Multiple distinct subtypes of GABAergic neurons in mouse visual cortex identified by triple immunostaining

Abstract

The majority of cortical interneurons use GABA (gamma amino butyric acid) as inhibitory neurotransmitter. GABAergic neurons are morphologically, connectionally, electrically and chemically heterogeneous. In rat cerebral cortex three distinct groups of GABAergic interneurons have been identified by the expression of parvalbumin (PV), calretinin (CR) and somatostatin (SOM). Recent studies in mouse cerebral cortex have revealed a different organization in which the CR and SOM populations are partially overlapping. Because CR and SOM neurons derive from different progenitors located in different embryonic structures, the coexpression of CR + SOM suggests that the chemical differentiation of interneurons is regulated postmitotically. Here, we have taken an important first step towards understanding this process by triple immunostaining mouse visual cortex with a panel of antibodies, which has been used extensively for classifying developing interneurons. We have found at least 13 distinct groups of GABAergic neurons which include PV, CR, SOM, CCK (cholecystokinin), CR + SOM, CR + NPY (neuropeptide Y), CR + VIP (vasointestinal polypeptide), SOM + NPY, SOM + VIP, VIP + ChAT (choline acetyltransferase), CCK + NPY, CR + SOM + NPY and CR + SOM + VIP expressing cells. Triple immunostaining with PV, CR and SOM antibodies during postnatal development further showed that PV is never colocalized with CR and SOM. Importantly, expression of SOM and CR + SOM developed after the percentage of CR cells that do not express SOM has reached the mature level, suggesting that the chemical differentiation of SOM and CR + SOM neurons is a postnatal event, which may be controlled by transcriptional regulation.

MicroRNA-134 activity in somatostatin interneurons regulates H-Ras localization by repressing the palmitoylation enzyme, DHHC9

“…calretinin-positive neurons have been identified as the main interneuronal population postnatally (P0-P14) in rat neocortex, whereas other major interneuronal subtypes such as parvalbumin (PV)-and vasointestinal peptide-positive neurons emerge later (19). The sensor assays in cortical culture showed that similar to SST + neurons, calretinin neurons expressed miR-134 upon bicuculline treatment, and miR-134 activity was absent in untreated cells (Fig.…”

Visual thalamocortical circuits in parvalbumin-deficient mice

“…The visual cortex sends glutamatergic excitatory projections back to dLGN with collaterals to RTN (Alexander et al, 2006;Petrof et al, 2012;Jurgens et al, 2012). A comprehensive, morphological study of the adult mouse visual cortex shows that PV-ir cells account for approximately 40% of GABAergic cortical interneurons (Gonchar et al, 2008). The two main types of cortical PV-ir interneurons are axon initial segmenttargeting chandelier cells and soma-targeting large basket cells (del Río et al, 1994).…”

Inhibitory interneurons in a cortical column form hot zones of inhibition in layers 2 and 5A

“…4). This number represents an upper estimate, because we labeled for one marker at a time and coexpression of a second marker is likely to occur (55). Coverage was extremely low in L1, L2, lower L6A, and L6B.…”

“…Several molecular markers have been used to label putatively distinct subgroups of INs (25,26,55,56). Our data suggest that the coverage of the overall IN population by PV, SOM, and CR is, at most, ∼75% (Fig.…”