Browsing by Subject "Glycine receptor"

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    High ethanol sensitive glycine receptors regulate firing in D1 medium spiny neurons in the nucleus Accumbens
    (Elsevier, 2019-12-01) Gallegos, S.; Muñoz, B.; Araya, A.; Aguayo, L.G.; Psychiatry, School of Medicine
    Inhibitory glycine receptors (GlyRs) are widely expressed in spinal cord and brain stem. They are also expressed in the nucleus Accumbens (nAc) where they have been implicated in the release of dopamine from the ventral tegmental area to the nAc in the presence of ethanol. One of the major types of neurons in the nAc are the Dopamine 1 receptor-expressing (D1+) medium spiny neurons (MSNs) that are activated when addictive drugs, like ethanol, are administrated. Thus, D1(+) MSNs are a relevant target for the study of ethanol effects. Here, using electrophysiological recordings, we report that GlyRs in D1(+) MSNs are highly sensitive to ethanol, with potentiation starting at 5 mM (26 ± 5%). Single channel recordings in D1(+) MSNs showed that 10 mM ethanol increased the open probability of the channel (0.22 ± 0.05 versus 0.66 ± 0.16), but did not affect channel conductance (~40 pS). A glycinergic mediated tonic current in D1(+) MSNs was potentiated by 10 and 50 mM ethanol causing a reduction in the excitability of these cells. A 34 ± 7% reduction in action potential firing was observed in these neurons in the presence of 50 mM ethanol. Interestingly, no effects of ethanol were detected in the presence of strychnine or in D1(-) MSNs in the nAc. These results indicate that GlyRs present in D1(+) MSNs are sensitive to low concentrations of ethanol, and that potentiation of this inhibitory current regulates the activation of nAc, acting as a homeostatic signal that would prevent over-activation of the reward system when drugs like ethanol are consumed.
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    Modulatory Actions of the Glycine Receptor β Subunit on the Positive Allosteric Modulation of Ethanol in α2 Containing Receptors
    (Frontiers Media, 2021-11-18) Muñoz, Braulio; Mariqueo, Trinidad; Murath, Pablo; Peters, Christian; Yevenes, Gonzalo E.; Moraga-Cid, Gustavo; Peoples, Robert W.; Aguayo, Luis G.; Pharmacology and Toxicology, School of Medicine
    Alpha1-containing glycine receptors (GlyRs) are major mediators of synaptic inhibition in the spinal cord and brain stem. Recent studies reported the presence of α2-containing GlyRs in other brain regions, such as nucleus accumbens and cerebral cortex. GlyR activation decreases neuronal excitability associated with sensorial information, motor control, and respiratory functions; all of which are significantly altered during ethanol intoxication. We evaluated the role of β GlyR subunits and of two basic amino acid residues, K389 and R390, located in the large intracellular loop (IL) of the α2 GlyR subunit, which are important for binding and functional modulation by Gβγ, the dimer of the trimeric G protein conformation, using HEK-293 transfected cells combined with patch clamp electrophysiology. We demonstrate a new modulatory role of the β subunit on ethanol sensitivity of α2 subunits. Specifically, we found a differential allosteric modulation in homomeric α2 GlyRs compared with the α2β heteromeric conformation. Indeed, while α2 was insensitive, α2β GlyRs were substantially potentiated by ethanol, GTP-γ-S, propofol, Zn2+ and trichloroethanol. Furthermore, a Gβγ scavenger (ct-GRK2) selectively attenuated the effects of ethanol on recombinant α2β GlyRs. Mutations in an α2 GlyR co-expressed with the β subunit (α2AAβ) specifically blocked ethanol sensitivity, but not propofol potentiation. These results show a selective mechanism for low ethanol concentration effects on homomeric and heteromeric conformations of α2 GlyRs and provide a new mechanism for ethanol pharmacology, which is relevant to upper brain regions where α2 GlyRs are abundantly expressed.