Bidirectional interactions between H-channels and Na+-K + pumps in mesencephalic trigeminal neurons Journal Article


Author(s): Kang, Youngnam; Notomi, Takuya; Saito, Mitsuru; Zhang, Wei; Shigemoto, Ryuichi
Article Title: Bidirectional interactions between H-channels and Na+-K + pumps in mesencephalic trigeminal neurons
Affiliation
Abstract: The Na+-K+ pump current (Ip) and the h-current (Ih) flowing through hyperpolarization-activated channels (h-channels) participate in generating the resting potential. These two currents are thought to be produced independently. We show here bidirectional interactions between Na+-K+ pumps and h-channels in mesencephalic trigeminal neurons. Activation of Ih leads to the generation of two types of ouabain-sensitive Ip with temporal profiles similar to those of instantaneous and slow components of I h, presumably reflecting Na+ transients in a restricted cellular space. Moreover, the Ip activated by instantaneous I h can facilitate the subsequent activation of slow Ih. Such counteractive and cooperative interactions were also disclosed by replacing extracellular Na+ with Li+, which is permeant through h-channels but does not stimulate the Na+-K+ pump as strongly as Na+ ions. These observations indicate that the interactions are bidirectional and mediated by Na+ ions. Also after substitution of extracellular Na+ with Li+, the tail Ih was reduced markedly despite an enhancement of Ih itself, attributable to a negative shift of the reversal potential for I h presumably caused by intracellular accumulation of Li+ ions. This suggests the presence of a microdomain where the interactions can take place. Thus, the bidirectional interactions between Na+-K + pumps and h-channels are likely to be mediated by Na+ microdomain. Consistent with these findings, hyperpolarization-activated and cyclic nucleotide-modulated subunits (HCN1/2) and the Na+-K + pump α3 isoform were colocalized in plasma membrane of mesencephalic trigeminal neurons having numerous spines.
Keywords: Bidirectional interactions; Excitability; H-channel; Mesencephalic trigeminal neurons; Microdomain; Na+-K+ pump; Na+-transient; Spines
Journal Title: Journal of Neuroscience
Volume: 24
Issue 14
ISSN: 1529-2401
Publisher: Society for Neuroscience  
Date Published: 2004-04-07
Start Page: 3694
End Page: 3702
DOI: 10.1523/JNEUROSCI.5641-03.2004
Open access: no