Sagittal view of a Purkinje cell with symmetric dendritic tree from the anterior caudal lobe of the cerebellum of a mormyrid fish (Gnathonemus petersii). The cell was filled with neurobiotin in an in vitro slice preparation and tracer was revealed with red fluorescent dye. Nissl counterstaining is shown in green. The cell was photographed from a slice of 200 μm using a confocal laser scanning microscope. The cell body is located in the anterior border with the eminentia granularis anterior (upper right), and the axon was cut, probably projecting to the brainstem (for details see text). The dendritic tree is planar, extending for 500x700 μm in the sagittal plane, but only for 110 μm (optical thickness) medio‐laterally. Two smooth primary dendrites arise from the soma and give off secondary and tertiary branches irregularly in the molecular region. The dendrites become thinner and more spiny as they extend further from the cell body. J. Comp. Neurol. 509:1–22, 2008. © 2008 Wiley‐Liss, Inc.

The caudal lobe of the mormyrid cerebellum includes the anterior portion, which is associated with the lateral line and eighth nerve senses, and the posterior portion, which is associated with the electrosense. This study examines the physiology and morphology of cells in the anterior portion in slice preparations. Two subtypes of Purkinje cells, efferent cells and stellate cells, are described. Multipolar Purkinje cells are located in the central region of the lobe, with large, multipolar, spiny dendrites and locally ending axons. Small Purkinje cells are located along its anterior border with the eminentia granularis anterior (EGa), with spiny dendrites in the molecular region. Axons of some small Purkinje cells end locally, whereas axons of other such cells are cut at the surface of the slices, suggesting that they project outside the lobe. Efferent cells are also distributed along the border with EGa. These cells have thin, smooth dendrites in the molecular region, and their axons are cut at the sliced surface. Stellate cells have thin, smooth dendrites and locally terminating axons. Physiologically, all types of cells respond to parallel fiber activation, but only multipolar Purkinje cells showed characteristic all-or-none climbing fiber responses. Although the majority of Purkinje cells fire a single type of spikes at resting level, a subset of small Purkinje cells fire small, narrow and large, broad spikes. Thus, the anterior caudal lobe of the mormyrid cerebellum is different from the mammalian cerebellum in having different subtypes of Purkinje cells and local termination of many Purkinje cell axons.

Sagittal view of a Purkinje cell with symmetric dendritic tree from the anterior caudal lobe of the cerebellum of a mormyrid fish (Gnathonemus petersii). The cell was filled with neurobiotin in an in vitro slice preparation and tracer was revealed with red fluorescent dye. Nissl counterstaining is shown in green. The cell was photographed from a slice of 200 μm using a confocal laser scanning microscope. The cell body is located in the anterior border with the eminentia granularis anterior (upper right), and the axon was cut, probably projecting to the brainstem (for details see text). The dendritic tree is planar, extending for 500x700 μm in the sagittal plane, but only for 110 μm (optical thickness) medio‐laterally. Two smooth primary dendrites arise from the soma and give off secondary and tertiary branches irregularly in the molecular region. The dendrites become thinner and more spiny as they extend further from the cell body. J. Comp. Neurol. 509:1–22, 2008. © 2008 Wiley‐Liss, Inc.