Trends in Neurosciences

Trends in Neurosciences

Volume 27, Issue 2, February 2004, Pages 90-97
Journal home page for Trends in Neurosciences

Interneuron Diversity series: Molecular and genetic tools to study GABAergic interneuron diversity and function

https://doi.org/10.1016/j.tins.2003.12.008Get rights and content

Abstract

Structural and functional diversity of GABAergic interneurons has become increasingly central in our understanding of the elemental steps of information processing in the brain. The use of different molecular, electrophysiological and anatomical techniques has provided a wealth of new information regarding GABAergic interneurons over the past decade but it has also led to confusion regarding the number of subtypes of GABAergic interneurons. Combinatorial approaches that also consider multiple parameters seem now to offer renewed hope for finally clarifying the structural diversity of GABAergic interneurons. New molecular techniques have become a powerful tool for exposing the functional diversity of GABAergic neurons at the cellular, microcircuit and systems levels. This article reviews literature regarding molecular tools that have been used, or that appear promising for future attempts, to classify GABAergic interneurons. Some important limitations will also be indicated.

Section snippets

Single-cell RT-PCR

Detecting specific mRNA transcripts in a single neuron is a major technical challenge, owing to the very small amounts of mRNA involved. A powerful technique that has been used to study ligand- and voltage-gated channels in GABAergic interneurons is single-cell RT-PCR. The most straightforward RT-PCR strategy is to use the cytoplasm of a cell to test for expression for a single gene 2, 3, 4. A second approach is to split the cytoplasm into as many reactions as genes to be tested before

Correlating molecular and functional studies in GABAergic interneurons

It should be emphasized that when the RT-PCR approach is used alone, the information obtained is descriptive at best, and in fact a carefully carried out in situ hybridization study is equally or even more informative. However, combining RT-PCR and electrophysiological studies in identified neurons yields information that is a prerequisite for subsequent studies aimed at manipulation of key genes and gaining a better understanding of network phenomena.

Some examples will help illustrate how

Transgenic techniques – altering gene expression in GABAergic interneurons

All studies that have demonstrated either the presence or the absence of certain proteins in GABAergic interneurons invariably lead to the question of why GABAergic interneurons require the presence of a particular protein or, conversely, to that of whether the absence is functionally important. A major advance in the pursuit of such questions has been the use of transgenic techniques.

The finding that AMPA receptor properties in GABAergic interneurons are attributable in large measure to low

In vivo labelling of GABAergic interneurons and circuits

A powerful molecular tool for studying GABAergic interneurons functionally is the use of modified bacterial artificial chromosomes (BACs) to generate transgenic mice expressing the in vivo marker GFP. The relatively easy modification of BACs by homologous recombination in Escherichia coli and the subsequent use to generate transgenic animals were first described by Heintz and colleagues [34]. BACs have the advantage of containing long pieces of genomic DNA, increasing the likelihood of correct

Alteration and silencing of GABAergic interneuron activity

An interesting approach for modifying GABAergic interneuron activity is being pursued by Wisden and colleagues [39]. If successful, this will be a very powerful tool to study the function of different GABAergic interneurons at the system level. The method is a combinatorial multistep approach between genetic and pharmacological manipulation of GABAergic interneurons and is based on the finding that modulation of GABAA receptors by benzodiazepines depends on the presence of a single amino acid

Acknowledgements

We would like to thank Antonio Caputi for his critical input and help in the generation of this review.

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