Presynaptic GABAB receptors modulate IPSPs evoked in neurons of deep cerebellar nuclei in vitro

Mouginot, Didier; Gähwiler, Beat H.

doi:10.1152/jn.1996.75.2.894

Cited by 22 publications

(17 citation statements)

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“…Furthermore, our results indicate that these properties differ from those of the synapses made between PCs and their target neurons at the DCN. We find that PC-PC synapses facilitate for short interpulse intervals, whereas the paired-pulse ratio for PC-DCN synapses is close to 1 in organotypic cultures (23,24), and the synapse is strongly depressing in acute slices from rats (25) and mice (26,27). Concerning train behavior, PC-DCN synapses show moderate (23) or substantial (26,27) depression during trains, which contrasts with the summating response to trains found in the present work (Fig.…”

Section: Discussioncontrasting

confidence: 57%

Recurrent axon collaterals underlie facilitating synapses between cerebellar Purkinje cells

Orduz

Llano

2007

Proc. Natl. Acad. Sci. U.S.A.

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Morphological studies have provided ample evidence for synaptic connections between cerebellar Purkinje cells (PCs), but the functional properties of these synapses remain elusive. We report on direct recordings of synaptically connected PCs in mice cerebellar slices. In PCs filled with a fluorescent dye to aid axon visualization and postsynaptic target identification, presynaptic action potentials elicited unitary inhibitory postsynaptic currents in neighboring PCs in 10% of potential connections tested. In 11 pairs, postsynaptic currents had a delay onset of 1.62 ؎ 0.16 ms with respect to the presynaptic spike, a 10 -90% rise time of 2.20 ؎ 0.33 ms, and a monoexponential decay with a time constant of 13.3 ؎ 1.7 ms. Average values for peak current and variance-to-mean ratio were 55 ؎ 14 and 30 ؎ 3 pA, respectively. In contrast to the depressing nature of the synapse between PCs and deep cerebellar nuclei neurons, PC-PC synapses exhibited strong facilitation operating within a time window of a few milliseconds; paired-pulse ratios for 3-and 20-ms intervals were 1.79 ؎ 0.18 and 1.01 ؎ 0.14, respectively (n ‫؍‬ 6). The facilitation is of presynaptic nature because it is accompanied by a decrease in failure rate. Trains of action potentials evoked in presynaptic varicosities volume-averaged calcium transients whose peak increased 1.7-fold as the frequency increased from 50 to 166 Hz. We suggest that PC-PC synapses are tuned for high fidelity of transmission during bursts of PC activity and that their operation in the cerebellar circuit modulates synchronized PC firing.presynaptic calcium ͉ cerebellum ͉ synaptic plasticity ͉ GABA ͉ calcium binding protein M ore than a century has elapsed since classical anatomical studies by Golgi revealed a surprising feature of Purkinje cells (PCs), namely the formation by their axon collaterals of profuse ramifications along the parasagittal plane extending from the granule cell layer into the PC layer of the cerebellar cortex (reviewed in ref. 1). The nature of this cortical plexus has since been the subject of many studies. Ramon y Cajal (2), based on light microscopy of mammalian and bird cerebellum, suggested that PC axon collaterals terminate in PCs and in other neurons of the molecular layer. In rodents, more recent work has described the development of the plexus (3-5) and provided ultrastructural evidence for the synaptic nature of the contacts made by PC collaterals (refs. 6 and 7 and see review in ref. 1). For PC-PC synapses some uncertainty remains as to the cellular compartment targeted by the collaterals. In mice, synaptic boutons were found on PC dendrites but not over PC somata (6), whereas in rat both PC regions receive PC synapses and clusters of boutons occur over PC somata (7). The boutons are large, up to 3 m in diameter in adult mice, but quantification on the number of release sites per bouton is not available. A distinctive feature of PC-PC contacts is their wide synaptic cleft, 2-fold larger than the usual value of 125 Å (7).Despite the precocity and abund...

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Section: Discussioncontrasting

confidence: 57%

Recurrent axon collaterals underlie facilitating synapses between cerebellar Purkinje cells

Orduz

Llano

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…GABA binds to and mediates its effects via post-synaptic ionotropic GABA A receptors and pre-and post-synaptic metabotropic GABA B receptors 19,20. Whereas the GABA A receptors mediate fast responses, the GABA B receptors mediate slow responses.…”

Section: Introductionmentioning

confidence: 99%

“…A neuropathological study in 199620 revealed that GABA B receptors are present on the presynaptic terminals of Purkinje cells in the deep cerebellar nuclei. These anatomical structures have since been considered involved in the probable genesis of ET.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, several findings indicate that deep cerebellar nuclei neurons belong to the family of single cell oscillators, and have a pacemaker-like activity 20,25–28. Interestingly, in the case of deep cerebellar nuclei neurons, it has been shown that their pacemaker-like activity is under tonic control by the GABAergic input from Purkinje cells 20.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, in the case of deep cerebellar nuclei neurons, it has been shown that their pacemaker-like activity is under tonic control by the GABAergic input from Purkinje cells 20. Even more compelling is the demonstration that deep cerebellar nuclei neurons can impose their rhythmicity to their thalamic target neurons with highly regular patterns of activity 28…”

Section: Introductionmentioning

confidence: 99%

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