Two Functionally Distinct Networks of Gap Junction-Coupled Inhibitory Neurons in the Thalamic Reticular Nucleus

Abstract

Gap junctions (GJs) electrically couple GABAergic neurons of the forebrain. The spatial organization of neuron clusters coupled by GJs is an important determinant of network function, yet it is poorly described for nearly all mammalian brain regions. Here we used a novel dye-coupling technique to show that GABAergic neurons in the thalamic reticular nucleus (TRN) of mice and rats form two types of GJ-coupled clusters with distinctive patterns and axonal projections. Most clusters are elongated narrowly along functional modules within the plane of the TRN, with axons that selectively inhibit local groups of relay neurons. However, some coupled clusters have neurons arrayed across the thickness of the TRN and target their axons to both first-and higher-order relay nuclei. Dye coupling was reduced, but not abolished, among cells of connexin36 knock-out mice. Our results suggest that GJs form two distinct types of inhibitory networks that correlate activity either within or across functional modules of the thalamus.

Electrical synapses connect a network of gonadotropin releasing hormone neurons in a cichlid fish

“…2 M and N). The measured values for CC are consistent with those reported from other neuronal types connected by gap junctions in vertebrate brains (23)(24)(25)(26)(27).…”

“…Moreover, this report adds to the increasing recognition that gap junctions may play a larger role in vertebrate brains than had been previously recognized (32)(33)(34). Gap junctions have been detected in a variety of mammalian brain structures (23)(24)(25)(26)(27), as well as in fish hindbrain Mauthner cells and anterior telencephalic GnRH3 neurons that do not regulate pituitary function (35,36).…”

GABAergic Neuron-Specific Loss of Ube3a Causes Angelman Syndrome-Like EEG Abnormalities and Enhances Seizure Susceptibility

“…Although this theta abnormality is most prominent in occipital regions, it seems to disappear by adolescence (Laan et al, 1997), perhaps explaining why we did not record significant enhancements in theta power in adult Ube3a STOP/p+ or Ube3a FLOX/p+ ::Gad2-Cre mice despite recording from V1 (Figure 6). Future work in AS models should focus on factors known to affect TRN neuron excitability and synchrony – including relative levels of excitatory and inhibitory synaptic drive, the integrity of gap junctions (Proulx et al, 2006; Lee et al, 2014), the expression of T-type calcium channels (Tsakiridou et al, 1995; Zhang et al, 2009), and cholinergic input (McCormick and Prince, 1986; Sun et al, 2013). However, intracortical GABAergic mechanisms that underlie pathological spike-wave discharges also remain of interest, especially those that engage disinhibitory circuitry (Pi et al, 2013; Hall et al, 2015).…”

An Interneuron Circuit Reproducing Essential Spectral Features of Field Potentials

“…On the other hand, it has been argued that cerebellar cortex and neocortex may generate the same rhythms independently (Niedermeyer, 2004). Given the abundance of electrically coupled inhibitory circuits in the brain (Hestrin & Galarreta, 2005;Lee et al, 2014), it may be worth considering the present mechanisms for the spectral properties of other regions and of neocortex in particular, taking into account the obvious differences in synaptic organization. One of the major differences is the putative lack of recurrent excitation in cerebellar cortex.…”