Photochemical and pharmacological evaluation of 7-nitroindolinyl-and 4-methoxy-7-nitroindolinyl-amino acids as novel, fast caged neurotransmitters

J Neurosci Methods. 2001 Nov 15;112(1):29-42. doi: 10.1016/s0165-0270(01)00451-4.


Reagents capable of rapid and efficient release of neuroactive amino acids (L-glutamate, GABA and glycine) upon flash photolysis of thermally stable, inert precursors have been elusive. 7-Nitroindolinyl (NI)-caged and 4-methoxy-7-nitroindolinyl (MNI)-caged compounds that fulfil these criteria are evaluated here. These caged precursors are highly resistant to hydrolysis. Photolysis is fast (half time< or =0.26 ms) and the conversion achieved with a xenon flashlamp is about 15% for the NI-caged L-glutamate and about 35% for the MNI-caged L-glutamate. A procedure is described for calibration of photolysis in a microscope-based experimental apparatus. NI-caged L-glutamate itself showed no agonist or antagonist effects on AMPA and NMDA receptors in cultured neurones, and had no effect on climbing fibre activation of Purkinje neurones. A control compound with identical photochemistry that generated an inert phosphate upon photolysis was used to confirm that the intermediates and by-products of photolysis have no deleterious effects. MNI-caged L-glutamate is as stable and fast as NI-caged L-glutamate and similarly inert at glutamate receptors, but about 2.5 times more efficient. However, NI-caged GABA is an antagonist at GABA(A) receptors and NI-glycine an antagonist at glycine receptors. The results show the utility and limitations of these fast and stable caged neurotransmitters in the investigation of synaptic processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured / drug effects
  • Cells, Cultured / metabolism
  • Excitatory Amino Acid Antagonists / pharmacology
  • Fluorescent Dyes / chemistry
  • Glutamates / pharmacology*
  • Glutamic Acid / analogs & derivatives*
  • Glutamic Acid / metabolism
  • Glycine / analogs & derivatives
  • Glycine / metabolism
  • Indoles / pharmacology*
  • Microscopy, Fluorescence / methods
  • Neurochemistry / methods*
  • Neurons / drug effects
  • Neurons / metabolism
  • Neurotransmitter Agents / metabolism*
  • Nitro Compounds* / chemistry
  • Nitroimidazoles
  • Photochemistry / methods*
  • Photolysis / drug effects*
  • Rats
  • Receptors, Glutamate / drug effects
  • Receptors, Glutamate / metabolism
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • gamma-Aminobutyric Acid / analogs & derivatives
  • gamma-Aminobutyric Acid / metabolism


  • 4-methoxy-7-nitroindolinyl-glutamate
  • Excitatory Amino Acid Antagonists
  • Fluorescent Dyes
  • Glutamates
  • Indoles
  • Neurotransmitter Agents
  • Nitro Compounds
  • Nitroimidazoles
  • Receptors, Glutamate
  • Glutamic Acid
  • gamma-Aminobutyric Acid
  • Glycine