Quantitative Chemical Composition of Cortical GABAergic Neurons Revealed in Transgenic Venus-Expressing Rats

Abstract

Although neocortical GABAergic (gamma-aminobutyric acidergic) interneurons have been the focus of intense study, especially in the rat, a consensus view of the functional diversity and organization of inhibitory cortical neurons has not yet been achieved. To better analyze GABAergic neurons in the rat, we used a bacterial artificial chromosome (BAC) construct and established 2 lines of transgenic rats that coexpress Venus, a yellow fluorescent protein, with the vesicular GABA transporter. The brain GABA content from both transgenic lines was similar to the level found in wild-type rats. In the frontal cortex, Venus was expressed in >95% of GABAergic neurons, most of which also expressed at least one of 6 biochemical markers, including alpha-actitin-2, which preferentially labeled late-spiking neurogliaform cells. Taking advantage of the fact that Venus expression allows for targeted recording from all classes of nonpyramidal cells, irrespective of their somatic morphologies, we demonstrated that fast-spiking neurons, which were heterogeneous in somatic size as well as vertical dendritic projection, had relatively uniform horizontal dimensions, suggesting a cell type-specific columnar input territory. Our data demonstrate the benefits of VGAT-Venus rats for investigating GABAergic circuits, as well as the feasibility of using BAC technology in rats to label subsets of specific, genetically defined neurons.

Serotonergic Modulation of the Prefrontal Cortex: From Neurons to Brain Waves

“…Akin to previous studies, we stimulated electrically the dorsal raphe nucleus and recorded the responses on parvalbumin-expressing fast-spiking interneurons of the prefrontal cortex. Parvalbumin is a calcium binding protein selectively expressed by this type of interneuron (Kawaguchi & Kubota, 1997;Uematsu et al, 2008). We observed 5-HT1A-mediated decreases and 5-HT2A-mediated increases of activity in 61% and 10% of the recorded cells, respectively (Figure 2).…”

“…Layers 2 and 3 are full of somas of small pyramidal neurons and distinct types of interneurons, whereas layers 5 and 6 are packed with large pyramidal neurons -output neurons whose axons project to subcortical structures-and a myriad of different interneurons. Several classifications of GABAergic interneurons have been made based on their morphology, chemical neuroanatomy and electrophysiological properties (Gupta et al, 2000;Kawaguchi & Kubota, 1997, 1998Markram et al, 2004;Uematsu et al, 2008). Over the last 20 years, many efforts have been made to understand the expression pattern of serotonergic receptors in the heterogeneous neuron types present in the prefrontal cortex.…”

Whole-cell Patch-clamp Recordings from Morphologically- and Neurochemically-identified Hippocampal Interneurons

“…The transgenic rat line expressing Venus / YFP under the vGAT promoter 13 To assess GABA B R-mediated postsynaptic currents in FS-INs, pharmacologically isolated synaptic responses were elicited by extracellular stimulation of inhibitory fibers at the str. radiatum/lacunosum-moleculare border.…”

“…The advent of transgenic mouse lines, expressing the fluorescent proteins in specific interneuron populations offers an elegant solution which makes pre-selection and recording of these neurons much more efficient 2 . Now many transgenic lines, mostly mice, but increasingly also rats 13 are available, facilitating the investigation of interneurons. When using transgenic lines, however, it is essential to establish the extent and the specificity of the reporter expression.…”

“…However, it should be highlighted that many researchers have made use of standard recording ACSF for slice preparation, to great effect 10,11,15 . Morphological integrity depends heavily on the angle at which slices are cut 13 ; which varies by region and cell type. However, many interneurons can be reliably recorded from transverse, coronal or sagittal slices.…”