Excitation of Cerebellar Interneurons by Group I Metabotropic Glutamate Receptors

• Published in: Journal of neurophysiology Vol. 92; no. 3; pp. 1558 - 1565
• Main Authors: Karakossian, Movses H, Otis, Thomas S
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.09.2004
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Benzoates - pharmacology; Cerebellum - drug effects; Cerebellum - physiology; Glycine - analogs & derivatives; Glycine - pharmacology; In Vitro Techniques; Interneurons - drug effects; Interneurons - physiology; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate - agonists; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - physiology; Resorcinols - pharmacology
• DOI: 10.1152/jn.00300.2004
• ISSN: 0022-3077

Department of Neurobiology, University of California Medical Center, Los Angeles, California 90095-1763 Submitted 25 March 2004; accepted in final form 11 May 2004 Cerebellar basket and stellate neurons (BSNs) provide feed-forward inhibition to Purkinje neurons (PNs) and thereby play a principal role in determining the output of the cerebellar cortex. During low-frequency transmission, glutamate released at parallel fiber synapses excites BSNs by binding to AMPA receptors; high-frequency transmission also recruits N -methyl- D -aspartate (NMDA) receptors. We find that, in addition to these ligand-gated receptors, a G-protein–coupled glutamate receptor subtype participates in exciting BSNs. Stimulation of metabotropic glutamate receptor 1 (mGluR1 ) with the mGluR agonist ( RS )-3,5-dihydroxyphenylglycine (DHPG) leads to an increase in spontaneous firing of BSNs and indirectly to an increase in the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) recorded in PNs. Under conditions in which ligand-gated glutamate receptors are blocked, parallel fiber stimulation generates a slow excitatory postsynaptic current (EPSC) in BSNs that is inhibited by mGluR1 -selective antagonists. This slow EPSC is capable of increasing BSN spiking and indirectly increasing sIPSCs frequency in PNs. Our findings reinforce the idea that distinct subtypes of glutamate receptors are activated in response to different patterns of activity at excitatory synapses. The results also raise the possibility that mGluR1 -dependent forms of synaptic plasticity may occur at excitatory inputs to BSNs. Address for reprint requests and other correspondence: T. S. Otis, Dept. of Neurobiology, UCLA Medical Center, 650 Charles Young Dr., Box 951763, Los Angeles, CA 90095-1763 (E-mail: otist{at}ucla.edu ).