Present address: Department of Neurobiology, University of Chicago, Abbott 317, 947 E. 58th Street, MC0928 Chicago, IL 60637, USA.
Bidirectional plasticity at developing climbing fiber–Purkinje neuron synapses
Article first published online: 21 NOV 2008
© The Authors (2008). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 28, Issue 12, pages 2393–2400, December 2008
How to Cite
Ohtsuki, G. and Hirano, T. (2008), Bidirectional plasticity at developing climbing fiber–Purkinje neuron synapses. European Journal of Neuroscience, 28: 2393–2400. doi: 10.1111/j.1460-9568.2008.06539.x
- Issue published online: 9 DEC 2008
- Article first published online: 21 NOV 2008
- Received 5 November 2007, revised 14 October 2008, accepted 15 October 2008
- long-term depression;
- long-term potentiation;
- presynaptic mechanism
Climbing fibers provide one of the two major excitatory inputs to the cerebellar cortex. In an immature animal, several climbing fibers form synapses with one Purkinje neuron. During postnatal development most climbing fiber innervations with a Purkinje neuron are eliminated and only one strong fiber remains. Previous studies suggested that this pruning of surplus climbing fiber innervations depends on the neuronal activity. We hypothesized that synaptic plasticity might play a role in the maturation and refinement of such a climbing fiber projection pattern, and examined the plasticity properties of synapses between postnatal days 5 and 9 in mice. We found that a 5 Hz conditioning stimulation of climbing fibers forming relatively strong synapses with a Purkinje neuron induced long-term potentiation of the transmission accompanied by a decrease in the paired-pulse ratio of excitatory postsynaptic current amplitudes. This was suggestive of an increased probability of presynaptic release. However, the conditioning stimulation of climbing fibers forming relatively weak synapses induced long-term depression and tended to increase the paired-pulse ratio. Thus, the direction of plasticity appears to be determined by the strength of synaptic connection. Long-term depression occurred only in the conditioned climbing fiber, whereas long-term potentiation spread to unconditioned climbing fibers. A postsynaptic increase in the intracellular Ca2+ concentration was required for long-term potentiation but not for long-term depression. These results reveal the existence of novel presynaptic plasticity at immature climbing fiber–Purkinje cell synapses, which may contribute to the maturation and refinement of the climbing fiber projection pattern.