Contrasting actions of group I metabotropic glutamate receptors in distinct mouse striatal neurones.
In mouse striatum, metabotropic glutamate receptor (mGluR) activation leads to several modulatory effects in synaptic transmission. These effects range from dampening of glutamate release from excitatory terminals to depolarization of divergent classes of interneurones. We compared the action of group I mGluR activation on several populations of striatal neurones using a combination of genetic identification, electrophysiology, and Ca(2+) imaging techniques. Patch-clamp recordings from spiny projection neurones (SPNs) and various interneurone populations demonstrated that the group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) robustly depolarizes several interneurone classes that form GABAergic synapses onto SPNs. We further utilized the genetic reporter mouse strain Ai38, which expresses the calcium indicator protein GCaMP3 in a Cre-dependent manner. Breeding Ai38 mice with various neurone selective, promoter-driven Cre recombinase mice resulted in GCaMP3 expression in defined cell populations in striatum. Consistent with our electrophysiological findings, group I agonist applications increased intracellular levels of calcium ([Ca(2+)]i) in all interneurone populations tested. We also found that acute DHPG application evoked a transient, rapid increase in [Ca(2+)]i from only a small percentage of identifiable SPNs. Surprisingly, this fast [Ca(2+)]i response exhibited a robust enhancement or sensitization, in a calcium-dependent fashion. Following several procedures to increase [Ca(2+)]i, the vast majority of SPNs responded with rapid changes in [Ca(2+)]i to mGluR agonists in a time-dependent fashion. These findings extend our understanding on group I mGluR influence of striatal output via powerful, local GABAergic connections in addition to [Ca(2+)]i dynamics that impact on activity or spike-timing-dependent forms of synaptic plasticity.
Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, 20007, USA Interdisciplinary Program in Neuroscience, Georgetown University School of Medicine, Washington, DC, 20007, USA jp374@georgetown.edu.
John G
JG
Partridge
Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, 20007, USA.
Amanda E
AE
Lewin
Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, 20007, USA.
Jessica R
JR
Yasko
Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, 20007, USA Interdisciplinary Program in Neuroscience, Georgetown University School of Medicine, Washington, DC, 20007, USA.
Stefano
S
Vicini
D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism*; D059330:GABAergic Neurons / Q000378:metabolism* / Q000502:physiology; D007395:Interneurons / Q000378:metabolism* / Q000502:physiology; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism / Q000502:physiology
D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D008734:Methoxyhydroxyphenylglycol; C010117:3,4-dihydroxyphenylglycol