Journal of Neuroscience, Vol 10, 985-995, Copyright © 1990 by Society for Neuroscience
Distribution and lateral mobility of glycine receptors on cultured spinal cord neurons
Y Srinivasan, AP Guzikowski, RP Haugland and KJ Angelides
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Strychnine is one of the most potent antagonists of glycine-mediated
inhibitory conductances in the mammalian spinal cord. In order to examine
the distribution of glycine receptors (GlyRs) on neuronal cells, 2 novel
fluorescent strychnine derivatives were synthesized and characterized
chemically, spectroscopically, and biologically. Both compounds retain
their biological activity after derivatization and are potent inhibitors of
3H-strychnine binding to bovine spinal cord membranes and membranes from
rat spinal cord cultures. Using these fluorescent strychnine analogs, the
cellular distribution and lateral mobility of GlyRs on cultured rat spinal
cord neurons were studied by digital fluorescence imaging and photobleach
recovery microscopy. On these neurons, even in the absence of observable
synaptic contact and early in development GlyRs are predominantly localized
to cell bodies with sparse labeling of neuritic processes. Although GlyRs
are confined to the neuronal cell body, approximately 50% of the receptors
are very mobile, with lateral diffusion coefficients of 1.15 +/- 0.05 x
10(-9) cm2/sec, a value which is characteristic of unrestricted protein
lateral diffusion. However, the remaining fraction of these receptors are
immobile on the neuronal cell body. More than 70% of the GlyRs distributed
on neuronal processes are immobile, while 30% are laterally mobile, with
diffusion rates of 5.50 +/- 0.1 x 10(-10) cm2/sec. The results indicate
that even early in development GlyRs are expressed and segregated to the
cell body, where they are confined within a domain that restricts their
redistribution.