Synthesis and biological evaluation of bis-CNB-GABA, a photoactivatable neurotransmitter with low receptor interference and chemical two-photon uncaging properties

J Am Chem Soc. 2014 Feb 5;136(5):1976-81. doi: 10.1021/ja411082f. Epub 2014 Jan 27.

Abstract

Photoactivatable "caged" neurotransmitters allow optical control of neural tissue with high spatial and temporal precision. However, the development of caged versions of the chief vertebrate inhibitory neurotransmitter, γ-amino butyric acid (GABA), has been limited by the propensity of caged GABAs to interact with GABA receptors. We describe herein the synthesis and application of a practically useful doubly caged GABA analog, termed bis-α-carboxy-2-nitrobenzyl-GABA (bis-CNB-GABA). Uncaging of bis-CNB-GABA evokes inward GABAergic currents in cerebellar molecular layer interneurons with rise times of 2 ms, comparable to flash duration. Response amplitudes depend on the square of flash intensity, as expected for a chemical two-photon uncaging effect. Importantly, prior to uncaging, bis-CNB-GABA is inactive at the GABAA receptor, evoking no changes in holding current in voltage-clamped neurons and showing an IC50 of at least 2.5 mM as measured using spontaneous GABAergic synaptic currents. Bis-CNB-GABA is stable in solution, with an estimated half-life of 98 days in the light. We expect that bis-CNB-GABA will prove to be an effective tool for high-resolution chemical control of brain circuits.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cerebellum / drug effects
  • Cerebellum / metabolism
  • Drug Stability
  • Evoked Potentials / drug effects
  • Interneurons / drug effects
  • Interneurons / metabolism
  • Molecular Structure
  • Neurotransmitter Agents / chemical synthesis*
  • Neurotransmitter Agents / chemistry
  • Neurotransmitter Agents / pharmacology
  • Patch-Clamp Techniques
  • Phenylacetates / chemical synthesis*
  • Phenylacetates / chemistry
  • Phenylacetates / pharmacology
  • Photochemical Processes
  • Photons*
  • Receptors, GABA / metabolism*
  • Synaptic Transmission / drug effects
  • gamma-Aminobutyric Acid / analogs & derivatives*
  • gamma-Aminobutyric Acid / chemical synthesis
  • gamma-Aminobutyric Acid / chemistry
  • gamma-Aminobutyric Acid / pharmacology

Substances

  • Neurotransmitter Agents
  • Phenylacetates
  • Receptors, GABA
  • alpha-carboxy-2-nitrobenzyl gamma-aminobutyrate
  • gamma-Aminobutyric Acid