Chemogenetic stimulation of striatal projection neurons modulates responses to Parkinson’s disease therapy
Cristina Alcacer, … , Tim Fieblinger, Maria Angela Cenci
Cristina Alcacer, … , Tim Fieblinger, Maria Angela Cenci
Published January 23, 2017
Citation Information: J Clin Invest. 2017;127(2):720-734. https://doi.org/10.1172/JCI90132.
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Research Article Neuroscience

Chemogenetic stimulation of striatal projection neurons modulates responses to Parkinson’s disease therapy

Abstract

Parkinson’s disease (PD) patients experience loss of normal motor function (hypokinesia), but can develop uncontrollable movements known as dyskinesia upon treatment with L-DOPA. Poverty or excess of movement in PD has been attributed to overactivity of striatal projection neurons forming either the indirect (iSPNs) or the direct (dSPNs) pathway, respectively. Here, we investigated the two pathways’ contribution to different motor features using SPN type–specific chemogenetic stimulation in rodent models of PD (PD mice) and L-DOPA–induced dyskinesia (LID mice). Using the activatory Gq-coupled human M3 muscarinic receptor (hM3Dq), we found that chemogenetic stimulation of dSPNs mimicked, while stimulation of iSPNs abolished the therapeutic action of L-DOPA in PD mice. In LID mice, hM3Dq stimulation of dSPNs exacerbated dyskinetic responses to L-DOPA, while stimulation of iSPNs inhibited these responses. In the absence of L-DOPA, only chemogenetic stimulation of dSPNs mediated through the Gs-coupled modified rat muscarinic M3 receptor (rM3Ds) induced appreciable dyskinesia in PD mice. Combining D2 receptor agonist treatment with rM3Ds-dSPN stimulation reproduced all symptoms of LID. These results demonstrate that dSPNs and iSPNs oppositely modulate both therapeutic and dyskinetic responses to dopamine replacement therapy in PD. We also show that chemogenetic stimulation of different signaling pathways in dSPNs leads to markedly different motor outcomes. Our findings have important implications for the design of effective antiparkinsonian and antidyskinetic drug therapies.

Authors

Cristina Alcacer, Laura Andreoli, Irene Sebastianutto, Johan Jakobsson, Tim Fieblinger, Maria Angela Cenci

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Figure 1

Histomolecular and electrophysiological validation of hM3Dq.

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Histomolecular and electrophysiological validation of hM3Dq. (A-I) Photo...
(A-I) Photomicrographs were acquired from A2a-Cre transgenic mice injected intrastriatally with the AAV5-hSyn-DIO-hM3Dq-mCherry vector. (A) Low-magnification photograph shows mCherry expression (revealed with RFP antibody) throughout the caudate-putamen (dorsolateral striatum). (B) The transduced striatal region shows positive immunostaining for p-ERK after treatment with CNO (1 mg/kg). (C) Merged confocal photograph demonstrates regional colocalization of hM3Dq-mCherry and p-ERK. (D) High-magnification photomicrograph of a transduced area (cf. inset in A) reveals mCherry immunoreactivity in both neuropile and SPN somas (indicated by arrows). (E) p-ERK immunoreactivity in transduced SPNs after treatment with CNO. (F) Cellular colocalization of the 2 markers demonstrated by the merged confocal picture. (G-I) No p-ERK immunostaining was observed in transduced SPNs after vehicle treatment. Scale bars: 400 μm (A–C); 20 μm (D–I). (J and K) Electrophysiological response to CNO in hM3Dq- and EGFP-transduced dSPN and iSPN from D1-Cre and A2a-Cre intact mice. Whole-cell patch clamp recordings were made in ex vivo slices from SPNs transduced with hM3Dq or EGFP. (J) Bath application of CNO (10 μM) gradually increased the number of APs induced by brief somatic current pulses in both dSPNs and iSPNs transduced with hM3Dq, but no increase was observed in the control group. RM 2-way ANOVA (n = 7 cells per data set): effect of group, F(2, 18) = 15.80, P = 0.0001; time (effect of CNO), F(4, 72) = 11.29, P = 0.0001; interaction, F(8, 72) = 3.446, P = 0.0021. *P < 0.05; **P < 0.01 for the effect of CNO in dSPN-hM3Dq vs. dSPN-EGFP; ###P < 0.001 for the effect of CNO in iSPN-hM3Dq vs. dSPN-GFP. (K) Representative traces of AP responses to current injection, at baseline and after CNO application, in hM3Dq-transduced dSPNs and iSPNs and an EGFP-transduced dSPN.