, 1996) Thus far, most attention has been focused on short-term

, 1996). Thus far, most attention has been focused on short-term interactions between electrical and chemical synapses on the millisecond timescale, but it has long been speculated

that chemical synapses may also drive long-term regulation of mammalian electrical synapses see more (Connors and Long, 2004). Electrical synapses can undergo long-term modification by spiking activity (Haas et al., 2011), metabotropic neurotransmitters (Landisman and Connors, 2005 and Mills and Massey, 1995), and dopaminergic activation (Kothmann et al., 2009). While experiments in goldfish Mauthner cells have shown that activation of fast glutamatergic synapses can produce long-term potentiation of neighboring electrical synapses (Yang et al., 1990, Pereda and Faber, 1996 and Smith and Pereda, 2003), whether chemical synaptic input can also regulate the strength of mammalian selleck electrical synapses in the long term remains

unclear. The electrically coupled neurons of the inferior olive represent a particularly attractive system for attacking this question. Electrical coupling is mediated by Connexin 36 gap junctions formed between dendritic spines of neighboring olivary cells (Long et al., 2002). Importantly, the gap junctions are located in close proximity to glutamatergic and GABAergic synapses housed within a glomerular structure (Llinas these et al., 1974, Sotelo et al., 1974, de Zeeuw et al., 1989, de Zeeuw et al., 1990a and de Zeeuw et al., 1990b): an anatomical arrangement that provides an excellent substrate for intersynaptic interaction. While fast, short-term modulation of olivary electrical coupling by both GABAergic and glutamatergic synaptic

inputs has long been suggested (Llinás, 1974, De Zeeuw et al., 1998, Lang, 2002, Jacobson et al., 2008, Hoge et al., 2011 and Bazzigaluppi et al., 2012), no direct evidence exists to support long-term modulation of electrical synapses in the mammalian inferior olive. Here we have addressed this question by performing simultaneous patch-clamp recordings between coupled neighboring olivary neurons. We demonstrate robust, long-term depression of electrical coupling triggered by physiological patterns of glutamatergic synaptic input. We obtained simultaneous recordings from electrically coupled pairs of olivary neurons in the principal olive and medial accessory olives in rat brainstem slices. Electrical coupling was measured by injecting negative current pulses into either cell (Devor and Yarom, 2002 and Landisman and Connors, 2005) and assessing the resulting voltage change in the noninjected cell. Coupling was detected between almost all neighboring neurons (with a coupling probability higher than 80%). The mean coupling coefficient was 0.

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