Molecular identification of the Lugaro cell in the cat cerebellar cortex

The cerebellar cortex contains five major classes of neurons that can be differentiated from one another on the basis of their location, size, shape, and, in some cases, molecular characteristics. The cerebellar cortex also contains other, less numerous neuronal types, including the Lugaro cell, which has been described on only a few occasions. The Lugaro cell is a relative rare cell type and is characterized by a fusiform cell body with thick, horizontally oriented dendrites. It is located in or slightly below the Purkinje cell layer. Because the Lugaro cell shares some morphological characteristics with the other large granular layer neurons, it often has been classified as a Golgi cell. In the present study we have taken advantage of differences in the molecular properties of neurons and have used monoclonal antibodies to identify and classify the Lugaro cell. Three large neuronal types in the cerebellar cortex were examined with cell-type-specific antibodies: Cat-301 and Cat-304 for Lugaro cells; Rat-303 for Golgi cells; and anti-calbindin for Purkinje cells. Double label immunocytochemistry on sections of the cat cerebellum was performed with subclass- or species-specific secondary antibodies. Each of the three antibodies was selective for one of the three large neuron classes. Cat-301 and Cat-304 recognized Lugaro cells but not Golgi or Purkinje cells. Our results demonstrate that the Lugaro cells are molecularly, as well as morphologically, distinct from Purkinje and Golgi cells and thus constitute a distinct cell type in the cerebellar cortex.