小脳ニューロンにおけるGABA(C)およびBDNF受容体を介す膜電流–スライスパッチ法による解析。

抄録

GABA^*(C) receptors have been identified in vertebrate retina and visual neurons. These novel GABA(C) receptors are Cl⁻ pores and have pharmacological properties distinct from those of GABA(A) receptors, namely, resistance to bicuculline and selective activation by cis-4-aminocrotonic acid (CACA). Interestingly, mRNAs of the GABA(C) receptors have also been found in cerebellar Purkinje neurons of the rat (Boue-Grabot et al, 1998: Rozzo et al, 2002). Using brain slices and patch-clamp techniques (J Neurophysiol 90, 3490-3500, 2003), the author has characterized whole-cell membrane currents induced by a specific GABA(C) agonist, CACA, in Purkinje neurons of the rat. CACA (100 microM)-induced currents showed relatively small amplitudes, slow rise times and equilibrium potential similar to those of Cl ions. The dose-response relation of CACA showed no saturation even at 400 microM. These properties suggest that the receptors involved are those of GABA(C) subtype, consistent with previous findings of the mRNAs present in Purkinje neurons. However, since the specificities of the agonists as well as the antagonists to GABA(C) receptors seem to be weaker than previously thought (ex; Wall, 2001), more detailed analyses of GABA(C) receptors in cerebellar neurons are needed. Also, properties of BDNF^**-induced rapid currents , as have recently been reported (Blum et al, 2002), in cerebellar neurons will be presented. (*GABA= γ-aminobutyric acid;　**BDNF=brain-derived neurotrophic factor) [Jpn J Physiol 54 Suppl:S143 (2004)]