Anatomical, Physiological, Molecular and Circuit Properties of Nest Basket Cells in the Developing Somatosensory Cortex

Abstract

Anatomical, electrophysiological and molecular diversity of basket cell-like interneurons in layers II-IV of rat somatosensory cortex were studied using patch-clamp electrodes filled with biocytin. This multiparametric study shows that neocortical basket cells (BCs) are composed of three distinct subclasses: classical large (LBC) and small (SBC) basket cells and a third subclass, the nest basket cell (NBC). Anatomically, NBCs were distinct from LBCs and SBCs in that they formed simpler dendritic arbors and an axonal plexus of inter-mediate density, composed of a few long, smooth axonal branches. Electrophysiologically, NBCs exhibited diverse discharge responses to depolarizing current injections including accommodation, non-accommodation and stuttering. Single-cell multiplex RT-PCR revealed distinct mRNA expression patterns for the calcium binding proteins parvalbumin (PV), calbindin (CB) and calretinin (CR), and the neuropeptides somatostatin (SOM), vasoactive intestinal peptide (VIP), cholecystokinin (CCK) and neuropeptide Y (NPY) for each BC-subclass. SBCs lacked NPY expression but invariably expressed VIP, whereas neither VIP, CR nor SOM expression was detected in LBCs, and VIP and CR expression was absent in NBCs. Electro-physiologically distinct types of NBCs formed GABAergic synapses with specific dynamics onto pyramidal cells (PCs) and received either strongly facilitating or depressing synaptic inputs from PCs. Finally, NBCs were found to be the most common basket cell in layers II/III, while LBCs were the most common in layer IV. These data provide multiparametric distinguishing features of three major subclasses of basket cells and indicate that NBCs are powerful interneurons that provide most of the (peri-)somatic inhibition in the supragranular layers.

What we can do and what we cannot do with fMRI

“…For example, the firing of pyramidal cells in hippocampus is 1.4 Hz, whereas that of interneurons in the strata pyramidale and oriens is 15 Hz and 10 Hz, respectively. Similarly, cortical inhibitory interneurons may discharge 2-3 times faster than pyramidal cells 47 . In principle, inhibition may increase or decrease energy consumption depending on the contribution of the aforementioned factors (for a recent comprehensive review on inhibitory neurons and brain metabolism, see ref.…”

Paravalbumin-Containing Interneuron Connectivity and Critical Period Modulation

“…A previous study in layer 4 of adult cat visual cortex found that up to 79% of basket cell inhibitory connections could be attributed to other basket cells . This finding was estimated based on the bouton size of anatomically identified interneuron synapses, likely including at least a large population of non-PV adapting nest and small basket cells within layer 4 (Dantzker and Callaway, 2000;Wang et al, 2002). Hence, differences in the interneuron populations, criteria for PV interneuron identification and the age and species of animals examined explain the discrepancies with our results.…”

“…Fast-spiking PV cells of layer 4 are mostly large, nest, or clutch/small basket cells with axons and dendrites that ramify within their lamina of origin (Kisvarday et al, 1985;Wang et al, 2002). A noted exception are large basket cells whose axonal arbors can spread to lower layer 2/3 and layer 5/6 .…”

“…A noted exception are large basket cells whose axonal arbors can spread to lower layer 2/3 and layer 5/6 . Other inhibitory interneurons within layer 4 include non-PV nest and small basket cells and double bouquet cells, possessing dendritic trees that terminate within layer 4 Wang et al, 2002). A majority of reciprocal inhibitory interactions in layer 4 are thought to occur between basket cells, while pyramidal and stellate cells are the major excitatory targets of layer 4 inhibition Binzegger et al, 2004;Tamas et al, 1998).…”

“…A vast majority of PV interneurons in layer 2/3 have basket-or chandelier-like morphology, preferentially contacting proximal dendrites, spines, somata and axon initial segments of stellate and pyramidal cells (Akil and Lewis, 1992;DeFelipe and Fairen, 1982;Wang et al, 2002;Williams et al, 1992). To quantify developmental changes in the proportion of GABAergic versus excitatory input to EGFP-PV cells we assessed the number of asymmetric and symmetric synapses made with EGFP-PV neurites and somas within layer 2/3.…”