HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 563/2/443    most recent jphysiol.2004.081000v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tabata, T. Articles by Kano, M. Search for Related Content PubMed PubMed Citation Articles by Tabata, T. Articles by Kano, M.

¹ Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan
² Faculty of Pharmaceutical Sciences, Kanazawa University, Kanazawa, Ishikawa 920-0934, Japan

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 -aminobutyric acid receptors (GABA_BR) that are assumed to mediate major responses, including postsynaptic modulation of the synaptic inputs. However, the identity and function of effectors operated by GABA_BR are not fully elucidated. Here we characterized an inwardly rectifying current activated by baclofen (I_bacl), a GABA_BR agonist, in cultured mouse Purkinje cells using a ruptured-patch whole-cell technique. I_bacl is operated by GABA_BR via G_i/o-proteins, as it is not inducible in pertussis-toxin-pretreated cells. I_bacl is carried by K⁺ because its reversal potential shifts with the equilibrium potential of K⁺. I_bacl is blocked by 10^–3 M Ba²⁺ or Cs⁺, and 10^–8 M tertiapin-Q. Upon the onset and offset of a hyperpolarizing step, I_bacl 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 I_bacl. Perforated-patch recordings from cultured Purkinje cells demonstrate that I_bacl 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 I_bacl impedes spontaneous firing. Therefore, I_bacl may reduce the postsynaptic and intrinsic excitability of Purkinje cells under physiological conditions. These findings give a new insight into the role of GABA_BR signalling in cerebellar information processing.

(Received 11 December 2004; accepted after revision 4 January 2005; first published online 6 January 2005)
Corresponding author M. Kano: Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan. Email: mkano{at}med.kanazawa-u.ac.jp

This article has been cited by other articles:

				Y. Kamikubo, T. Tabata, S. Kakizawa, D. Kawakami, M. Watanabe, A. Ogura, M. Iino, and M. Kano Postsynaptic GABAB receptor signalling enhances LTD in mouse cerebellar Purkinje cells J. Physiol., December 1, 2007; 585(2): 549 - 563. [Abstract] [Full Text] [PDF]

				T. Tabata, D. Kawakami, K. Hashimoto, H. Kassai, T. Yoshida, Y. Hashimotodani, B. B. Fredholm, Y. Sekino, A. Aiba, and M. Kano G protein-independent neuromodulatory action of adenosine on metabotropic glutamate signalling in mouse cerebellar Purkinje cells J. Physiol., June 1, 2007; 581(2): 693 - 708. [Abstract] [Full Text] [PDF]