Developmental changes of GABA_B receptor mediated K⁺ current in cerebellar Purkinje cells of lobules 3, 9, and 10 in mouse slice

Abstract

Cerebellum consists of ten lobules in mice and some functional differences between lobules have been reported. In this study, we focused on the developmental changes (postnatal days from P7-8, P14-18, P19-24 to P35-38) of GABA_B receptor (GABA_BR) mediated K⁺ current between lobules 3, 9, and 10. We recorded from Purkinje cells in sagittal section by whole-cell patch clamp at -70 mV in the presence of AMPA and GABA_A receptor antagonists. Upon application of GABA_BR agonist, baclofen, an outward current was evoked in all three lobules and at all developmental stages. The current amplitude showed a bell-shaped developmental change in all three lobules and the amplitude in lobule 3 was smaller than those in lobules 9 and 10 at all developmental stages. We previously showed that a similar outward current was observed only in lobule 10 by tetanic simulation of molecular layer (ML) in the presence of metabotropic glutamate receptor antagonist to block slow EPSC. The amplitude of ML-stimulation evoked outward current in lobule 10 also showed a bell-shaped developmental change. These results suggests that GABA_BR mediated K⁺ current is not qualitatively different between lobules 3, 9 and 10 but is different quantitatively, implying that there is a difference in the extend of GABA_BR mediated inhibitory effect on Purkinje cells between lobules 3, 9, and 10 during development. [J Physiol Sci. 2008;58 Suppl:S127]