Membrane excitability of Purkinje cells in the vestibulocerebellum

Abstract

Introduction: Cerebellar Purkinje cells (PCs) are the sole output of the cerebellar cortex, and function as key to a variety of learning-related behavior by integrating multimodal afferent inputs. Intrinsic membrane excitability of neuron determines the input-output relationship, and therefore governs the functions of neural circuits. Cerebellar vermis consists of ten lobules (lobule I-X), and each lobule receives different sensory information. However, lobule-specific differences of electrophysiological properties of PC are incompletely understood. Methods: To address this question, we performed a systematic comparison of membrane properties of PCs from different lobules (lobules III-V vs. X) using patch-clamp technique. Results: Two types of firing patterns (tonic firing and complex bursting) were identified in response to depolarizing current injections in lobule III-V PCs, whereas four distinct firing patterns (tonic firing, complex bursting, initial bursting and gap firing) were observed in lobule X. A-type K+ current and early inactivation of fast Na+ conductance with activation of 4-aminopyridine sensitive conductances were shown to be responsible for the formation of gap firing and initial bursting patterns, respectively, which were observed only in lobule X. In response to current injection, PCs in lobule X spiked with wider dynamic range. Conclusions: These differences in firing pattern and membrane properties probably contribute to signal processing of afferent inputs in lobule-specific fashion, and particularly diversity of discharge patterns in lobule X, as a part of vestibulocerebellum, might be involved in strict coordination of a precise temporal response to a wide range of head movements.