This study investigates the electrophysiological properties of Purkinje cell dendrites in mammalian cerebellar slices. The authors use intradendritic recording to explore the passive and active characteristics of these dendrites, focusing on ionic requirements for dendritic conductances. Key findings include: 1. **Dendritic Electresponsiveness**: Dendrites exhibit active electroresponsiveness, with dendritic action potentials conducted non-continuously and generated by voltage-dependent Na and Ca currents. 2. **Synaptic Potentials**: Climbing fiber activation in Purkinje cells produces all-or-none excitatory postsynaptic potentials (EPSPs) that generate a set of action potentials with a slower time course compared to somatic spikes. 3. **Input Resistance**: Intradendritic recordings show that input resistance is lower at the dendritic level compared to the soma, and the input resistance is TTX-insensitive. 4. **Calcium-Dependent Potentials**: Calcium plateau potentials and dendritic spike bursts are observed at the dendritic level, characterized by slow onset, large amplitude, and multiple spike components. These potentials are TTX-insensitive and blocked by Ca channel blockers. 5. **Sodium Conductance**: Sodium spikes are not actively generated in dendrites, and their amplitude decreases with increasing distance from the soma. 6. **Spontaneous Firing**: Spontaneous dendritic bursting is observed, likely induced by Ca currents, and is TTX-insensitive. 7. **Discussion**: The study highlights the differences in excitable properties between the soma and dendrites of Purkinje cells, suggesting that the soma has a sharp voltage-dependent Na conductance change, while the dendrites have a more prominent Ca conductance. The results provide insights into the functional properties of Purkinje cell dendrites and their role in synaptic transmission and neuronal function.This study investigates the electrophysiological properties of Purkinje cell dendrites in mammalian cerebellar slices. The authors use intradendritic recording to explore the passive and active characteristics of these dendrites, focusing on ionic requirements for dendritic conductances. Key findings include: 1. **Dendritic Electresponsiveness**: Dendrites exhibit active electroresponsiveness, with dendritic action potentials conducted non-continuously and generated by voltage-dependent Na and Ca currents. 2. **Synaptic Potentials**: Climbing fiber activation in Purkinje cells produces all-or-none excitatory postsynaptic potentials (EPSPs) that generate a set of action potentials with a slower time course compared to somatic spikes. 3. **Input Resistance**: Intradendritic recordings show that input resistance is lower at the dendritic level compared to the soma, and the input resistance is TTX-insensitive. 4. **Calcium-Dependent Potentials**: Calcium plateau potentials and dendritic spike bursts are observed at the dendritic level, characterized by slow onset, large amplitude, and multiple spike components. These potentials are TTX-insensitive and blocked by Ca channel blockers. 5. **Sodium Conductance**: Sodium spikes are not actively generated in dendrites, and their amplitude decreases with increasing distance from the soma. 6. **Spontaneous Firing**: Spontaneous dendritic bursting is observed, likely induced by Ca currents, and is TTX-insensitive. 7. **Discussion**: The study highlights the differences in excitable properties between the soma and dendrites of Purkinje cells, suggesting that the soma has a sharp voltage-dependent Na conductance change, while the dendrites have a more prominent Ca conductance. The results provide insights into the functional properties of Purkinje cell dendrites and their role in synaptic transmission and neuronal function.