The Journal of Neuroscience, January 1, 1999, 19(1):236-247
Stable Properties of Spontaneous EPSCs and Miniature Retinal
EPSCs during the Development of ON/OFF Sublamination in the Ferret
Lateral Geniculate Nucleus
Carsten D.
Hohnke and
Mriganka
Sur
Department of Brain and Cognitive Sciences, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139
Retinal projections to the lateral geniculate nucleus (LGN) in
ferrets progressively segregate into eye-specific laminae and subsequently into sublaminae that receive inputs from either ON-center or OFF-center afferents. To study the development of synaptic efficacy
during a period of activity-dependent growth and reorganization in the
CNS, we recorded spontaneous EPSCs (sEPSCs) from cells of the
LGN during ON/OFF sublamination. We also examined retinal inputs
specifically by stimulating the optic tract in the presence of
strontium and recording evoked miniature EPSCs (emEPSCs). The rise
times, areas, half-widths, and decay times of sEPSCs and emEPSCs and
interevent intervals of sEPSCs recorded at the beginning of ON/OFF
sublamination were not different from those recorded after its
completion. Typically EPSC areas were small (10-20 fC) but varied
greatly both within and between neurons. The frequency of sEPSCs was
also quite variable, ranging from 0.2 to 5 Hz. sEPSCs were equivalent
to miniature EPSCs recorded in the presence of tetrodotoxin, and both
sEPSCs and emEPSCs were CNQX-sensitive. No difference was observed
between sEPSCs recorded at room temperature and those recorded at
34°C, and strontium could be substituted for calcium with no effect
on sEPSC shape. These data argue for a remarkable stability in the
components of at least AMPA-mediated synaptic transmission during a
period of major synaptic rearrangement in the LGN.
Key words:
activity-dependent; pattern formation; AMPA-synapse; retinal axons; LTP; visual system
Copyright © 1999 Society for Neuroscience 0270-6474/99/191236-12$05.00/0