Electrical synapses between Gaba-Releasing interneurons

Abstract

Although gap junctions were first demonstrated in the mammalian brain about 30 years ago, the distribution and role of electrical synapses have remained elusive. A series of recent reports has demonstrated that inhibitory interneurons in the cerebral cortex, thalamus, striatum and cerebellum are extensively interconnected by electrical synapses. Investigators have used paired recordings to reveal directly the presence of electrical synapses among identified cell types. These studies indicate that electrical coupling is a fundamental feature of local inhibitory circuits and suggest that electrical synapses define functionally diverse networks of GABA-releasing interneurons. Here, we discuss these results, their possible functional significance and the insights into neuronal circuit organization that have emerged from them.

Mechanisms of physiological and epileptic HFO generation

“…Subsequent investigations suggested that gap junction coupling between interneurons (Galarreta and Hestrin, 2001) helps "sharpen" the tuning of γ oscillations, presumably by helping synchronize interneuronal action potentials as the IPSPs wane (Beierlein et al, 2000;Fukuda and Kosaka, 2000;Tamas et al, 2000;Traub et al, 2001a). Fast spiking interneurons do not seem to sustain subthreshold resonance, so intrinsic properties are unlikely to contribute to these kinds of coherent γ oscillation, which argues for a synaptic mechanism (Zemankovics et al, 2010).…”

Gap junctions promote synchronous activities in a network of inhibitory interneurons

“…Recent experimental findings suggest that neocortical and hippocampal interneurons innervating the perisomatic region of pyramidal cells coordinate neural oscillatory activity (Fisahn and McBain, 2001;Galarreta and Hestrin, 2001a). Moreover, the synchronous firing of a neural population in the gamma frequency band (30-100 Hz) seems to be associated to cognitive functions (Gray et al, 1989;Csicsvari et al, 2003).…”

The Role of Intrinsic Cell Properties in Synchrony of Neurons Interacting via Electrical Synapses

“…Therefore, certain types of neurons (e.g., FS cells Gibson et al 1999;Galarreta and Hestrin 2001 or multipolar bursting Blatow et al 2003 in neocortex) often interact through both electrical and GABAergic synapses. This raises the question of the effect of their combination in neural synchrony.…”

“…This is, for instance, the case in the striatum (Kita et al 1990), the hippocampus (Venence et al 2000), the cerebellum (MannMetzer and Yarom 1999), the reticular thalamic nucleus (Landisman et al 2002), or in the neocortex (Gibson et al 1999;Galarreta and Hestrin 1999;Fukuda and Kosaka 2000). In the neocortex, electrical as well as inhibitory synapses exist between Fast-Spiking (FS) interneurons (Gibson et al 1999;Galarreta and Hestrin 2001) or between Multipolar Bursting neurons (Blatow et al 2003). In contrast, low-threshold-spiking (LTS) interneurons interact mostly via electrical synapses, the inhibitory synapses between them being sparse (Gibson et al 1999;Amitai et al 2002).…”