both the quantum yield and the rate of photolysis. For example, the quantum yield observed for N-(alpha-carboxy-2-nitrobenzyl)-gamma-aminobutyric acid increases from 0.06 at pH 5.0 to 0.1 at pH 10.5, and the half-life for the photolytic reaction decreases from 1.0 to 2.5 ms in the same pH range. Photolysis of the compounds induces rapid onset of transmembrane ion currents in mouse cortical neurons. The potential of the new compounds for use in rapid chemical kinetic investigations of the neuronal GABA receptor is demonstrated.