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Not GABA But Glycine Mediates Segmental, Propriospinal, and Bulbospinal Postsynaptic Inhibition in Adult Mouse Spinal Forelimb Motor Neurons
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
2015 (English)In: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 35, no 5, 1991-1998 p.Article in journal (Refereed) Published
Abstract [en]

The general view is that both glycine (Eccles, 1964) and GABA (Curtis and Felix, 1971) evoke postsynaptic inhibition in spinal motor neurons. In newborn or juvenile animals, there are conflicting results showing postsynaptic inhibition in motor neurons by corelease of GABA and glycine (Jonas et al., 1998) or by glycine alone (Bhumbra et al., 2012). To resolve the relative contributions of GABA and glycine to postsynaptic inhibition, we performed in vivo intracellular recordings from forelimb motor neurons in adult mice. Postsynaptic potentials evoked from segmental, propriospinal, and bulbospinal systems in motor neurons were compared across four different conditions: control, after gabazine, gabazine followed by strychnine, and strychnine alone. No significant differences were observed in the proportion of IPSPs and EPSPs between control and gabazine conditions. In contrast, EPSPs but not IPSPs were recorded after adding strychnine with gabazine or administering strychnine alone, suggesting an exclusive role for glycine in postsynaptic inhibition. To test whether the injected (intraperitoneal) dose of gabazine blocked GABAergic inhibitory transmission, we evoked GABA(A) receptor-mediated monosynaptic IPSPs in deep cerebellar nuclei neurons by stimulation of Purkinje cell fibers. No monosynaptic IPSPs could be recorded in the presence of gabazine, showing the efficacy of gabazine treatment. Our results demonstrate that, in the intact adult mouse, the postsynaptic inhibitory effects in spinal motor neurons exerted by three different systems, intrasegmental and intersegmental as well as supraspinal, are exclusively glycinergic. These findings emphasize the importance of glycinergic postsynaptic inhibition in motor neurons and challenge the view that GABA also contributes.

Place, publisher, year, edition, pages
2015. Vol. 35, no 5, 1991-1998 p.
Keyword [en]
adult, GABA, glycine, inhibition, motor neuron, mouse
National Category
URN: urn:nbn:se:umu:diva-100954DOI: 10.1523/JNEUROSCI.1627-14.2015ISI: 000349671100015PubMedID: 25653357OAI: diva2:796688
Available from: 2015-03-20 Created: 2015-03-16 Last updated: 2015-03-20Bibliographically approved

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