Distribution of glycine receptors on the surface of the mature calyx of Held nerve terminal

08.10.2014

Trojanova J, Kulik A, Janacek J, Kralikova M, Syka J, Turecek R

Front Neural Circuits. 2014;8:120

Front Neural Circuits        online article

In axonal terminals of the central neurons glycine receptors (GlyRs) trigger a slow facilitation of presynaptic transmitter release. In this study, we examined the distribution of GlyRs in the rat calyx of Held nerve terminal using pre-embedding immunoelectron microscopy. We performed a quantitative analysis of GlyR-associated immunogold (IG) labeling in 3D reconstructed segments. A variable density of IG particles and their accumulations indicated a non-uniform distribution of the receptors in the calyx. Increased densities of IG particles were found in calyceal swellings. In swellings and stalks, IG particles did not tend to accumulate near the glutamate releasing zones. On the other hand, GlyRs in swellings preferentially occupied membrane regions unconnected to postsynaptic cells accessible by glycine. Sites with increased GlyR concentrations were found tightly juxtaposed with GABA/glycinergic nerve endings. These support the concept of an idirect mechanism underlying the modulatory effects of GlyRs, activated by glycine spillover. There is an activity-dependent mechanism regulating the surface distribution of GlyRs in axonal terminals of central neurons.