Hisako Nakayama
   Department   School of Medicine, School of Medicine
   Position   Associate Professor
Article types Original article
Language English
Peer review Peer reviewed
Title GABAergic activation of an inwardly rectifying K+ current in mouse cerebellar Purkinje cells.
Journal Formal name：The Journal of physiology
Abbreviation：J Physiol
ISSN code：00223751/14697793
Domestic / ForeginForegin
Volume, Issue, Page 563(Pt 2),pp.443-457
Author and coauthor TABATA Toshihide†, HARUKI Shigeki†, NAKAYAMA Hisako, KANO Masanobu*
Publication date 2005/03
Summary Cerebellar Purkinje cells integrate motor information conveyed by excitatory synaptic inputs from parallel and climbing fibres. Purkinje cells abundantly express B-type G-protein-coupled γ-aminobutyric acid receptors (GABABR) that are assumed to mediate major responses, including postsynaptic modulation of the synaptic inputs. However, the identity and function of effectors operated by GABABR are not fully elucidated. Here we characterized an inwardly rectifying current activated by baclofen (Ibacl), a GABABR agonist, in cultured mouse Purkinje cells using a ruptured-patch whole-cell technique. Ibacl is operated by GABABR via Gi/o-proteins, as it is not inducible in pertussis-toxin-pretreated cells. Ibacl is carried by K+ because its reversal potential shifts with the equilibrium potential of K+. Ibacl is blocked by 10−3m Ba2+ or Cs+, and 10−8m tertiapin-Q. Upon the onset and offset of a hyperpolarizing step, Ibacl is activated and deactivated, respectively, with double-exponential time courses (time constants, <1 ms and 30–80 ms). Based on similarities in the above properties, G-protein-coupled inwardly rectifying K+ (GIRK) channels are thought to be responsible for Ibacl. Perforated-patch recordings from cultured Purkinje cells demonstrate that Ibacl hyperpolarizes the resting potential and the peak level achieved by glutamate-evoked potentials initiated in the dendrites. Moreover, cell-attached recordings from Purkinje cells in cerebellar slices demonstrate that Ibacl impedes spontaneous firing. Therefore, Ibacl may reduce the postsynaptic and intrinsic excitability of Purkinje cells under physiological conditions. These findings give a new insight into the role of GABABR signalling in cerebellar information processing.
DOI 10.1113/jphysiol.2004.081000
PMID 15637097