Short-term facilitation and depression in the cerebellum: some observations on wild-type and mutant rodents deficient in the extracellular matrix molecule tenascin C.
Short-term plasticity was studied on synapses to Purkinje cells (PC): paired-pulse facilitation in parallel fibers (PF) and paired-pulse depression in climbing fibers (CF). Both phenomena relate to synaptic strength. These forms of short-term plasticity were tested on cerebellar slices in rat by early postnatal synchronous stimulation of olivary neurons (i.e., CFs) with harmaline and by inhibition of a metabotropic glutamate receptor (mGluR) as well as in mice that were deficient in the extracellular matrix glycoprotein tenascin-C. Harmaline stimulation delayed the developmental competition between CF inputs and maintained multiple innervation. Paired-pulse depression of the CF-PC synapse after harmaline treatment was more expressed. However, paired-pulse facilitation in PF-PC synapses remained unchanged. Electrophysiological responses of postsynaptic mGluR1 in CF-PC synapses could be obtained only with AMPA receptors blocked and glutamate uptake impaired. The mGluR1-specific antagonist CPCCOEt suppressed the CF-mGluR EPSC in some PCs and potentiated it in other PCs. CF paired-pulse depression was not changed with CPCCOEt, thus excluding a presynaptic effect. The postsynaptic effect was underlined by CPCCOEt-induced rise in amplitude of EPSC and by a prolongation of its decay time. Tenascins are extracellular matrix glycoproteins that may restrict the regenerative capacity of the nervous tissue. Testing short-term presynaptic plasticity in tenascin-C-deficient mice showed that CF paired-pulse depression was less expressed while PF paired-pulse facilitation was augmented except in a group of cells where there was even depression. The results underline differences in forms of short-term plasticity with regard to susceptibility to diverse modulatory factors.
Andjus
Pavle R
PR
Department for Neuroscience, University of Turin, Italy.
Bajić
Aleksandar
A
Zhu
Lan
L
Schachner
Melitta
M
Strata
Piergiorgio
P
D000818:Animals; D002531:Cerebellum / Q000378:metabolism / Q000473:pathology*; D003866:Depressive Disorder / Q000378:metabolism / Q000473:pathology*; D004594:Electrophysiology; D016326:Extracellular Matrix Proteins / Q000172:deficiency / Q000378:metabolism*; D009154:Mutation; D009412:Nerve Fibers / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D011689:Purkinje Cells / Q000502:physiology; D051381:Rats; D011922:Rats, Mutant Strains; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D013569:Synapses / Q000502:physiology; D019063:Tenascin / Q000172:deficiency / Q000378:metabolism*
D016326:Extracellular Matrix Proteins; D018094:Receptors, Metabotropic Glutamate; D019063:Tenascin