Activation of Metabotropic Glutamate Receptors Inhibits High-Voltage-Gated Calcium Channel Currents of Chicken Nucleus Magnocellularis Neurons

Yong Lu, Edwin W Rubel
2005 Journal of Neurophysiology  
Lu, Yong and Edwin W Rubel. Activation of metabotropic glutamate receptors inhibits high-voltage-gated calcium channel currents of chicken nucleus magnocellularis neurons. . Using whole cell patch-clamp recordings, we pharmacologically characterized the voltage-gated Ca 2ϩ channel (VGCC) currents of chicken nucleus magnocellularis (NM) neurons using barium as the charge carrier. NM neurons possessed both low-and high-voltage-activated Ca 2ϩ channel currents (HVA I Ba 2ϩ). The Ntype channel
more » ... er (-conotoxin-GVIA) inhibited more than half of the total HVA I Ba 2ϩ, whereas blockers of L-and P/Q-type channels each inhibited a small fraction of the current. Metabotropic glutamate receptor (mGluR)-mediated modulation of the HVA I Ba 2ϩ was examined by bath application of glutamate (100 M), which inhibited the HVA I Ba 2ϩ by an average of 16%. The inhibitory effect was dose dependent and was partially blocked by -conotoxin-GVIA, indicating that mGluRs modulate N and other type HVA I Ba 2ϩ. The nonspecific mGluR agonist, (1S,3R)-1-aminocyclopentane-1,3-dicarbosylic acid (1S,3R-ACPD), mimicked the inhibitory effect of glutamate on HVA I Ba 2ϩ. Group I-III mGluR agonists showed inhibition of the HVA current with the most potent being the group III agonist L(ϩ)-2-amino-4-phosphonobutyric acid. 1S,3R-ACPD (200 M) had no effect on K ϩ or Na ϩ currents. The firing properties of NM neurons were also not altered by 1S,3R-ACPD. We propose that the inhibition of VGCC currents by mGluRs limits depolarization-induced Ca 2ϩ entry into these highly active NM neurons and regulates their Ca 2ϩ homeostasis.
doi:10.1152/jn.00659.2004 pmid:15371493 fatcat:ke5l7ol2njbgbbfvkqyv2zsvs4