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An evaluation of the synapse specificity of long‐term depression induced in rat cerebellar slices
Author(s) -
Reynolds T.,
Hartell N. A.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00563.x
Subject(s) - excitatory postsynaptic potential , stimulation , neuroscience , postsynaptic potential , pairing , stimulus (psychology) , long term potentiation , long term depression , chemistry , depolarization , inhibitory postsynaptic potential , physics , psychology , medicine , nmda receptor , receptor , ampa receptor , biochemistry , superconductivity , quantum mechanics , psychotherapist
1 Whole‐cell excitatory postsynaptic currents (EPSCs) were recorded from single Purkinje cells (PCs) in rat cerebellar slices in response to alternate activation of two separate sets of parallel fibres (PF 1 and PF 2 ). Pairing the stimulation of one input (PF 1 ) with PC depolarisation at 1 Hz for 5 min produced varied effects, including a long‐term depression (LTD) of subsequent responses, a medium‐term potentiation, or no change relative to baseline levels ( n = 14 ). In all but two cases PF 2 responses mirrored those in PF 1 , in both direction and magnitude even though this second pathway was not specifically activated during pairing. 2 Increasing the stimulus strength to evoke larger amplitude EPSCs (> 1000 pA) dramatically increased the proportion of cells that underwent LTD in both PF 1 and PF 2 . LTD in both pathways was postsynaptic calcium dependent. PC depolarisation alone ( n = 7 ) or PF 1 stimulation paired with PC hyperpolarisation ( n = 6 ) failed to induce LTD at either site. 3 Pairing PF 1 stimulation with climbing fibre (CF) activation at 1 Hz for 5 min produced LTD in the majority of cells regardless of the strength of PF stimulation. LTD under these conditions was not, however, input specific, even at the lowest stimulus strengths. 4 With EPSCs greater than 1000 pA in amplitude, depression was apparent in both pathways even when the duration of PF 1 pairing with depolarisation was limited to 1 min. Full expression of LTD in PF 2 required stimulation of this pathway to be resumed within a distinct temporal window of conjunctive pairing with PF 1 . Introducing a delay of 20 min before resumption of PF 2 activation preserved the input specificity of synaptic depression. 5 We conclude that pairing either PC depolarisation or CF activation with stimulation of a discrete set of PFs produces LTD that spreads to adjacent synapses on the same PC.