Diversity of cellular physiology and morphology of Purkinje cells in the adult zebrafish cerebellum. Issue 3 (1st December 2022)

• Record Type: Journal Article
• Authors: Magnus, Gerhard; Xing, Junling; Zhang, Yueping; Han, Victor Z.
• Is Part Of: Journal of comparative neurology. Volume 531:Issue 3(2023)
• Page Start: 461
• Page End: 485
• Publication Date: 2022-12-01
• Subjects: adult zebrafish -- cerebellum -- climbing fiber -- eurydendroid cells -- parallel fiber -- Purkinje cell morphology -- Purkinje cell spikes; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.25435
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: This study was designed to explore the functional circuitry of the adult zebrafish cerebellum, focusing on its Purkinje cells and using whole‐cell patch recordings and single cell labeling in slice preparations. Following physiological characterizations, the recorded single cells were labeled for morphological identification. It was found that the zebrafish Purkinje cells are surprisingly diverse. Based on their physiology and morphology, they can be classified into at least three subtypes: Type I, a narrow spike cell, which fires only narrow Na + spikes (<3 ms in duration), and has a single primary dendrite with an arbor restricted to the distal molecular layer; Type II, a broad spike cell, which fires broad Ca 2+ spikes (5–7 ms in duration) and has a primary dendrite with limited branching in the inner molecular layer and then further radiates throughout the molecular layer; and Type III, a very broad spike cell, which fires very broad Ca 2+ spikes (≥10 ms in duration) and has a dense proximal dendritic arbor that is either restricted to the inner molecular layer (Type IIIa), or radiates throughout the entire molecular layer (Type IIIb). The graded paired‐pulse facilitation of these Purkinje cells' responses to parallel fiber activations and the all‐or‐none, paired‐pulse depression of climbing fiber activation are largely similar to those reported for mammals. The labeled axon terminals of these Purkinje cells end locally, as reported for larval zebrafish. The present study provides evidence that the corresponding functional circuitry and information processing differ from what has been well‐established in the mammalian cerebellum. Abstract : Simplified local circuitry of the zebrafish cerebellum based on our results. Four subtypes of Purkinje cells (Type I, II, IIIa, and IIIb) were identified based on the patterns of their dendritic arbors. Their physiology was also variable, but distinguishable from that of nearby eurydendroid cells. All subtypes of Purkinje cells receive parallel fiber (PF) inputs but in a selective manner. While Type II, IIIa, and IIIb cells respond to climbing fiber (CF) activation, it is uncertain whether Type I cells receive CF input. Like the Type I Purkinje cells, eurydendroid cells respond to PF, but not to CF activation. Thus, the zebrafish cerebellar cortex may perform different computations according to its diverse Purkinje cell subtypes, hence requiring a reevaluation of the learning rules expressed in its circuitry.