Expression of Gap Junction Protein Connexin36 in Multiple Subtypes of GABAergic Neurons in Adult Rat Somatosensory Cortex

Abstract

To characterize connexin36 (Cx36)-expressing neurons of the adult rat somatosensory cortex, we examined fluorescence signals for Cx36 messenger RNA (mRNA) in 3 nonoverlapping subpopulations of γ-aminobutyric acid (GABA)ergic interneurons, which showed immunoreactivity for 1) parvalbumin (PV); 2) somatostatin (SOM); and 3) either calretinin (CR), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), or choline acetyltransferase (ChAT). About 80% of PV-, 52% of SOM-, 37% of CR/VIP/CCK/ChAT-immunoreactive cells displayed Cx36 signals across all cortical layers, and inversely 64%, 25%, and 9% of Cx36-expressing neurons were positive for PV, SOM, or CR/VIP/CCK/ChAT, respectively. Notably, although almost all Cx36-expressing neurons in layer (L) 4, L5, and L6 were positive for one of these markers, a substantial proportion of those in L1 (91%) and L2/3 (10%) were negative for the markers tested, suggesting that other types of neurons might express Cx36. We further investigated the colocalization of Cx36 mRNA and α-actinin2 immunoreactivity, as a marker for late-spiking GABAergic neurons, by using mirror-image sections. Surprisingly, more than 77% of α-actinin2-positive cells displayed Cx36 signals in L1-L3, and about 49% and 13% of Cx36-expressing neurons were positive for α-actinin2 in L1 and L2/3, respectively. These findings suggest that all the subtypes of GABAergic interneurons might form gap junctions in the neocortex.

Strategies and Tools for Combinatorial Targeting of GABAergic Neurons in Mouse Cerebral Cortex

“…The intrinsic properties of a substantial proportion of VIP/CCK cells were either bursting or fast-adapting, which were less frequently observed in VIP/CR cells (Figure 3G, Table S3). These morphological and physiological features suggest that VIP/CCK cells likely correspond to a set of VIP− and CCK-expressing small basket cells (Kawaguchi and Kubota, 1998; Kubota, 2014; Ma et al, 2011). It is notable that this population appears to be found in a large scale recording in juvenile rat (Markram et al, 2015) but was undetected by similar studies in the mouse even using the VIP-ires-Cre driver (Jiang et al, 2015; Pronneke et al, 2015).…”

Differential Inputs to the Perisomatic and Distal-Dendritic Compartments of VIP-Positive Neurons in Layer 2/3 of the Mouse Barrel Cortex

“…The following hybridization procedure was performed as previously reported (Hioki et al, 2010, 2013; Ma et al, 2011; Sohn et al, 2014). Briefly, free-floating brain sections were hybridized at 60°C with 1 μg/ml cRNA probes in a hybridization buffer.…”

Divergent localization of angiotensinogen mRNA and protein in proximal tubule segments of normal rat kidney

“…We also performed double staining using FISH and immunofluorescence methods [27–29]. Before the incubation with Streptavidin, Alexa Fluor 488 conjugate in the FISH method, the sections were incubated with rabbit polyclonal anti-SGLT2 antibody (1 : 100; Santa Cruz Bio-technology), goat polyclonal anti-CA IV antibody (1 : 100), or rabbit polyclonal antiecto-ATPase antibody (1 : 100; Santa Cruz Biotechnology) for 1 h at room temperature.…”