Inhibitory synaptic currents in rat cerebellar Purkinje cells: modulation by postsynaptic depolarization

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Synaptic Plasticity

Background:

• Cerebellar Purkinje cells receive inhibitory GABAergic inputs from basket and stellate interneurones.
• These interneurones are located in the molecular layer and synapse onto different regions of the Purkinje cell.
• Understanding these inhibitory pathways is crucial for cerebellar function.

Purpose of the Study:

• To characterize the synaptic currents evoked by stimulating cerebellar interneurones.
• To investigate the effects of Purkinje cell depolarization on these inhibitory synaptic currents.
• To elucidate the presynaptic and postsynaptic mechanisms underlying changes in synaptic transmission.

Main Methods:

• Tight-seal whole-cell recording in voltage-clamped Purkinje cells.
• Extracellular stimulation of inhibitory interneurones in the molecular layer.
• Application of bicuculline and excitatory synapse blockers.
• Analysis of synaptic current kinetics, amplitude, and failures.

Main Results:

• Evoked synaptic currents exhibited a 3-4 ms latency and biexponential time course (1-3 ms rise, 7-13 ms decay).
• Depolarizing Purkinje cells induced an initial inhibition (presynaptic) followed by potentiation (postsynaptic) of synaptic currents.
• Inhibition phase lasted ~1 min, while potentiation decayed with a half-time of ~13 min.

Conclusions:

• Depolarization-induced inhibition of GABAergic input to Purkinje cells is primarily presynaptic.
• Depolarization-induced potentiation of these inputs is likely postsynaptic.
• These findings provide insights into the complex regulation of cerebellar Purkinje cell activity.