Title

Postnatal Maturation of Gephyrin/Glycine Receptor Clusters on Developing Renshaw Cells

Document Type

Article

Publication Date

10-9-2000

Abstract

Adult mammalian Renshaw cells express large and complex postsynaptic gephyrin/glycine receptor clusters on their surface. Larger gephyrin clusters correlate with more “efficacious” inhibitory synapses, in terms of larger postsynaptic quantal size amplitudes, in part because they likely contain more postsynaptic receptors (Lim et al. [1999] J. Physiol. (Lond.) 516:505–512; Oleskevich et al. [1999] J. Neurophysiology 82:312–319). Here, we studied the postnatal development of the gephyrin/glycine receptor cluster size on Renshaw cells. Renshaw cells were identified by their calbindin immunoreactivity, location and morphology, and presence of cholinergic input. The populations of clusters over developing Renshaw cells immunoreactive to gephyrin or glycine receptor α1 subunits were comparable in number, size, and complexity and displayed a high degree of colocalization (>90%) at all ages. Quantitative morphologic analysis was performed on gephyrin-immunoreactive clusters. In neonatal animals, Renshaw cells expressed small punctate gephyrin-immunoreactive clusters (mean cluster size ± SD = 0.19 ± 0.19 μm2at 2 days; 0.22 ± 0.19 μm2at 5 days). By 10 and 15 days of age, Renshaw cells exhibited gephyrin-immunoreactive clusters that were larger and more complex (0.32 ± 0.19 μm2 at 10 days; 0.41 ± 0.32 μm2 at 15 days). Cluster growth reached a plateau in 25- and 60-day-old Renshaw cells (0.45 ± 0.43 μm2; 0.56 ± 0.55 μm2, respectively). By using electron microscopy, we confirmed that gephyrin-immunoreactive clusters were located at postsynaptic sites at both early and late postnatal ages on Renshaw cells. The potential significance of this gephyrin/glycine receptor cluster size maturation that sets Renshaw cells apart from other interneurons is discussed. J. Comp. Neurol. 426:130–142, 2000. © 2000 Wiley-Liss, Inc.

DOI

10.1002/1096-9861(20001009)426:1<130::AID-CNE9>3.0.CO;2-7