Journal of Neuroscience, Vol 9, 2163-2169, Copyright © 1989 by Society for Neuroscience
Distribution and lateral mobility of GABA/benzodiazepine receptors on nerve cells
JL Velazquez, CL Thompson, EM Barnes Jr and KJ Angelides
Department of Physiology, Baylor College of Medicine, Houston, Texas 77030.
The distribution and mobility of GABA/benzodiazepine receptors has been
examined on living nerve cells by fluorescence digital imaging and
fluorescence photobleach recovery with 2 novel fluorescent derivatives of
the benzodiazepines Ro7-1986 and 1012S. These fluorescent derivatives
retain their high affinity for the GABA/benzodiazepine receptor complex
with Ks of 79 and 85 nM, respectively. Digital fluorescence imaging of
GABA/benzodiazepine receptors on rat spinal cord neurons maintained in
culture reveal that, even in the absence of observable synaptic contact,
GABA/benzodiazepine receptors are localized on the cell body in clusters of
very high density. Receptor density on processes is lower than on cell
bodies, although occasional areas of intense fluorescence were observed.
Fluorescence photobleach recovery measurements show that 70% of the
GABA/benzodiazepine receptors on the cell body and greater than 85% on the
processes of rat spinal cord neurons are immobile. In comparison,
voltage-gated sodium channels are diffusely distributed and very mobile on
the cell body (D = 10(-9) cm2/sec). The results suggest that even in the
absence of nerve-nerve cell contact, there are specific mechanisms that
segregate GABA/benzodiazepine receptors to the neuronal cell body and
control their lateral mobility.