Impaired striatal D2 receptor function leads to enhanced GABA transmission in a mouse model of DYT1 dystonia.

Abstract

DYT1 dystonia is caused by a deletion in a glutamic acid residue in the C-terminus of the protein torsinA, whose function is still largely unknown. Alterations in GABAergic signaling have been involved in the pathogenesis of dystonia. We recorded GABA- and glutamate-mediated synaptic currents from a striatal slice preparation obtained from a mouse model of DYT1 dystonia. In medium spiny neurons (MSNs) from mice expressing human mutant torsinA (hMT), we observed a significantly higher frequency, but not amplitude, of GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs) and miniature currents (mIPSCs), whereas glutamate-dependent spontaneous excitatory synaptic currents (sEPSCs) were normal. No alterations were found in mice overexpressing normal human torsinA (hWT). To identify the possible sources of the increased GABAergic tone, we recorded GABAergic Fast-Spiking (FS) interneurons that exert a feed-forward inhibition on MSNs. However, both sEPSC and sIPSC recorded from hMT FS interneurons were comparable to hWT and non-transgenic (NT) mice. In physiological conditions, dopamine (DA) D2 receptor act presynaptically to reduce striatal GABA release. Of note, application of the D2-like receptor agonist quinpirole failed to reduce the frequency of sIPSCs in MSNs from hMT as compared to hWT and NT mice. Likewise, the inhibitory effect of quinpirole was lost on evoked IPSCs both in MSNs and FS interneurons from hMT mice. Our findings demonstrate a disinhibition of striatal GABAergic synaptic activity, that can be at least partially attributed to a D2 DA receptor dysfunction.

• Authors: Giuseppe Sciamanna, Paola Bonsi, Annalisa Tassone, Dario Cuomo, Anne Tscherter, Maria Teresa Viscomi, Giuseppina Martella, Nutan Sharma, Giorgio Bernardi, David G Standaert, Antonio Pisani
• Journal: Neurobiology of disease (Neurobiol Dis) Vol. 34 Issue 1 Pg. 133-45 (Apr 2009) ISSN: 1095-953X [Electronic] United States
• PMID: 19187797 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Molecular Chaperones
• Receptors, Dopamine D2
• TOR1A protein, human
• Glutamic Acid
• gamma-Aminobutyric Acid

Topics

• Analysis of Variance
• Animals
• Disease Models, Animal
• Dystonic Disorders (physiopathology)
• Excitatory Postsynaptic Potentials
• Glutamic Acid (metabolism)
• Humans
• In Vitro Techniques
• Inhibitory Postsynaptic Potentials
• Mice
• Mice, Transgenic
• Miniature Postsynaptic Potentials
• Molecular Chaperones (genetics, metabolism)
• Neurons (physiology)
• Patch-Clamp Techniques
• Receptors, Dopamine D2 (metabolism)
• Synaptic Transmission (physiology)
• gamma-Aminobutyric Acid (metabolism)